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PERL5160DELTA(1)		 Perl Programmers Reference Guide		 PERL5160DELTA(1)

       perl5160delta - what is new for perl v5.16.0

       This document describes differences between the 5.14.0 release and the 5.16.0 release.

       If you are upgrading from an earlier release such as 5.12.0, first read perl5140delta,
       which describes differences between 5.12.0 and 5.14.0.

       Some bug fixes in this release have been backported to later releases of 5.14.x.  Those
       are indicated with the 5.14.x version in parentheses.

       With the release of Perl 5.16.0, the 5.12.x series of releases is now out of its support
       period.	There may be future 5.12.x releases, but only in the event of a critical security
       issue.  Users of Perl 5.12 or earlier should consider upgrading to a more recent release
       of Perl.

       This policy is described in greater detail in perlpolicy.

Core Enhancements
   "use VERSION"
       As of this release, version declarations like "use v5.16" now disable all features before
       enabling the new feature bundle.  This means that the following holds true:

	   use 5.016;
	   # only 5.16 features enabled here
	   use 5.014;
	   # only 5.14 features enabled here (not 5.16)

       "use v5.12" and higher continue to enable strict, but explicit "use strict" and "no
       strict" now override the version declaration, even when they come first:

	   no strict;
	   use 5.012;
	   # no strict here

       There is a new ":default" feature bundle that represents the set of features enabled
       before any version declaration or "use feature" has been seen.  Version declarations below
       5.10 now enable the ":default" feature set.  This does not actually change the behavior of
       "use v5.8", because features added to the ":default" set are those that were traditionally
       enabled by default, before they could be turned off.

       "no feature" now resets to the default feature set.  To disable all features (which is
       likely to be a pretty special-purpose request, since it presumably won't match any named
       set of semantics) you can now write "no feature ':all'".

       $[ is now disabled under "use v5.16".  It is part of the default feature set and can be
       turned on or off explicitly with "use feature 'array_base'".

       The new "__SUB__" token, available under the "current_sub" feature (see feature) or "use
       v5.16", returns a reference to the current subroutine, making it easier to write recursive

   New and Improved Built-ins
       More consistent "eval"

       The "eval" operator sometimes treats a string argument as a sequence of characters and
       sometimes as a sequence of bytes, depending on the internal encoding.  The internal
       encoding is not supposed to make any difference, but there is code that relies on this

       The new "unicode_eval" and "evalbytes" features (enabled under "use 5.16.0") resolve this.
       The "unicode_eval" feature causes "eval $string" to treat the string always as Unicode.
       The "evalbytes" features provides a function, itself called "evalbytes", which evaluates
       its argument always as a string of bytes.

       These features also fix oddities with source filters leaking to outer dynamic scopes.

       See feature for more detail.

       "substr" lvalue revamp

       When "substr" is called in lvalue or potential lvalue context with two or three arguments,
       a special lvalue scalar is returned that modifies the original string (the first argument)
       when assigned to.

       Previously, the offsets (the second and third arguments) passed to "substr" would be
       converted immediately to match the string, negative offsets being translated to positive
       and offsets beyond the end of the string being truncated.

       Now, the offsets are recorded without modification in the special lvalue scalar that is
       returned, and the original string is not even looked at by "substr" itself, but only when
       the returned lvalue is read or modified.

       These changes result in an incompatible change:

       If the original string changes length after the call to "substr" but before assignment to
       its return value, negative offsets will remember their position from the end of the
       string, affecting code like this:

	   my $string = "string";
	   my $lvalue = \substr $string, -4, 2;
	   print $$lvalue, "\n"; # prints "ri"
	   $string = "bailing twine";
	   print $$lvalue, "\n"; # prints "wi"; used to print "il"

       The same thing happens with an omitted third argument.  The returned lvalue will always
       extend to the end of the string, even if the string becomes longer.

       Since this change also allowed many bugs to be fixed (see "The "substr" operator"), and
       since the behavior of negative offsets has never been specified, the change was deemed

       Return value of "tied"

       The value returned by "tied" on a tied variable is now the actual scalar that holds the
       object to which the variable is tied.  This lets ties be weakened with
       "Scalar::Util::weaken(tied $tied_variable)".

   Unicode Support
       Supports (almost) Unicode 6.1

       Besides the addition of whole new scripts, and new characters in existing scripts, this
       new version of Unicode, as always, makes some changes to existing characters.  One change
       that may trip up some applications is that the General Category of two characters in the
       Latin-1 range, PILCROW SIGN and SECTION SIGN, has been changed from Other_Symbol to
       Other_Punctuation.  The same change has been made for a character in each of Tibetan,
       Ethiopic, and Aegean.  The code points U+3248..U+324F (CIRCLED NUMBER TEN ON BLACK SQUARE
       through CIRCLED NUMBER EIGHTY ON BLACK SQUARE) have had their General Category changed
       from Other_Symbol to Other_Numeric.  The Line Break property has changes for Hebrew and
       Japanese; and because of other changes in 6.1, the Perl regular expression construct "\X"
       now works differently for some characters in Thai and Lao.

       New aliases (synonyms) have been defined for many property values; these, along with the
       previously existing ones, are all cross-indexed in perluniprops.

       The return value of "charnames::viacode()" is affected by other changes:

	Code point	Old Name	     New Name
	  U+0085    NEXT LINE (NEL)	  NEXT LINE
	  U+0091    PRIVATE USE 1	  PRIVATE USE-1
	  U+0092    PRIVATE USE 2	  PRIVATE USE-2

       Perl will accept any of these names as input, but "charnames::viacode()" now returns the
       new name of each pair.  The change for U+2118 is considered by Unicode to be a correction,
       that is the original name was a mistake (but again, it will remain forever valid to use it
       to refer to U+2118).  But most of these changes are the fallout of the mistake Unicode 6.0
       made in naming a character used in Japanese cell phones to be "BELL", which conflicts with
       the longstanding industry use of (and Unicode's recommendation to use) that name to mean
       the ASCII control character at U+0007.  Therefore, that name has been deprecated in Perl
       since v5.14, and any use of it will raise a warning message (unless turned off).  The name
       "ALERT" is now the preferred name for this code point, with "BEL" an acceptable short
       form.  The name for the new cell phone character, at code point U+1F514, remains undefined
       in this version of Perl (hence we don't implement quite all of Unicode 6.1), but starting
       in v5.18, BELL will mean this character, and not U+0007.

       Unicode has taken steps to make sure that this sort of mistake does not happen again.  The
       Standard now includes all generally accepted names and abbreviations for control
       characters, whereas previously it didn't (though there were recommended names for most of
       them, which Perl used).	This means that most of those recommended names are now
       officially in the Standard.  Unicode did not recommend names for the four code points
       listed above between U+008E and U+008F, and in standardizing them Unicode subtly changed
       the names that Perl had previously given them, by replacing the final blank in each name
       by a hyphen.  Unicode also officially accepts names that Perl had deprecated, such as FILE
       SEPARATOR.  Now the only deprecated name is BELL.  Finally, Perl now uses the new official
       names instead of the old (now considered obsolete) names for the first four code points in
       the list above (the ones which have the parentheses in them).

       Now that the names have been placed in the Unicode standard, these kinds of changes should
       not happen again, though corrections, such as to U+2118, are still possible.

       Unicode also added some name abbreviations, which Perl now accepts: SP for SPACE; TAB for

       More details on this version of Unicode are provided in

       "use charnames" is no longer needed for "\N{name}"

       When "\N{name}" is encountered, the "charnames" module is now automatically loaded when
       needed as if the ":full" and ":short" options had been specified.  See charnames for more

       "\N{...}" can now have Unicode loose name matching

       This is described in the "charnames" item in "Updated Modules and Pragmata" below.

       Unicode Symbol Names

       Perl now has proper support for Unicode in symbol names.  It used to be that "*{$foo}"
       would ignore the internal UTF8 flag and use the bytes of the underlying representation to
       look up the symbol.  That meant that "*{"\x{100}"}" and "*{"\xc4\x80"}" would return the
       same thing.  All these parts of Perl have been fixed to account for Unicode:

       o   Method names (including those passed to "use overload")

       o   Typeglob names (including names of variables, subroutines, and filehandles)

       o   Package names

       o   "goto"

       o   Symbolic dereferencing

       o   Second argument to "bless()" and "tie()"

       o   Return value of "ref()"

       o   Subroutine prototypes

       o   Attributes

       o   Various warnings and error messages that mention variable names or values, methods,

       In addition, a parsing bug has been fixed that prevented "*{e}" from implicitly quoting
       the name, but instead interpreted it as "*{+e}", which would cause a strict violation.

       "*{"*a::b"}" automatically strips off the * if it is followed by an ASCII letter.  That
       has been extended to all Unicode identifier characters.

       One-character non-ASCII non-punctuation variables (like "$e") are now subject to "Used
       only once" warnings.  They used to be exempt, as they were treated as punctuation

       Also, single-character Unicode punctuation variables (like $X) are now supported [perl

       Improved ability to mix locales and Unicode, including UTF-8 locales

       An optional parameter has been added to "use locale"

	use locale ':not_characters';

       which tells Perl to use all but the "LC_CTYPE" and "LC_COLLATE" portions of the current
       locale.	Instead, the character set is assumed to be Unicode.  This lets locales and
       Unicode be seamlessly mixed, including the increasingly frequent UTF-8 locales.	When
       using this hybrid form of locales, the ":locale" layer to the open pragma can be used to
       interface with the file system, and there are CPAN modules available for ARGV and
       environment variable conversions.

       Full details are in perllocale.

       New function "fc" and corresponding escape sequence "\F" for Unicode foldcase

       Unicode foldcase is an extension to lowercase that gives better results when comparing two
       strings case-insensitively.  It has long been used internally in regular expression "/i"
       matching.  Now it is available explicitly through the new "fc" function call (enabled by
       "use feature 'fc'", or "use v5.16", or explicitly callable via "CORE::fc") or through the
       new "\F" sequence in double-quotish strings.

       Full details are in "fc" in perlfunc.

       The Unicode "Script_Extensions" property is now supported.

       New in Unicode 6.0, this is an improved "Script" property.  Details are in "Scripts" in

   XS Changes
       Improved typemaps for Some Builtin Types

       Most XS authors will know there is a longstanding bug in the OUTPUT typemap for T_AVREF
       ("AV*"), T_HVREF ("HV*"), T_CVREF ("CV*"), and T_SVREF ("SVREF" or "\$foo") that requires
       manually decrementing the reference count of the return value instead of the typemap
       taking care of this.  For backwards-compatibility, this cannot be changed in the default
       typemaps.  But we now provide additional typemaps "T_AVREF_REFCOUNT_FIXED", etc. that do
       not exhibit this bug.  Using them in your extension is as simple as having one line in
       your "TYPEMAP" section:



       The XS-callable function "is_utf8_char()", when presented with malformed UTF-8 input, can
       read up to 12 bytes beyond the end of the string.  This cannot be fixed without changing
       its API, and so its use is now deprecated.  Use "is_utf8_char_buf()" (described just
       below) instead.

       Added "is_utf8_char_buf()"

       This function is designed to replace the deprecated "is_utf8_char()" function.  It
       includes an extra parameter to make sure it doesn't read past the end of the input buffer.

       Other "is_utf8_foo()" functions, as well as "utf8_to_foo()", etc.

       Most other XS-callable functions that take UTF-8 encoded input implicitly assume that the
       UTF-8 is valid (not malformed) with respect to buffer length.  Do not do things such as
       change a character's case or see if it is alphanumeric without first being sure that it is
       valid UTF-8.  This can be safely done for a whole string by using one of the functions
       "is_utf8_string()", "is_utf8_string_loc()", and "is_utf8_string_loclen()".

       New Pad API

       Many new functions have been added to the API for manipulating lexical pads.  See "Pad
       Data Structures" in perlapi for more information.

   Changes to Special Variables
       $$ can be assigned to

       $$ was made read-only in Perl 5.8.0.  But only sometimes: "local $$" would make it
       writable again.	Some CPAN modules were using "local $$" or XS code to bypass the read-
       only check, so there is no reason to keep $$ read-only.	(This change also allowed a bug
       to be fixed while maintaining backward compatibility.)

       $^X converted to an absolute path on FreeBSD, OS X and Solaris

       $^X is now converted to an absolute path on OS X, FreeBSD (without needing /proc mounted)
       and Solaris 10 and 11.  This augments the previous approach of using /proc on Linux,
       FreeBSD, and NetBSD (in all cases, where mounted).

       This makes relocatable perl installations more useful on these platforms.  (See
       "Relocatable @INC" in INSTALL)

   Debugger Changes
       Features inside the debugger

       The current Perl's feature bundle is now enabled for commands entered in the interactive

       New option for the debugger's t command

       The t command in the debugger, which toggles tracing mode, now accepts a numeric argument
       that determines how many levels of subroutine calls to trace.

       "enable" and "disable"

       The debugger now has "disable" and "enable" commands for disabling existing breakpoints
       and re-enabling them.  See perldebug.

       Breakpoints with file names

       The debugger's "b" command for setting breakpoints now lets a line number be prefixed with
       a file name.  See "b [file]:[line] [condition]" in perldebug.

   The "CORE" Namespace
       The "CORE::" prefix

       The "CORE::" prefix can now be used on keywords enabled by feature.pm, even outside the
       scope of "use feature".

       Subroutines in the "CORE" namespace

       Many Perl keywords are now available as subroutines in the CORE namespace.  This lets them
       be aliased:

	   BEGIN { *entangle = \&CORE::tie }
	   entangle $variable, $package, @args;

       And for prototypes to be bypassed:

	   sub mytie(\[%$*@]$@) {
	       my ($ref, $pack, @args) = @_;
	       ... do something ...
	       goto &CORE::tie;

       Some of these cannot be called through references or via &foo syntax, but must be called
       as barewords.

       See CORE for details.

   Other Changes
       Anonymous handles

       Automatically generated file handles are now named __ANONIO__ when the variable name
       cannot be determined, rather than $__ANONIO__.

       Autoloaded sort Subroutines

       Custom sort subroutines can now be autoloaded [perl #30661]:

	   sub AUTOLOAD { ... }
	   @sorted = sort foo @list; # uses AUTOLOAD

       "continue" no longer requires the "switch" feature

       The "continue" keyword has two meanings.  It can introduce a "continue" block after a
       loop, or it can exit the current "when" block.  Up to now, the latter meaning was valid
       only with the "switch" feature enabled, and was a syntax error otherwise.  Since the main
       purpose of feature.pm is to avoid conflicts with user-defined subroutines, there is no
       reason for "continue" to depend on it.

       DTrace probes for interpreter phase change

       The "phase-change" probes will fire when the interpreter's phase changes, which tracks the
       "${^GLOBAL_PHASE}" variable.  "arg0" is the new phase name; "arg1" is the old one.  This
       is useful for limiting your instrumentation to one or more of: compile time, run time, or
       destruct time.

       "__FILE__()" Syntax

       The "__FILE__", "__LINE__" and "__PACKAGE__" tokens can now be written with an empty pair
       of parentheses after them.  This makes them parse the same way as "time", "fork" and other
       built-in functions.

       The "\$" prototype accepts any scalar lvalue

       The "\$" and "\[$]" subroutine prototypes now accept any scalar lvalue argument.
       Previously they accepted only scalars beginning with "$" and hash and array elements.
       This change makes them consistent with the way the built-in "read" and "recv" functions
       (among others) parse their arguments.  This means that one can override the built-in
       functions with custom subroutines that parse their arguments the same way.

       "_" in subroutine prototypes

       The "_" character in subroutine prototypes is now allowed before "@" or "%".

   Use "is_utf8_char_buf()" and not "is_utf8_char()"
       The latter function is now deprecated because its API is insufficient to guarantee that it
       doesn't read (up to 12 bytes in the worst case) beyond the end of its input string.  See

   Malformed UTF-8 input could cause attempts to read beyond the end of the buffer
       Two new XS-accessible functions, "utf8_to_uvchr_buf()" and "utf8_to_uvuni_buf()" are now
       available to prevent this, and the Perl core has been converted to use them.  See
       "Internal Changes".

   "File::Glob::bsd_glob()" memory error with GLOB_ALTDIRFUNC (CVE-2011-2728).
       Calling "File::Glob::bsd_glob" with the unsupported flag GLOB_ALTDIRFUNC would cause an
       access violation / segfault.  A Perl program that accepts a flags value from an external
       source could expose itself to denial of service or arbitrary code execution attacks.
       There are no known exploits in the wild.  The problem has been corrected by explicitly
       disabling all unsupported flags and setting unused function pointers to null.  Bug
       reported by Clement Lecigne. (5.14.2)

   Privileges are now set correctly when assigning to $(
       A hypothetical bug (probably unexploitable in practice) because the incorrect setting of
       the effective group ID while setting $( has been fixed.	The bug would have affected only
       systems that have "setresgid()" but not "setregid()", but no such systems are known to

   Don't read the Unicode data base files in lib/unicore
       It is now deprecated to directly read the Unicode data base files.  These are stored in
       the lib/unicore directory.  Instead, you should use the new functions in Unicode::UCD.
       These provide a stable API, and give complete information.

       Perl may at some point in the future change or remove these files.  The file which
       applications were most likely to have used is lib/unicore/ToDigit.pl.  "prop_invmap()" in
       Unicode::UCD can be used to get at its data instead.

   XS functions "is_utf8_char()", "utf8_to_uvchr()" and "utf8_to_uvuni()"
       This function is deprecated because it could read beyond the end of the input string.  Use
       the new is_utf8_char_buf(), "utf8_to_uvchr_buf()" and "utf8_to_uvuni_buf()" instead.

Future Deprecations
       This section serves as a notice of features that are likely to be removed or deprecated in
       the next release of perl (5.18.0).  If your code depends on these features, you should
       contact the Perl 5 Porters via the mailing list
       <http://lists.perl.org/list/perl5-porters.html> or perlbug to explain your use case and
       inform the deprecation process.

   Core Modules
       These modules may be marked as deprecated from the core.  This only means that they will
       no longer be installed by default with the core distribution, but will remain available on
       the CPAN.

       o   CPANPLUS

       o   Filter::Simple

       o   PerlIO::mmap

       o   Pod::LaTeX

       o   Pod::Parser

       o   SelfLoader

       o   Text::Soundex

       o   Thread.pm

   Platforms with no supporting programmers:
       These platforms will probably have their special build support removed during the 5.17.0
       development series.

       o   BeOS

       o   djgpp

       o   dgux

       o   EPOC

       o   MPE/iX

       o   Rhapsody

       o   UTS

       o   VM/ESA

   Other Future Deprecations
       o   Swapping of $< and $>

	   For more information about this future deprecation, see the relevant RT ticket

       o   sfio, stdio

	   Perl supports being built without PerlIO proper, using a stdio or sfio wrapper
	   instead.  A perl build like this will not support IO layers and thus Unicode IO,
	   making it rather handicapped.

	   PerlIO supports a "stdio" layer if stdio use is desired, and similarly a sfio layer
	   could be produced.

       o   Unescaped literal "{" in regular expressions.

	   Starting with v5.20, it is planned to require a literal "{" to be escaped, for example
	   by preceding it with a backslash.  In v5.18, a deprecated warning message will be
	   emitted for all such uses.  This affects only patterns that are to match a literal
	   "{".  Other uses of this character, such as part of a quantifier or sequence as in
	   those below, are completely unaffected:

	       /\N{DIGIT ZERO}

	   Removing this will permit extensions to Perl's pattern syntax and better error
	   checking for existing syntax.  See "Quantifiers" in perlre for an example.

       o   Revamping "\Q" semantics in double-quotish strings when combined with other escapes.

	   There are several bugs and inconsistencies involving combinations of "\Q" and escapes
	   like "\x", "\L", etc., within a "\Q...\E" pair.  These need to be fixed, and doing so
	   will necessarily change current behavior.  The changes have not yet been settled.

Incompatible Changes
   Special blocks called in void context
       Special blocks ("BEGIN", "CHECK", "INIT", "UNITCHECK", "END") are now called in void
       context.  This avoids wasteful copying of the result of the last statement [perl #108794].

   The "overloading" pragma and regexp objects
       With "no overloading", regular expression objects returned by "qr//" are now stringified
       as "Regexp=REGEXP(0xbe600d)" instead of the regular expression itself [perl #108780].

   Two XS typemap Entries removed
       Two presumably unused XS typemap entries have been removed from the core typemap:
       T_DATAUNIT and T_CALLBACK.  If you are, against all odds, a user of these, please see the
       instructions on how to restore them in perlxstypemap.

   Unicode 6.1 has incompatibilities with Unicode 6.0
       These are detailed in "Supports (almost) Unicode 6.1" above.  You can compile this version
       of Perl to use Unicode 6.0.  See "Hacking Perl to work on earlier Unicode versions (for
       very serious hackers only)" in perlunicode.

   Borland compiler
       All support for the Borland compiler has been dropped.  The code had not worked for a long
       time anyway.

   Certain deprecated Unicode properties are no longer supported by default
       Perl should never have exposed certain Unicode properties that are used by Unicode
       internally and not meant to be publicly available.  Use of these has generated deprecated
       warning messages since Perl 5.12.  The removed properties are Other_Alphabetic,
       Other_Default_Ignorable_Code_Point, Other_Grapheme_Extend, Other_ID_Continue,
       Other_ID_Start, Other_Lowercase, Other_Math, and Other_Uppercase.

       Perl may be recompiled to include any or all of them; instructions are given in "Unicode
       character properties that are NOT accepted by Perl" in perluniprops.

   Dereferencing IO thingies as typeglobs
       The "*{...}" operator, when passed a reference to an IO thingy (as in "*{*STDIN{IO}}"),
       creates a new typeglob containing just that IO object.  Previously, it would stringify as
       an empty string, but some operators would treat it as undefined, producing an
       "uninitialized" warning.  Now it stringifies as __ANONIO__ [perl #96326].

   User-defined case-changing operations
       This feature was deprecated in Perl 5.14, and has now been removed.  The CPAN module
       Unicode::Casing provides better functionality without the drawbacks that this feature had,
       as are detailed in the 5.14 documentation:

   XSUBs are now 'static'
       XSUB C functions are now 'static', that is, they are not visible from outside the
       compilation unit.  Users can use the new "XS_EXTERNAL(name)" and "XS_INTERNAL(name)"
       macros to pick the desired linking behavior.  The ordinary "XS(name)" declaration for
       XSUBs will continue to declare non-'static' XSUBs for compatibility, but the XS compiler,
       ExtUtils::ParseXS ("xsubpp") will emit 'static' XSUBs by default.  ExtUtils::ParseXS's
       behavior can be reconfigured from XS using the "EXPORT_XSUB_SYMBOLS" keyword.  See perlxs
       for details.

   Weakening read-only references
       Weakening read-only references is no longer permitted.  It should never have worked
       anyway, and could sometimes result in crashes.

   Tying scalars that hold typeglobs
       Attempting to tie a scalar after a typeglob was assigned to it would instead tie the
       handle in the typeglob's IO slot.  This meant that it was impossible to tie the scalar
       itself.	Similar problems affected "tied" and "untie": "tied $scalar" would return false
       on a tied scalar if the last thing returned was a typeglob, and "untie $scalar" on such a
       tied scalar would do nothing.

       We fixed this problem before Perl 5.14.0, but it caused problems with some CPAN modules,
       so we put in a deprecation cycle instead.

       Now the deprecation has been removed and this bug has been fixed.  So "tie $scalar" will
       always tie the scalar, not the handle it holds.	To tie the handle, use "tie *$scalar"
       (with an explicit asterisk).  The same applies to "tied *$scalar" and "untie *$scalar".

   IPC::Open3 no longer provides "xfork()", "xclose_on_exec()" and "xpipe_anon()"
       All three functions were private, undocumented, and unexported.	They do not appear to be
       used by any code on CPAN.  Two have been inlined and one deleted entirely.

   $$ no longer caches PID
       Previously, if one called fork(3) from C, Perl's notion of $$ could go out of sync with
       what getpid() returns.  By always fetching the value of $$ via getpid(), this potential
       bug is eliminated.  Code that depends on the caching behavior will break.  As described in
       Core Enhancements, $$ is now writable, but it will be reset during a fork.

   $$ and "getppid()" no longer emulate POSIX semantics under LinuxThreads
       The POSIX emulation of $$ and "getppid()" under the obsolete LinuxThreads implementation
       has been removed.  This only impacts users of Linux 2.4 and users of Debian GNU/kFreeBSD
       up to and including 6.0, not the vast majority of Linux installations that use NPTL

       This means that "getppid()", like $$, is now always guaranteed to return the OS's idea of
       the current state of the process, not perl's cached version of it.

       See the documentation for $$ for details.

   $<, $>, $( and $) are no longer cached
       Similarly to the changes to $$ and "getppid()", the internal caching of $<, $>, $( and $)
       has been removed.

       When we cached these values our idea of what they were would drift out of sync with
       reality if someone (e.g., someone embedding perl) called "sete?[ug]id()" without updating
       "PL_e?[ug]id".  Having to deal with this complexity wasn't worth it given how cheap the
       "gete?[ug]id()" system call is.

       This change will break a handful of CPAN modules that use the XS-level "PL_uid", "PL_gid",
       "PL_euid" or "PL_egid" variables.

       The fix for those breakages is to use "PerlProc_gete?[ug]id()" to retrieve them (e.g.,
       "PerlProc_getuid()"), and not to assign to "PL_e?[ug]id" if you change the
       UID/GID/EUID/EGID.  There is no longer any need to do so since perl will always retrieve
       the up-to-date version of those values from the OS.

   Which Non-ASCII characters get quoted by "quotemeta" and "\Q" has changed
       This is unlikely to result in a real problem, as Perl does not attach special meaning to
       any non-ASCII character, so it is currently irrelevant which are quoted or not.	This
       change fixes bug [perl #77654] and brings Perl's behavior more into line with Unicode's
       recommendations.  See "quotemeta" in perlfunc.

Performance Enhancements
       o   Improved performance for Unicode properties in regular expressions

	   Matching a code point against a Unicode property is now done via a binary search
	   instead of linear.  This means for example that the worst case for a 1000 item
	   property is 10 probes instead of 1000.  This inefficiency has been compensated for in
	   the past by permanently storing in a hash the results of a given probe plus the
	   results for the adjacent 64 code points, under the theory that near-by code points are
	   likely to be searched for.  A separate hash was used for each mention of a Unicode
	   property in each regular expression.  Thus, "qr/\p{foo}abc\p{foo}/" would generate two
	   hashes.  Any probes in one instance would be unknown to the other, and the hashes
	   could expand separately to be quite large if the regular expression were used on many
	   different widely-separated code points.  Now, however, there is just one hash shared
	   by all instances of a given property.  This means that if "\p{foo}" is matched against
	   "A" in one regular expression in a thread, the result will be known immediately to all
	   regular expressions, and the relentless march of using up memory is slowed

       o   Version declarations with the "use" keyword (e.g., "use 5.012") are now faster, as
	   they enable features without loading feature.pm.

       o   "local $_" is faster now, as it no longer iterates through magic that it is not going
	   to copy anyway.

       o   Perl 5.12.0 sped up the destruction of objects whose classes define empty "DESTROY"
	   methods (to prevent autoloading), by simply not calling such empty methods.	This
	   release takes this optimization a step further, by not calling any "DESTROY" method
	   that begins with a "return" statement.  This can be useful for destructors that are
	   only used for debugging:

	       use constant DEBUG => 1;
	       sub DESTROY { return unless DEBUG; ... }

	   Constant-folding will reduce the first statement to "return;" if DEBUG is set to 0,
	   triggering this optimization.

       o   Assigning to a variable that holds a typeglob or copy-on-write scalar is now much
	   faster.  Previously the typeglob would be stringified or the copy-on-write scalar
	   would be copied before being clobbered.

       o   Assignment to "substr" in void context is now more than twice its previous speed.
	   Instead of creating and returning a special lvalue scalar that is then assigned to,
	   "substr" modifies the original string itself.

       o   "substr" no longer calculates a value to return when called in void context.

       o   Due to changes in File::Glob, Perl's "glob" function and its "<...>" equivalent are
	   now much faster.  The splitting of the pattern into words has been rewritten in C,
	   resulting in speed-ups of 20% for some cases.

	   This does not affect "glob" on VMS, as it does not use File::Glob.

       o   The short-circuiting operators "&&", "||", and "//", when chained (such as "$a || $b
	   || $c"), are now considerably faster to short-circuit, due to reduced optree

       o   The implementation of "s///r" makes one fewer copy of the scalar's value.

       o   Recursive calls to lvalue subroutines in lvalue scalar context use less memory.

Modules and Pragmata
   Deprecated Modules
	   Version::Requirements is now DEPRECATED, use CPAN::Meta::Requirements, which is a
	   drop-in replacement.  It will be deleted from perl.git blead in v5.17.0.

   New Modules and Pragmata
       o   arybase -- this new module implements the $[ variable.

       o   PerlIO::mmap 0.010 has been added to the Perl core.

	   The "mmap" PerlIO layer is no longer implemented by perl itself, but has been moved
	   out into the new PerlIO::mmap module.

   Updated Modules and Pragmata
       This is only an overview of selected module updates.  For a complete list of updates, run:

	   $ corelist --diff 5.14.0 5.16.0

       You can substitute your favorite version in place of 5.14.0, too.

       o   Archive::Extract has been upgraded from version 0.48 to 0.58.

	   Includes a fix for FreeBSD to only use "unzip" if it is located in "/usr/local/bin",
	   as FreeBSD 9.0 will ship with a limited "unzip" in "/usr/bin".

       o   Archive::Tar has been upgraded from version 1.76 to 1.82.

	   Adjustments to handle files >8gb (>0777777777777 octal) and a feature to return the
	   MD5SUM of files in the archive.

       o   base has been upgraded from version 2.16 to 2.18.

	   "base" no longer sets a module's $VERSION to "-1" when a module it loads does not
	   define a $VERSION.  This change has been made because "-1" is not a valid version
	   number under the new "lax" criteria used internally by "UNIVERSAL::VERSION".  (See
	   version for more on "lax" version criteria.)

	   "base" no longer internally skips loading modules it has already loaded and instead
	   relies on "require" to inspect %INC.  This fixes a bug when "base" is used with code
	   that clear %INC to force a module to be reloaded.

       o   Carp has been upgraded from version 1.20 to 1.26.

	   It now includes last read filehandle info and puts a dot after the file and line
	   number, just like errors from "die" [perl #106538].

       o   charnames has been updated from version 1.18 to 1.30.

	   "charnames" can now be invoked with a new option, ":loose", which is like the existing
	   ":full" option, but enables Unicode loose name matching.  Details are in "LOOSE
	   MATCHES" in charnames.

       o   B::Deparse has been upgraded from version 1.03 to 1.14.  This fixes numerous deparsing

       o   CGI has been upgraded from version 3.52 to 3.59.

	   It uses the public and documented FCGI.pm API in CGI::Fast.	CGI::Fast was using an
	   FCGI API that was deprecated and removed from documentation more than ten years ago.
	   Usage of this deprecated API with FCGI >= 0.70 or FCGI <= 0.73 introduces a security
	   issue.  <https://rt.cpan.org/Public/Bug/Display.html?id=68380>

	   Things that may break your code:

	   "url()" was fixed to return "PATH_INFO" when it is explicitly requested with either
	   the "path=>1" or "path_info=>1" flag.

	   If your code is running under mod_rewrite (or compatible) and you are calling
	   "self_url()" or you are calling "url()" and passing "path_info=>1", these methods will
	   actually be returning "PATH_INFO" now, as you have explicitly requested or
	   "self_url()" has requested on your behalf.

	   The "PATH_INFO" has been omitted in such URLs since the issue was introduced in the
	   3.12 release in December, 2005.

	   This bug is so old your application may have come to depend on it or workaround it.
	   Check for application before upgrading to this release.

	   Examples of affected method calls:

	     $q->url(-absolute => 1, -query => 1, -path_info => 1);

	   We no longer read from STDIN when the Content-Length is not set, preventing requests
	   with no Content-Length from sometimes freezing.  This is consistent with the CGI RFC
	   3875, and is also consistent with CGI::Simple.  However, the old behavior may have
	   been expected by some command-line uses of CGI.pm.

	   In addition, the DELETE HTTP verb is now supported.

       o   Compress::Zlib has been upgraded from version 2.035 to 2.048.

	   IO::Compress::Zip and IO::Uncompress::Unzip now have support for LZMA (method 14).
	   There is a fix for a CRC issue in IO::Compress::Unzip and it supports Streamed Stored
	   context now.  And fixed a Zip64 issue in IO::Compress::Zip when the content size was
	   exactly 0xFFFFFFFF.

       o   Digest::SHA has been upgraded from version 5.61 to 5.71.

	   Added BITS mode to the addfile method and shasum.  This makes partial-byte inputs
	   possible via files/STDIN and lets shasum check all 8074 NIST Msg vectors, where
	   previously special programming was required to do this.

       o   Encode has been upgraded from version 2.42 to 2.44.

	   Missing aliases added, a deep recursion error fixed and various documentation updates.

	   Addressed 'decode_xs n-byte heap-overflow' security bug in Unicode.xs (CVE-2011-2939).

       o   ExtUtils::CBuilder updated from version 0.280203 to 0.280206.

	   The new version appends CFLAGS and LDFLAGS to their Config.pm counterparts.

       o   ExtUtils::ParseXS has been upgraded from version 2.2210 to 3.16.

	   Much of ExtUtils::ParseXS, the module behind the XS compiler "xsubpp", was rewritten
	   and cleaned up.  It has been made somewhat more extensible and now finally uses

	   The typemap logic has been moved into a separate module, ExtUtils::Typemaps.  See "New
	   Modules and Pragmata", above.

	   For a complete set of changes, please see the ExtUtils::ParseXS changelog, available
	   on the CPAN.

       o   File::Glob has been upgraded from version 1.12 to 1.17.

	   On Windows, tilde (~) expansion now checks the "USERPROFILE" environment variable,
	   after checking "HOME".

	   It has a new ":bsd_glob" export tag, intended to replace ":glob".  Like ":glob" it
	   overrides "glob" with a function that does not split the glob pattern into words, but,
	   unlike ":glob", it iterates properly in scalar context, instead of returning the last

	   There are other changes affecting Perl's own "glob" operator (which uses File::Glob
	   internally, except on VMS).	See "Performance Enhancements" and "Selected Bug Fixes".

       o   FindBin updated from version 1.50 to 1.51.

	   It no longer returns a wrong result if a script of the same name as the current one
	   exists in the path and is executable.

       o   HTTP::Tiny has been upgraded from version 0.012 to 0.017.

	   Added support for using $ENV{http_proxy} to set the default proxy host.

	   Adds additional shorthand methods for all common HTTP verbs, a "post_form()" method
	   for POST-ing x-www-form-urlencoded data and a "www_form_urlencode()" utility method.

       o   IO has been upgraded from version 1.25_04 to 1.25_06, and IO::Handle from version 1.31
	   to 1.33.

	   Together, these upgrades fix a problem with IO::Handle's "getline" and "getlines"
	   methods.  When these methods are called on the special ARGV handle, the next file is
	   automatically opened, as happens with the built-in "<>" and "readline" functions.
	   But, unlike the built-ins, these methods were not respecting the caller's use of the
	   open pragma and applying the appropriate I/O layers to the newly-opened file
	   [rt.cpan.org #66474].

       o   IPC::Cmd has been upgraded from version 0.70 to 0.76.

	   Capturing of command output (both "STDOUT" and "STDERR") is now supported using
	   IPC::Open3 on MSWin32 without requiring IPC::Run.

       o   IPC::Open3 has been upgraded from version 1.09 to 1.12.

	   Fixes a bug which prevented use of "open3" on Windows when *STDIN, *STDOUT or *STDERR
	   had been localized.

	   Fixes a bug which prevented duplicating numeric file descriptors on Windows.

	   "open3" with "-" for the program name works once more.  This was broken in version
	   1.06 (and hence in Perl 5.14.0) [perl #95748].

       o   Locale::Codes has been upgraded from version 3.16 to 3.21.

	   Added Language Extension codes (langext) and Language Variation codes (langvar) as
	   defined in the IANA language registry.

	   Added language codes from ISO 639-5

	   Added language/script codes from the IANA language subtag registry

	   Fixed an uninitialized value warning [rt.cpan.org #67438].

	   Fixed the return value for the all_XXX_codes and all_XXX_names functions [rt.cpan.org

	   Reorganized modules to move Locale::MODULE to Locale::Codes::MODULE to allow for
	   cleaner future additions.  The original four modules (Locale::Language,
	   Locale::Currency, Locale::Country, Locale::Script) will continue to work, but all new
	   sets of codes will be added in the Locale::Codes namespace.

	   The code2XXX, XXX2code, all_XXX_codes, and all_XXX_names functions now support retired
	   codes.  All codesets may be specified by a constant or by their name now.  Previously,
	   they were specified only by a constant.

	   The alias_code function exists for backward compatibility.  It has been replaced by
	   rename_country_code.  The alias_code function will be removed some time after
	   September, 2013.

	   All work is now done in the central module (Locale::Codes).	Previously, some was
	   still done in the wrapper modules (Locale::Codes::*).  Added Language Family codes
	   (langfam) as defined in ISO 639-5.

       o   Math::BigFloat has been upgraded from version 1.993 to 1.997.

	   The "numify" method has been corrected to return a normalized Perl number (the result
	   of "0 + $thing"), instead of a string [rt.cpan.org #66732].

       o   Math::BigInt has been upgraded from version 1.994 to 1.998.

	   It provides a new "bsgn" method that complements the "babs" method.

	   It fixes the internal "objectify" function's handling of "foreign objects" so they are
	   converted to the appropriate class (Math::BigInt or Math::BigFloat).

       o   Math::BigRat has been upgraded from version 0.2602 to 0.2603.

	   "int()" on a Math::BigRat object containing -1/2 now creates a Math::BigInt containing
	   0, rather than -0.  Math::BigInt does not even support negative zero, so the resulting
	   object was actually malformed [perl #95530].

       o   Math::Complex has been upgraded from version 1.56 to 1.59 and Math::Trig from version
	   1.2 to 1.22.

	   Fixes include: correct copy constructor usage; fix polarwise formatting with numeric
	   format specifier; and more stable "great_circle_direction" algorithm.

       o   Module::CoreList has been upgraded from version 2.51 to 2.66.

	   The "corelist" utility now understands the "-r" option for displaying Perl release
	   dates and the "--diff" option to print the set of modlib changes between two perl

       o   Module::Metadata has been upgraded from version 1.000004 to 1.000009.

	   Adds "provides" method to generate a CPAN META provides data structure correctly; use
	   of "package_versions_from_directory" is discouraged.

       o   ODBM_File has been upgraded from version 1.10 to 1.12.

	   The XS code is now compiled with "PERL_NO_GET_CONTEXT", which will aid performance
	   under ithreads.

       o   open has been upgraded from version 1.08 to 1.10.

	   It no longer turns off layers on standard handles when invoked without the ":std"
	   directive.  Similarly, when invoked with the ":std" directive, it now clears layers on
	   STDERR before applying the new ones, and not just on STDIN and STDOUT [perl #92728].

       o   overload has been upgraded from version 1.13 to 1.18.

	   "overload::Overloaded" no longer calls "can" on the class, but uses another means to
	   determine whether the object has overloading.  It was never correct for it to call
	   "can", as overloading does not respect AUTOLOAD.  So classes that autoload methods and
	   implement "can" no longer have to account for overloading [perl #40333].

	   A warning is now produced for invalid arguments.  See "New Diagnostics".

       o   PerlIO::scalar has been upgraded from version 0.11 to 0.14.

	   (This is the module that implements "open $fh, '>', \$scalar".)

	   It fixes a problem with "open my $fh, ">", \$scalar" not working if $scalar is a copy-
	   on-write scalar. (5.14.2)

	   It also fixes a hang that occurs with "readline" or "<$fh>" if a typeglob has been
	   assigned to $scalar [perl #92258].

	   It no longer assumes during "seek" that $scalar is a string internally.  If it didn't
	   crash, it was close to doing so [perl #92706].  Also, the internal print routine no
	   longer assumes that the position set by "seek" is valid, but extends the string to
	   that position, filling the intervening bytes (between the old length and the seek
	   position) with nulls [perl #78980].

	   Printing to an in-memory handle now works if the $scalar holds a reference,
	   stringifying the reference before modifying it.  References used to be treated as
	   empty strings.

	   Printing to an in-memory handle no longer crashes if the $scalar happens to hold a
	   number internally, but no string buffer.

	   Printing to an in-memory handle no longer creates scalars that confuse the regular
	   expression engine [perl #108398].

       o   Pod::Functions has been upgraded from version 1.04 to 1.05.

	   Functions.pm is now generated at perl build time from annotations in perlfunc.pod.
	   This will ensure that Pod::Functions and perlfunc remain in synchronisation.

       o   Pod::Html has been upgraded from version 1.11 to 1.1502.

	   This is an extensive rewrite of Pod::Html to use Pod::Simple under the hood.  The
	   output has changed significantly.

       o   Pod::Perldoc has been upgraded from version 3.15_03 to 3.17.

	   It corrects the search paths on VMS [perl #90640]. (5.14.1)

	   The -v option now fetches the right section for $0.

	   This upgrade has numerous significant fixes.  Consult its changelog on the CPAN for
	   more information.

       o   POSIX has been upgraded from version 1.24 to 1.30.

	   POSIX no longer uses AutoLoader.  Any code which was relying on this implementation
	   detail was buggy, and may fail because of this change.  The module's Perl code has
	   been considerably simplified, roughly halving the number of lines, with no change in
	   functionality.  The XS code has been refactored to reduce the size of the shared
	   object by about 12%, with no change in functionality.  More POSIX functions now have

	   "sigsuspend" and "pause" now run signal handlers before returning, as the whole point
	   of these two functions is to wait until a signal has arrived, and then return after it
	   has been triggered.	Delayed, or "safe", signals were preventing that from happening,
	   possibly resulting in race conditions [perl #107216].

	   "POSIX::sleep" is now a direct call into the underlying OS "sleep" function, instead
	   of being a Perl wrapper on "CORE::sleep".  "POSIX::dup2" now returns the correct value
	   on Win32 (i.e., the file descriptor).  "POSIX::SigSet" "sigsuspend" and "sigpending"
	   and "POSIX::pause" now dispatch safe signals immediately before returning to their

	   "POSIX::Termios::setattr" now defaults the third argument to "TCSANOW", instead of 0.
	   On most platforms "TCSANOW" is defined to be 0, but on some 0 is not a valid
	   parameter, which caused a call with defaults to fail.

       o   Socket has been upgraded from version 1.94 to 2.001.

	   It has new functions and constants for handling IPv6 sockets:


       o   Storable has been upgraded from version 2.27 to 2.34.

	   It no longer turns copy-on-write scalars into read-only scalars when freezing and

       o   Sys::Syslog has been upgraded from version 0.27 to 0.29.

	   This upgrade closes many outstanding bugs.

       o   Term::ANSIColor has been upgraded from version 3.00 to 3.01.

	   Only interpret an initial array reference as a list of colors, not any initial
	   reference, allowing the colored function to work properly on objects with
	   stringification defined.

       o   Term::ReadLine has been upgraded from version 1.07 to 1.09.

	   Term::ReadLine now supports any event loop, including unpublished ones and simple
	   IO::Select, loops without the need to rewrite existing code for any particular
	   framework [perl #108470].

       o   threads::shared has been upgraded from version 1.37 to 1.40.

	   Destructors on shared objects used to be ignored sometimes if the objects were
	   referenced only by shared data structures.  This has been mostly fixed, but
	   destructors may still be ignored if the objects still exist at global destruction time
	   [perl #98204].

       o   Unicode::Collate has been upgraded from version 0.73 to 0.89.

	   Updated to CLDR 1.9.1

	   Locales updated to CLDR 2.0: mk, mt, nb, nn, ro, ru, sk, sr, sv, uk, zh__pinyin,

	   Newly supported locales: bn, fa, ml, mr, or, pa, sa, si, si__dictionary, sr_Latn,
	   sv__reformed, ta, te, th, ur, wae.

	   Tailored compatibility ideographs as well as unified ideographs for the locales: ja,
	   ko, zh__big5han, zh__gb2312han, zh__pinyin, zh__stroke.

	   Locale/*.pl files are now searched for in @INC.

       o   Unicode::Normalize has been upgraded from version 1.10 to 1.14.

	   Fixes for the removal of unicore/CompositionExclusions.txt from core.

       o   Unicode::UCD has been upgraded from version 0.32 to 0.43.

	   This adds four new functions:  "prop_aliases()" and "prop_value_aliases()", which are
	   used to find all Unicode-approved synonyms for property names, or to convert from one
	   name to another; "prop_invlist" which returns all code points matching a given Unicode
	   binary property; and "prop_invmap" which returns the complete specification of a given
	   Unicode property.

       o   Win32API::File has been upgraded from version 0.1101 to 0.1200.

	   Added SetStdHandle and GetStdHandle functions

   Removed Modules and Pragmata
       As promised in Perl 5.14.0's release notes, the following modules have been removed from
       the core distribution, and if needed should be installed from CPAN instead.

       o   Devel::DProf has been removed from the Perl core.  Prior version was 20110228.00.

       o   Shell has been removed from the Perl core.  Prior version was 0.72_01.

       o   Several old perl4-style libraries which have been deprecated with 5.14 are now

	       abbrev.pl assert.pl bigfloat.pl bigint.pl bigrat.pl cacheout.pl
	       complete.pl ctime.pl dotsh.pl exceptions.pl fastcwd.pl flush.pl
	       getcwd.pl getopt.pl getopts.pl hostname.pl importenv.pl
	       lib/find{,depth}.pl look.pl newgetopt.pl open2.pl open3.pl
	       pwd.pl shellwords.pl stat.pl tainted.pl termcap.pl timelocal.pl

	   They can be found on CPAN as Perl4::CoreLibs.

   New Documentation

       perldtrace describes Perl's DTrace support, listing the provided probes and gives examples
       of their use.


       This document is intended to provide a list of experimental features in Perl.  It is still
       a work in progress.


       This a new OO tutorial.	It focuses on basic OO concepts, and then recommends that readers
       choose an OO framework from CPAN.


       The new manual describes the XS typemapping mechanism in unprecedented detail and combines
       new documentation with information extracted from perlxs and the previously unofficial
       list of all core typemaps.

   Changes to Existing Documentation

       o   The HV API has long accepted negative lengths to show that the key is in UTF8.  This
	   is now documented.

       o   The "boolSV()" macro is now documented.


       o   "dbmopen" treats a 0 mode as a special case, that prevents a nonexistent file from
	   being created.  This has been the case since Perl 5.000, but was never documented
	   anywhere.  Now the perlfunc entry mentions it [perl #90064].

       o   As an accident of history, "open $fh, '<:', ..." applies the default layers for the
	   platform (":raw" on Unix, ":crlf" on Windows), ignoring whatever is declared by
	   open.pm.  This seems such a useful feature it has been documented in perlfunc and

       o   The entry for "split" has been rewritten.  It is now far clearer than before.


       o   A new section, Autoloading with XSUBs, has been added, which explains the two APIs for
	   accessing the name of the autoloaded sub.

       o   Some function descriptions in perlguts were confusing, as it was not clear whether
	   they referred to the function above or below the description.  This has been clarified
	   [perl #91790].


       o   This document has been rewritten from scratch, and its coverage of various OO concepts
	   has been expanded.


       o   Documentation of the smartmatch operator has been reworked and moved from perlsyn to
	   perlop where it belongs.

	   It has also been corrected for the case of "undef" on the left-hand side.  The list of
	   different smart match behaviors had an item in the wrong place.

       o   Documentation of the ellipsis statement ("...") has been reworked and moved from
	   perlop to perlsyn.

       o   The explanation of bitwise operators has been expanded to explain how they work on
	   Unicode strings (5.14.1).

       o   More examples for "m//g" have been added (5.14.1).

       o   The "<<\FOO" here-doc syntax has been documented (5.14.1).


       o   There is now a standard convention for naming keys in the "%^H", documented under Key

       "Laundering and Detecting Tainted Data" in perlsec

       o   The example function for checking for taintedness contained a subtle error.	$@ needs
	   to be localized to prevent its changing this global's value outside the function.  The
	   preferred method to check for this remains "tainted" in Scalar::Util.


       o   perllol has been expanded with examples using the new "push $scalar" syntax introduced
	   in Perl 5.14.0 (5.14.1).


       o   perlmod now states explicitly that some types of explicit symbol table manipulation
	   are not supported.  This codifies what was effectively already the case [perl #78074].


       o   The tips on which formatting codes to use have been corrected and greatly expanded.

       o   There are now a couple of example one-liners for previewing POD files after they have
	   been edited.


       o   The "(*COMMIT)" directive is now listed in the right section (Verbs without an


       o   perlrun has undergone a significant clean-up.  Most notably, the -0x... form of the -0
	   flag has been clarified, and the final section on environment variables has been
	   corrected and expanded (5.14.1).


       o   The ($;) prototype syntax, which has existed for rather a long time, is now documented
	   in perlsub.	It lets a unary function have the same precedence as a list operator.


       o   The required syntax for tying handles has been documented.


       o   The documentation for $! has been corrected and clarified.  It used to state that $!
	   could be "undef", which is not the case.  It was also unclear whether system calls set
	   C's "errno" or Perl's $!  [perl #91614].

       o   Documentation for $$ has been amended with additional cautions regarding changing the
	   process ID.

       Other Changes

       o   perlxs was extended with documentation on inline typemaps.

       o   perlref has a new Circular References section explaining how circularities may not be
	   freed and how to solve that with weak references.

       o   Parts of perlapi were clarified, and Perl equivalents of some C functions have been
	   added as an additional mode of exposition.

       o   A few parts of perlre and perlrecharclass were clarified.

   Removed Documentation
       Old OO Documentation

       The old OO tutorials, perltoot, perltooc, and perlboot, have been removed.  The perlbot
       (bag of object tricks) document has been removed as well.

       Development Deltas

       The perldelta files for development releases are no longer packaged with perl.  These can
       still be found in the perl source code repository.

       The following additions or changes have been made to diagnostic output, including warnings
       and fatal error messages.  For the complete list of diagnostic messages, see perldiag.

   New Diagnostics
       New Errors

       o   Cannot set tied @DB::args

	   This error occurs when "caller" tries to set @DB::args but finds it tied.  Before this
	   error was added, it used to crash instead.

       o   Cannot tie unreifiable array

	   This error is part of a safety check that the "tie" operator does before tying a
	   special array like @_.  You should never see this message.

       o   &CORE::%s cannot be called directly

	   This occurs when a subroutine in the "CORE::" namespace is called with &foo syntax or
	   through a reference.  Some subroutines in this package cannot yet be called that way,
	   but must be called as barewords.  See "Subroutines in the "CORE" namespace", above.

       o   Source filters apply only to byte streams

	   This new error occurs when you try to activate a source filter (usually by loading a
	   source filter module) within a string passed to "eval" under the "unicode_eval"

       New Warnings

       o   defined(@array) is deprecated

	   The long-deprecated "defined(@array)" now also warns for package variables.
	   Previously it issued a warning for lexical variables only.

       o   length() used on %s

	   This new warning occurs when "length" is used on an array or hash, instead of
	   "scalar(@array)" or "scalar(keys %hash)".

       o   lvalue attribute %s already-defined subroutine

	   attributes.pm now emits this warning when the :lvalue attribute is applied to a Perl
	   subroutine that has already been defined, as doing so can have unexpected side-

       o   overload arg '%s' is invalid

	   This warning, in the "overload" category, is produced when the overload pragma is
	   given an argument it doesn't recognize, presumably a mistyped operator.

       o   $[ used in %s (did you mean $] ?)

	   This new warning exists to catch the mistaken use of $[ in version checks.  $], not
	   $[, contains the version number.

       o   Useless assignment to a temporary

	   Assigning to a temporary scalar returned from an lvalue subroutine now produces this
	   warning [perl #31946].

       o   Useless use of \E

	   "\E" does nothing unless preceded by "\Q", "\L" or "\U".

   Removed Errors
       o   "sort is now a reserved word"

	   This error used to occur when "sort" was called without arguments, followed by ";" or
	   ")".  (E.g., "sort;" would die, but "{sort}" was OK.)  This error message was added in
	   Perl 3 to catch code like "close(sort)" which would no longer work.	More than two
	   decades later, this message is no longer appropriate.  Now "sort" without arguments is
	   always allowed, and returns an empty list, as it did in those cases where it was
	   already allowed [perl #90030].

   Changes to Existing Diagnostics
       o   The "Applying pattern match..." or similar warning produced when an array or hash is
	   on the left-hand side of the "=~" operator now mentions the name of the variable.

       o   The "Attempt to free non-existent shared string" has had the spelling of "non-
	   existent" corrected to "nonexistent".  It was already listed with the correct spelling
	   in perldiag.

       o   The error messages for using "default" and "when" outside a topicalizer have been
	   standardized to match the messages for "continue" and loop controls.  They now read
	   'Can't "default" outside a topicalizer' and 'Can't "when" outside a topicalizer'.
	   They both used to be 'Can't use when() outside a topicalizer' [perl #91514].

       o   The message, "Code point 0x%X is not Unicode, no properties match it; all inverse
	   properties do" has been changed to "Code point 0x%X is not Unicode, all \p{} matches
	   fail; all \P{} matches succeed".

       o   Redefinition warnings for constant subroutines used to be mandatory, even occurring
	   under "no warnings".  Now they respect the warnings pragma.

       o   The "glob failed" warning message is now suppressible via "no warnings" [perl

       o   The Invalid version format error message now says "negative version number" within the
	   parentheses, rather than "non-numeric data", for negative numbers.

       o   The two warnings Possible attempt to put comments in qw() list and Possible attempt to
	   separate words with commas are no longer mutually exclusive: the same "qw" construct
	   may produce both.

       o   The uninitialized warning for "y///r" when $_ is implicit and undefined now mentions
	   the variable name, just like the non-/r variation of the operator.

       o   The 'Use of "foo" without parentheses is ambiguous' warning has been extended to apply
	   also to user-defined subroutines with a (;$) prototype, and not just to built-in

       o   Warnings that mention the names of lexical ("my") variables with Unicode characters in
	   them now respect the presence or absence of the ":utf8" layer on the output handle,
	   instead of outputting UTF8 regardless.  Also, the correct names are included in the
	   strings passed to $SIG{__WARN__} handlers, rather than the raw UTF8 bytes.

Utility Changes

       o   h2ph used to generate code of the form

	     unless(defined(&FOO)) {
	       sub FOO () {42;}

	   But the subroutine is a compile-time declaration, and is hence unaffected by the
	   condition.  It has now been corrected to emit a string "eval" around the subroutine
	   [perl #99368].


       o   splain no longer emits backtraces with the first line number repeated.


	       Uncaught exception from user code:
		       Cannot fwiddle the fwuddle at -e line 1.
		at -e line 1
		       main::baz() called at -e line 1
		       main::bar() called at -e line 1
		       main::foo() called at -e line 1

	   has become this:

	       Uncaught exception from user code:
		       Cannot fwiddle the fwuddle at -e line 1.
		       main::baz() called at -e line 1
		       main::bar() called at -e line 1
		       main::foo() called at -e line 1

       o   Some error messages consist of multiple lines that are listed as separate entries in
	   perldiag.  splain has been taught to find the separate entries in these cases, instead
	   of simply failing to find the message.


       o   This is a new utility, included as part of an IO::Compress::Base upgrade.

	   zipdetails displays information about the internal record structure of the zip file.
	   It is not concerned with displaying any details of the compressed data stored in the
	   zip file.

Configuration and Compilation
       o   regexp.h has been modified for compatibility with GCC's -Werror option, as used by
	   some projects that include perl's header files (5.14.1).

       o   "USE_LOCALE{,_COLLATE,_CTYPE,_NUMERIC}" have been added the output of perl -V as they
	   have affect the behavior of the interpreter binary (albeit in only a small area).

       o   The code and tests for IPC::Open2 have been moved from ext/IPC-Open2 into
	   ext/IPC-Open3, as "IPC::Open2::open2()" is implemented as a thin wrapper around
	   "IPC::Open3::_open3()", and hence is very tightly coupled to it.

       o   The magic types and magic vtables are now generated from data in a new script
	   regen/mg_vtable.pl, instead of being maintained by hand.  As different EBCDIC variants
	   can't agree on the code point for '~', the character to code point conversion is done
	   at build time by generate_uudmap to a new generated header mg_data.h.  "PL_vtbl_bm"
	   and "PL_vtbl_fm" are now defined by the pre-processor as "PL_vtbl_regexp", instead of
	   being distinct C variables.	"PL_vtbl_sig" has been removed.

       o   Building with "-DPERL_GLOBAL_STRUCT" works again.  This configuration is not generally

       o   Perl configured with MAD now correctly frees "MADPROP" structures when OPs are freed.
	   "MADPROP"s are now allocated with "PerlMemShared_malloc()"

       o   makedef.pl has been refactored.  This should have no noticeable affect on any of the
	   platforms that use it as part of their build (AIX, VMS, Win32).

       o   "useperlio" can no longer be disabled.

       o   The file global.sym is no longer needed, and has been removed.  It contained a list of
	   all exported functions, one of the files generated by regen/embed.pl from data in
	   embed.fnc and regen/opcodes.  The code has been refactored so that the only user of
	   global.sym, makedef.pl, now reads embed.fnc and regen/opcodes directly, removing the
	   need to store the list of exported functions in an intermediate file.

	   As global.sym was never installed, this change should not be visible outside the build

       o   pod/buildtoc, used by the build process to build perltoc, has been refactored and
	   simplified.	It now contains only code to build perltoc; the code to regenerate
	   Makefiles has been moved to Porting/pod_rules.pl.  It's a bug if this change has any
	   material effect on the build process.

       o   pod/roffitall is now built by pod/buildtoc, instead of being shipped with the
	   distribution.  Its list of manpages is now generated (and therefore current).  See
	   also RT #103202 for an unresolved related issue.

       o   The man page for "XS::Typemap" is no longer installed.  "XS::Typemap" is a test module
	   which is not installed, hence installing its documentation makes no sense.

       o   The -Dusesitecustomize and -Duserelocatableinc options now work together properly.

Platform Support
   Platform-Specific Notes

       o   Since version 1.7, Cygwin supports native UTF-8 paths.  If Perl is built under that
	   environment, directory and filenames will be UTF-8 encoded.

       o   Cygwin does not initialize all original Win32 environment variables.  See
	   README.cygwin for a discussion of the newly-added "Cygwin::sync_winenv()" function
	   [perl #110190] and for further links.


       o   HP-UX PA-RISC/64 now supports gcc-4.x

	   A fix to correct the socketsize now makes the test suite pass on HP-UX PA-RISC for
	   64bitall builds. (5.14.2)


       o   Remove unnecessary includes, fix miscellaneous compiler warnings and close some
	   unclosed comments on vms/vms.c.

       o   Remove sockadapt layer from the VMS build.

       o   Explicit support for VMS versions before v7.0 and DEC C versions before v6.0 has been

       o   Since Perl 5.10.1, the home-grown "stat" wrapper has been unable to distinguish
	   between a directory name containing an underscore and an otherwise-identical filename
	   containing a dot in the same position (e.g., t/test_pl as a directory and t/test.pl as
	   a file).  This problem has been corrected.

       o   The build on VMS now permits names of the resulting symbols in C code for Perl longer
	   than 31 characters.	Symbols like
	   "Perl__it_was_the_best_of_times_it_was_the_worst_of_times" can now be created freely
	   without causing the VMS linker to seize up.


       o   Numerous build and test failures on GNU/Hurd have been resolved with hints for
	   building DBM modules, detection of the library search path, and enabling of large file


       o   Perl is now built with dynamic linking on OpenVOS, the minimum supported version of
	   which is now Release 17.1.0.


       The CC workshop C++ compiler is now detected and used on systems that ship without cc.

Internal Changes
       o   The compiled representation of formats is now stored via the "mg_ptr" of their
	   "PERL_MAGIC_fm".  Previously it was stored in the string buffer, beyond "SvLEN()", the
	   regular end of the string.  "SvCOMPILED()" and "SvCOMPILED_{on,off}()" now exist
	   solely for compatibility for XS code.  The first is always 0, the other two now no-
	   ops. (5.14.1)

       o   Some global variables have been marked "const", members in the interpreter structure
	   have been re-ordered, and the opcodes have been re-ordered.	The op "OP_AELEMFAST" has
	   been split into "OP_AELEMFAST" and "OP_AELEMFAST_LEX".

       o   When empting a hash of its elements (e.g., via undef(%h), or %h=()), HvARRAY field is
	   no longer temporarily zeroed.  Any destructors called on the freed elements see the
	   remaining elements.	Thus, %h=() becomes more like "delete $h{$_} for keys %h".

       o   Boyer-Moore compiled scalars are now PVMGs, and the Boyer-Moore tables are now stored
	   via the mg_ptr of their "PERL_MAGIC_bm".  Previously they were PVGVs, with the tables
	   stored in the string buffer, beyond "SvLEN()".  This eliminates the last place where
	   the core stores data beyond "SvLEN()".

       o   Simplified logic in "Perl_sv_magic()" introduces a small change of behavior for error
	   cases involving unknown magic types.  Previously, if "Perl_sv_magic()" was passed a
	   magic type unknown to it, it would

	   1.  Croak "Modification of a read-only value attempted" if read only

	   2.  Return without error if the SV happened to already have this magic

	   3.  otherwise croak "Don't know how to handle magic of type \\%o"

	   Now it will always croak "Don't know how to handle magic of type \\%o", even on read-
	   only values, or SVs which already have the unknown magic type.

       o   The experimental "fetch_cop_label" function has been renamed to "cop_fetch_label".

       o   The "cop_store_label" function has been added to the API, but is experimental.

       o   embedvar.h has been simplified, and one level of macro indirection for PL_* variables
	   has been removed for the default (non-multiplicity) configuration.  PERLVAR*() macros
	   now directly expand their arguments to tokens such as "PL_defgv", instead of expanding
	   to "PL_Idefgv", with embedvar.h defining a macro to map "PL_Idefgv" to "PL_defgv".  XS
	   code which has unwarranted chumminess with the implementation may need updating.

       o   An API has been added to explicitly choose whether to export XSUB symbols.  More
	   detail can be found in the comments for commit e64345f8.

       o   The "is_gv_magical_sv" function has been eliminated and merged with
	   "gv_fetchpvn_flags".  It used to be called to determine whether a GV should be
	   autovivified in rvalue context.  Now it has been replaced with a new "GV_ADDMG" flag
	   (not part of the API).

       o   The returned code point from the function "utf8n_to_uvuni()" when the input is
	   malformed UTF-8, malformations are allowed, and "utf8" warnings are off is now the
	   Unicode REPLACEMENT CHARACTER whenever the malformation is such that no well-defined
	   code point can be computed.	Previously the returned value was essentially garbage.
	   The only malformations that have well-defined values are a zero-length string (0 is
	   the return), and overlong UTF-8 sequences.

       o   Padlists are now marked "AvREAL"; i.e., reference-counted.  They have always been
	   reference-counted, but were not marked real, because pad.c did its own clean-up,
	   instead of using the usual clean-up code in sv.c.  That caused problems in thread
	   cloning, so now the "AvREAL" flag is on, but is turned off in pad.c right before the
	   padlist is freed (after pad.c has done its custom freeing of the pads).

       o   All C files that make up the Perl core have been converted to UTF-8.

       o   These new functions have been added as part of the work on Unicode symbols:


	   The gv_fetchmethod_*_flags functions, like gv_fetchmethod_flags, are experimental and
	   may change in a future release.

       o   The following functions were added.	These are not part of the API:


	   There is also a "HEKf" macro corresponding to "SVf", for interpolating HEKs in
	   formatted strings.

       o   "sv_catpvn_flags" takes a couple of new internal-only flags, "SV_CATBYTES" and
	   "SV_CATUTF8", which tell it whether the char array to be concatenated is UTF8.  This
	   allows for more efficient concatenation than creating temporary SVs to pass to

       o   For XS AUTOLOAD subs, $AUTOLOAD is set once more, as it was in 5.6.0.  This is in
	   addition to setting "SvPVX(cv)", for compatibility with 5.8 to 5.14.  See "Autoloading
	   with XSUBs" in perlguts.

       o   Perl now checks whether the array (the linearized isa) returned by a MRO plugin begins
	   with the name of the class itself, for which the array was created, instead of
	   assuming that it does.  This prevents the first element from being skipped during
	   method lookup.  It also means that "mro::get_linear_isa" may return an array with one
	   more element than the MRO plugin provided [perl #94306].

       o   "PL_curstash" is now reference-counted.

       o   There are now feature bundle hints in "PL_hints" ($^H) that version declarations use,
	   to avoid having to load feature.pm.	One setting of the hint bits indicates a "custom"
	   feature bundle, which means that the entries in "%^H" still apply.  feature.pm uses

	   The "HINT_FEATURE_MASK" macro is defined in perl.h along with other hints.  Other
	   macros for setting and testing features and bundles are in the new feature.h.
	   "FEATURE_IS_ENABLED" (which has moved to feature.h) is no longer used throughout the
	   codebase, but more specific macros, e.g., "FEATURE_SAY_IS_ENABLED", that are defined
	   in feature.h.

       o   lib/feature.pm is now a generated file, created by the new regen/feature.pl script,
	   which also generates feature.h.

       o   Tied arrays are now always "AvREAL".  If @_ or "DB::args" is tied, it is reified
	   first, to make sure this is always the case.

       o   Two new functions "utf8_to_uvchr_buf()" and "utf8_to_uvuni_buf()" have been added.
	   These are the same as "utf8_to_uvchr" and "utf8_to_uvuni" (which are now deprecated),
	   but take an extra parameter that is used to guard against reading beyond the end of
	   the input string.  See "utf8_to_uvchr_buf" in perlapi and "utf8_to_uvuni_buf" in

       o   The regular expression engine now does TRIE case insensitive matches under Unicode.
	   This may change the output of "use re 'debug';", and will speed up various things.

       o   There is a new "wrap_op_checker()" function, which provides a thread-safe alternative
	   to writing to "PL_check" directly.

Selected Bug Fixes
   Array and hash
       o   A bug has been fixed that would cause a "Use of freed value in iteration" error if the
	   next two hash elements that would be iterated over are deleted [perl #85026]. (5.14.1)

       o   Deleting the current hash iterator (the hash element that would be returned by the
	   next call to "each") in void context used not to free it [perl #85026].

       o   Deletion of methods via "delete $Class::{method}" syntax used to update method caches
	   if called in void context, but not scalar or list context.

       o   When hash elements are deleted in void context, the internal hash entry is now freed
	   before the value is freed, to prevent destructors called by that latter freeing from
	   seeing the hash in an inconsistent state.  It was possible to cause double-frees if
	   the destructor freed the hash itself [perl #100340].

       o   A "keys" optimization in Perl 5.12.0 to make it faster on empty hashes caused "each"
	   not to reset the iterator if called after the last element was deleted.

       o   Freeing deeply nested hashes no longer crashes [perl #44225].

       o   It is possible from XS code to create hashes with elements that have no values.  The
	   hash element and slice operators used to crash when handling these in lvalue context.
	   They now produce a "Modification of non-creatable hash value attempted" error message.

       o   If list assignment to a hash or array triggered destructors that freed the hash or
	   array itself, a crash would ensue.  This is no longer the case [perl #107440].

       o   It used to be possible to free the typeglob of a localized array or hash (e.g., "local
	   @{"x"}; delete $::{x}"), resulting in a crash on scope exit.

       o   Some core bugs affecting Hash::Util have been fixed: locking a hash element that is a
	   glob copy no longer causes the next assignment to it to corrupt the glob (5.14.2), and
	   unlocking a hash element that holds a copy-on-write scalar no longer causes
	   modifications to that scalar to modify other scalars that were sharing the same string

   C API fixes
       o   The "newHVhv" XS function now works on tied hashes, instead of crashing or returning
	   an empty hash.

       o   The "SvIsCOW" C macro now returns false for read-only copies of typeglobs, such as
	   those created by:

	     $hash{elem} = *foo;
	     Hash::Util::lock_value %hash, 'elem';

	   It used to return true.

       o   The "SvPVutf8" C function no longer tries to modify its argument, resulting in errors
	   [perl #108994].

       o   "SvPVutf8" now works properly with magical variables.

       o   "SvPVbyte" now works properly non-PVs.

       o   When presented with malformed UTF-8 input, the XS-callable functions
	   "is_utf8_string()", "is_utf8_string_loc()", and "is_utf8_string_loclen()" could read
	   beyond the end of the input string by up to 12 bytes.  This no longer happens.  [perl
	   #32080].  However, currently, "is_utf8_char()" still has this defect, see
	   "is_utf8_char()" above.

       o   The C-level "pregcomp" function could become confused about whether the pattern was in
	   UTF8 if the pattern was an overloaded, tied, or otherwise magical scalar [perl

   Compile-time hints
       o   Tying "%^H" no longer causes perl to crash or ignore the contents of "%^H" when
	   entering a compilation scope [perl #106282].

       o   "eval $string" and "require" used not to localize "%^H" during compilation if it was
	   empty at the time the "eval" call itself was compiled.  This could lead to scary side
	   effects, like "use re "/m"" enabling other flags that the surrounding code was trying
	   to enable for its caller [perl #68750].

       o   "eval $string" and "require" no longer localize hints ($^H and "%^H") at run time, but
	   only during compilation of the $string or required file.  This makes "BEGIN {
	   $^H{foo}=7 }" equivalent to "BEGIN { eval '$^H{foo}=7' }" [perl #70151].

       o   Creating a BEGIN block from XS code (via "newXS" or "newATTRSUB") would, on
	   completion, make the hints of the current compiling code the current hints.	This
	   could cause warnings to occur in a non-warning scope.

   Copy-on-write scalars
       Copy-on-write or shared hash key scalars were introduced in 5.8.0, but most Perl code did
       not encounter them (they were used mostly internally).  Perl 5.10.0 extended them, such
       that assigning "__PACKAGE__" or a hash key to a scalar would make it copy-on-write.
       Several parts of Perl were not updated to account for them, but have now been fixed.

       o   "utf8::decode" had a nasty bug that would modify copy-on-write scalars' string buffers
	   in place (i.e., skipping the copy).	This could result in hashes having two elements
	   with the same key [perl #91834]. (5.14.2)

       o   Lvalue subroutines were not allowing COW scalars to be returned.  This was fixed for
	   lvalue scalar context in Perl 5.12.3 and 5.14.0, but list context was not fixed until
	   this release.

       o   Elements of restricted hashes (see the fields pragma) containing copy-on-write values
	   couldn't be deleted, nor could such hashes be cleared ("%hash = ()"). (5.14.2)

       o   Localizing a tied variable used to make it read-only if it contained a copy-on-write
	   string. (5.14.2)

       o   Assigning a copy-on-write string to a stash element no longer causes a double free.
	   Regardless of this change, the results of such assignments are still undefined.

       o   Assigning a copy-on-write string to a tied variable no longer stops that variable from
	   being tied if it happens to be a PVMG or PVLV internally.

       o   Doing a substitution on a tied variable returning a copy-on-write scalar used to cause
	   an assertion failure or an "Attempt to free nonexistent shared string" warning.

       o   This one is a regression from 5.12: In 5.14.0, the bitwise assignment operators "|=",
	   "^=" and "&=" started leaving the left-hand side undefined if it happened to be a
	   copy-on-write string [perl #108480].

       o   Storable, Devel::Peek and PerlIO::scalar had similar problems.  See "Updated Modules
	   and Pragmata", above.

   The debugger
       o   dumpvar.pl, and therefore the "x" command in the debugger, have been fixed to handle
	   objects blessed into classes whose names contain "=".  The contents of such objects
	   used not to be dumped [perl #101814].

       o   The "R" command for restarting a debugger session has been fixed to work on Windows,
	   or any other system lacking a "POSIX::_SC_OPEN_MAX" constant [perl #87740].

       o   The "#line 42 foo" directive used not to update the arrays of lines used by the
	   debugger if it occurred in a string eval.  This was partially fixed in 5.14, but it
	   worked only for a single "#line 42 foo" in each eval.  Now it works for multiple.

       o   When subroutine calls are intercepted by the debugger, the name of the subroutine or a
	   reference to it is stored in $DB::sub, for the debugger to access.  Sometimes (such as
	   "$foo = *bar; undef *bar; &$foo") $DB::sub would be set to a name that could not be
	   used to find the subroutine, and so the debugger's attempt to call it would fail.  Now
	   the check to see whether a reference is needed is more robust, so those problems
	   should not happen anymore [rt.cpan.org #69862].

       o   Every subroutine has a filename associated with it that the debugger uses.  The one
	   associated with constant subroutines used to be misallocated when cloned under
	   threads.  Consequently, debugging threaded applications could result in memory
	   corruption [perl #96126].

   Dereferencing operators
       o   "defined(${"..."})", "defined(*{"..."})", etc., used to return true for most, but not
	   all built-in variables, if they had not been used yet.  This bug affected
	   "${^GLOBAL_PHASE}" and "${^UTF8CACHE}", among others.  It also used to return false if
	   the package name was given as well ("${"::!"}") [perl #97978, #97492].

       o   Perl 5.10.0 introduced a similar bug: "defined(*{"foo"})" where "foo" represents the
	   name of a built-in global variable used to return false if the variable had never been
	   used before, but only on the first call.  This, too, has been fixed.

       o   Since 5.6.0, "*{ ... }" has been inconsistent in how it treats undefined values.  It
	   would die in strict mode or lvalue context for most undefined values, but would be
	   treated as the empty string (with a warning) for the specific scalar return by
	   "undef()" (&PL_sv_undef internally).  This has been corrected.  "undef()" is now
	   treated like other undefined scalars, as in Perl 5.005.

   Filehandle, last-accessed
       Perl has an internal variable that stores the last filehandle to be accessed.  It is used
       by $. and by "tell" and "eof" without arguments.

       o   It used to be possible to set this internal variable to a glob copy and then modify
	   that glob copy to be something other than a glob, and still have the last-accessed
	   filehandle associated with the variable after assigning a glob to it again:

	       my $foo = *STDOUT;  # $foo is a glob copy
	       <$foo>;		   # $foo is now the last-accessed handle
	       $foo = 3;	   # no longer a glob
	       $foo = *STDERR;	   # still the last-accessed handle

	   Now the "$foo = 3" assignment unsets that internal variable, so there is no last-
	   accessed filehandle, just as if "<$foo>" had never happened.

	   This also prevents some unrelated handle from becoming the last-accessed handle if
	   $foo falls out of scope and the same internal SV gets used for another handle [perl

       o   A regression in 5.14 caused these statements not to set that internal variable:

	       my $fh = *STDOUT;
	       tell $fh;
	       eof  $fh;
	       seek $fh, 0,0;
	       tell	*$fh;
	       eof	*$fh;
	       seek	*$fh, 0,0;
	       readline *$fh;

	   This is now fixed, but "tell *{ *$fh }" still has the problem, and it is not clear how
	   to fix it [perl #106536].

   Filetests and "stat"
       The term "filetests" refers to the operators that consist of a hyphen followed by a single
       letter: "-r", "-x", "-M", etc.  The term "stacked" when applied to filetests means
       followed by another filetest operator sharing the same operand, as in "-r -x -w $fooo".

       o   "stat" produces more consistent warnings.  It no longer warns for "_" [perl #71002]
	   and no longer skips the warning at times for other unopened handles.  It no longer
	   warns about an unopened handle when the operating system's "fstat" function fails.

       o   "stat" would sometimes return negative numbers for large inode numbers, because it was
	   using the wrong internal C type. [perl #84590]

       o   "lstat" is documented to fall back to "stat" (with a warning) when given a filehandle.
	   When passed an IO reference, it was actually doing the equivalent of "stat _" and
	   ignoring the handle.

       o   "-T _" with no preceding "stat" used to produce a confusing "uninitialized" warning,
	   even though there is no visible uninitialized value to speak of.

       o   "-T", "-B", "-l" and "-t" now work when stacked with other filetest operators [perl

       o   In 5.14.0, filetest ops ("-r", "-x", etc.) started calling FETCH on a tied argument
	   belonging to the previous argument to a list operator, if called with a bareword
	   argument or no argument at all.  This has been fixed, so "push @foo, $tied, -r" no
	   longer calls FETCH on $tied.

       o   In Perl 5.6, "-l" followed by anything other than a bareword would treat its argument
	   as a file name.  That was changed in 5.8 for glob references ("\*foo"), but not for
	   globs themselves (*foo).  "-l" started returning "undef" for glob references without
	   setting the last stat buffer that the "_" handle uses, but only if warnings were
	   turned on.  With warnings off, it was the same as 5.6.  In other words, it was simply
	   buggy and inconsistent.  Now the 5.6 behavior has been restored.

       o   "-l" followed by a bareword no longer "eats" the previous argument to the list
	   operator in whose argument list it resides.	Hence, "print "bar", -l foo" now actually
	   prints "bar", because "-l" on longer eats it.

       o   Perl keeps several internal variables to keep track of the last stat buffer, from
	   which file(handle) it originated, what type it was, and whether the last stat

	   There were various cases where these could get out of synch, resulting in inconsistent
	   or erratic behavior in edge cases (every mention of "-T" applies to "-B" as well):

	   o   "-T HANDLE", even though it does a "stat", was not resetting the last stat type,
	       so an "lstat _" following it would merrily return the wrong results.  Also, it was
	       not setting the success status.

	   o   Freeing the handle last used by "stat" or a filetest could result in "-T _" using
	       an unrelated handle.

	   o   "stat" with an IO reference would not reset the stat type or record the filehandle
	       for "-T _" to use.

	   o   Fatal warnings could cause the stat buffer not to be reset for a filetest operator
	       on an unopened filehandle or "-l" on any handle.  Fatal warnings also stopped "-T"
	       from setting $!.

	   o   When the last stat was on an unreadable file, "-T _" is supposed to return
	       "undef", leaving the last stat buffer unchanged.  But it was setting the stat
	       type, causing "lstat _" to stop working.

	   o   "-T FILENAME" was not resetting the internal stat buffers for unreadable files.

	   These have all been fixed.

       o   Several edge cases have been fixed with formats and "formline"; in particular, where
	   the format itself is potentially variable (such as with ties and overloading), and
	   where the format and data differ in their encoding.	In both these cases, it used to
	   possible for the output to be corrupted [perl #91032].

       o   "formline" no longer converts its argument into a string in-place.  So passing a
	   reference to "formline" no longer destroys the reference [perl #79532].

       o   Assignment to $^A (the format output accumulator) now recalculates the number of lines

   "given" and "when"
       o   "given" was not scoping its implicit $_ properly, resulting in memory leaks or
	   "Variable is not available" warnings [perl #94682].

       o   "given" was not calling set-magic on the implicit lexical $_ that it uses.  This
	   meant, for example, that "pos" would be remembered from one execution of the same
	   "given" block to the next, even if the input were a different variable [perl #84526].

       o   "when" blocks are now capable of returning variables declared inside the enclosing
	   "given" block [perl #93548].

   The "glob" operator
       o   On OSes other than VMS, Perl's "glob" operator (and the "<...>" form) use File::Glob
	   underneath.	File::Glob splits the pattern into words, before feeding each word to its
	   "bsd_glob" function.

	   There were several inconsistencies in the way the split was done.  Now quotation marks
	   (' and ") are always treated as shell-style word delimiters (that allow whitespace as
	   part of a word) and backslashes are always preserved, unless they exist to escape
	   quotation marks.  Before, those would only sometimes be the case, depending on whether
	   the pattern contained whitespace.  Also, escaped whitespace at the end of the pattern
	   is no longer stripped [perl #40470].

       o   "CORE::glob" now works as a way to call the default globbing function.  It used to
	   respect overrides, despite the "CORE::" prefix.

       o   Under miniperl (used to configure modules when perl itself is built), "glob" now
	   clears %ENV before calling csh, since the latter croaks on some systems if it does not
	   like the contents of the LS_COLORS environment variable [perl #98662].

   Lvalue subroutines
       o   Explicit return now returns the actual argument passed to return, instead of copying
	   it [perl #72724, #72706].

       o   Lvalue subroutines used to enforce lvalue syntax (i.e., whatever can go on the left-
	   hand side of "=") for the last statement and the arguments to return.  Since lvalue
	   subroutines are not always called in lvalue context, this restriction has been lifted.

       o   Lvalue subroutines are less restrictive about what values can be returned.  It used to
	   croak on values returned by "shift" and "delete" and from other subroutines, but no
	   longer does so [perl #71172].

       o   Empty lvalue subroutines ("sub :lvalue {}") used to return @_ in list context.  All
	   subroutines used to do this, but regular subs were fixed in Perl 5.8.2.  Now lvalue
	   subroutines have been likewise fixed.

       o   Autovivification now works on values returned from lvalue subroutines [perl #7946], as
	   does returning "keys" in lvalue context.

       o   Lvalue subroutines used to copy their return values in rvalue context.  Not only was
	   this a waste of CPU cycles, but it also caused bugs.  A "($)" prototype would cause an
	   lvalue sub to copy its return value [perl #51408], and "while(lvalue_sub() =~ m/.../g)
	   { ... }" would loop endlessly [perl #78680].

       o   When called in potential lvalue context (e.g., subroutine arguments or a list passed
	   to "for"), lvalue subroutines used to copy any read-only value that was returned.
	   E.g., " sub :lvalue { $] } " would not return $], but a copy of it.

       o   When called in potential lvalue context, an lvalue subroutine returning arrays or
	   hashes used to bind the arrays or hashes to scalar variables, resulting in bugs.  This
	   was fixed in 5.14.0 if an array were the first thing returned from the subroutine (but
	   not for "$scalar, @array" or hashes being returned).  Now a more general fix has been
	   applied [perl #23790].

       o   Method calls whose arguments were all surrounded with "my()" or "our()" (as in
	   "$object->method(my($a,$b))") used to force lvalue context on the subroutine.  This
	   would prevent lvalue methods from returning certain values.

       o   Lvalue sub calls that are not determined to be such at compile time (&$name or
	   &{"name"}) are no longer exempt from strict refs if they occur in the last statement
	   of an lvalue subroutine [perl #102486].

       o   Sub calls whose subs are not visible at compile time, if they occurred in the last
	   statement of an lvalue subroutine, would reject non-lvalue subroutines and die with
	   "Can't modify non-lvalue subroutine call" [perl #102486].

	   Non-lvalue sub calls whose subs are visible at compile time exhibited the opposite
	   bug.  If the call occurred in the last statement of an lvalue subroutine, there would
	   be no error when the lvalue sub was called in lvalue context.  Perl would blindly
	   assign to the temporary value returned by the non-lvalue subroutine.

       o   "AUTOLOAD" routines used to take precedence over the actual sub being called (i.e.,
	   when autoloading wasn't needed), for sub calls in lvalue or potential lvalue context,
	   if the subroutine was not visible at compile time.

       o   Applying the ":lvalue" attribute to an XSUB or to an aliased subroutine stub with "sub
	   foo :lvalue;" syntax stopped working in Perl 5.12.  This has been fixed.

       o   Applying the :lvalue attribute to subroutine that is already defined does not work
	   properly, as the attribute changes the way the sub is compiled.  Hence, Perl 5.12
	   began warning when an attempt is made to apply the attribute to an already defined
	   sub.  In such cases, the attribute is discarded.

	   But the change in 5.12 missed the case where custom attributes are also present: that
	   case still silently and ineffectively applied the attribute.  That omission has now
	   been corrected.  "sub foo :lvalue :Whatever" (when "foo" is already defined) now warns
	   about the :lvalue attribute, and does not apply it.

       o   A bug affecting lvalue context propagation through nested lvalue subroutine calls has
	   been fixed.	Previously, returning a value in nested rvalue context would be treated
	   as lvalue context by the inner subroutine call, resulting in some values (such as
	   read-only values) being rejected.

       o   Arithmetic assignment ("$left += $right") involving overloaded objects that rely on
	   the 'nomethod' override no longer segfault when the left operand is not overloaded.

       o   Errors that occur when methods cannot be found during overloading now mention the
	   correct package name, as they did in 5.8.x, instead of erroneously mentioning the
	   "overload" package, as they have since 5.10.0.

       o   Undefining %overload:: no longer causes a crash.

   Prototypes of built-in keywords
       o   The "prototype" function no longer dies for the "__FILE__", "__LINE__" and
	   "__PACKAGE__" directives.  It now returns an empty-string prototype for them, because
	   they are syntactically indistinguishable from nullary functions like "time".

       o   "prototype" now returns "undef" for all overridable infix operators, such as "eq",
	   which are not callable in any way resembling functions.  It used to return incorrect
	   prototypes for some and die for others [perl #94984].

       o   The prototypes of several built-in functions--"getprotobynumber", "lock", "not" and
	   "select"--have been corrected, or at least are now closer to reality than before.

   Regular expressions
       o   "/[[:ascii:]]/" and "/[[:blank:]]/" now use locale rules under "use locale" when the
	   platform supports that.  Previously, they used the platform's native character set.

       o   "m/[[:ascii:]]/i" and "/\p{ASCII}/i" now match identically (when not under a differing
	   locale).  This fixes a regression introduced in 5.14 in which the first expression
	   could match characters outside of ASCII, such as the KELVIN SIGN.

       o   "/.*/g" would sometimes refuse to match at the end of a string that ends with "\n".
	   This has been fixed [perl #109206].

       o   Starting with 5.12.0, Perl used to get its internal bookkeeping muddled up after
	   assigning "${ qr// }" to a hash element and locking it with Hash::Util.  This could
	   result in double frees, crashes, or erratic behavior.

       o   The new (in 5.14.0) regular expression modifier "/a" when repeated like "/aa" forbids
	   the characters outside the ASCII range that match characters inside that range from
	   matching under "/i".  This did not work under some circumstances, all involving
	   alternation, such as:

	    "\N{KELVIN SIGN}" =~ /k|foo/iaa;

	   succeeded inappropriately.  This is now fixed.

       o   5.14.0 introduced some memory leaks in regular expression character classes such as
	   "[\w\s]", which have now been fixed. (5.14.1)

       o   An edge case in regular expression matching could potentially loop.	This happened
	   only under "/i" in bracketed character classes that have characters with multi-
	   character folds, and the target string to match against includes the first portion of
	   the fold, followed by another character that has a multi-character fold that begins
	   with the remaining portion of the fold, plus some more.

	    "s\N{U+DF}" =~ /[\x{DF}foo]/i

	   is one such case.  "\xDF" folds to "ss". (5.14.1)

       o   A few characters in regular expression pattern matches did not match correctly in some
	   circumstances, all involving "/i".  The affected characters are: COMBINING GREEK

       o   A memory leak regression in regular expression compilation under threading has been

       o   A regression introduced in 5.14.0 has been fixed.  This involved an inverted bracketed
	   character class in a regular expression that consisted solely of a Unicode property.
	   That property wasn't getting inverted outside the Latin1 range.

       o   Three problematic Unicode characters now work better in regex pattern matching under

	   In the past, three Unicode characters: LATIN SMALL LETTER SHARP S, GREEK SMALL LETTER
	   TONOS, along with the sequences that they fold to (including "ss" for LATIN SMALL
	   LETTER SHARP S), did not properly match under "/i".	5.14.0 fixed some of these cases,
	   but introduced others, including a panic when one of the characters or sequences was
	   used in the "(?(DEFINE)" regular expression predicate.  The known bugs that were
	   introduced in 5.14 have now been fixed; as well as some other edge cases that have
	   never worked until now.  These all involve using the characters and sequences outside
	   bracketed character classes under "/i".  This closes [perl #98546].

	   There remain known problems when using certain characters with multi-character folds
	   inside bracketed character classes, including such constructs as "qr/[\N{LATIN SMALL
	   LETTER SHARP}a-z]/i".  These remaining bugs are addressed in [perl #89774].

       o   RT #78266: The regex engine has been leaking memory when accessing named captures that
	   weren't matched as part of a regex ever since 5.10 when they were introduced; e.g.,
	   this would consume over a hundred MB of memory:

	       for (1..10_000_000) {
		   if ("foo" =~ /(foo|(?<capture>bar))?/) {
		       my $capture = $+{capture}
	       system "ps -o rss $$"'

       o   In 5.14, "/[[:lower:]]/i" and "/[[:upper:]]/i" no longer matched the opposite case.
	   This has been fixed [perl #101970].

       o   A regular expression match with an overloaded object on the right-hand side would
	   sometimes stringify the object too many times.

       o   A regression has been fixed that was introduced in 5.14, in "/i" regular expression
	   matching, in which a match improperly fails if the pattern is in UTF-8, the target
	   string is not, and a Latin-1 character precedes a character in the string that should
	   match the pattern.  [perl #101710]

       o   In case-insensitive regular expression pattern matching, no longer on UTF-8 encoded
	   strings does the scan for the start of match look only at the first possible position.
	   This caused matches such as ""f\x{FB00}" =~ /ff/i" to fail.

       o   The regexp optimizer no longer crashes on debugging builds when merging fixed-string
	   nodes with inconvenient contents.

       o   A panic involving the combination of the regular expression modifiers "/aa" and the
	   "\b" escape sequence introduced in 5.14.0 has been fixed [perl #95964]. (5.14.2)

       o   The combination of the regular expression modifiers "/aa" and the "\b" and "\B" escape
	   sequences did not work properly on UTF-8 encoded strings.  All non-ASCII characters
	   under "/aa" should be treated as non-word characters, but what was happening was that
	   Unicode rules were used to determine wordness/non-wordness for non-ASCII characters.
	   This is now fixed [perl #95968].

       o   "(?foo: ...)" no longer loses passed in character set.

       o   The trie optimization used to have problems with alternations containing an empty
	   "(?:)", causing ""x" =~ /\A(?>(?:(?:)A|B|C?x))\z/" not to match, whereas it should
	   [perl #111842].

       o   Use of lexical ("my") variables in code blocks embedded in regular expressions will no
	   longer result in memory corruption or crashes.

	   Nevertheless, these code blocks are still experimental, as there are still problems
	   with the wrong variables being closed over (in loops for instance) and with abnormal
	   exiting (e.g., "die") causing memory corruption.

       o   The "\h", "\H", "\v" and "\V" regular expression metacharacters used to cause a panic
	   error message when trying to match at the end of the string [perl #96354].

       o   The abbreviations for four C1 control characters "MW" "PM", "RI", and "ST" were
	   previously unrecognized by "\N{}", vianame(), and string_vianame().

       o   Mentioning a variable named "&" other than $& (i.e., "@&" or "%&") no longer stops $&
	   from working.  The same applies to variables named "'" and "`" [perl #24237].

       o   Creating a "UNIVERSAL::AUTOLOAD" sub no longer stops "%+", "%-" and "%!" from working
	   some of the time [perl #105024].

       o   "~~" now correctly handles the precedence of Any~~Object, and is not tricked by an
	   overloaded object on the left-hand side.

       o   In Perl 5.14.0, "$tainted ~~ @array" stopped working properly.  Sometimes it would
	   erroneously fail (when $tainted contained a string that occurs in the array after the
	   first element) or erroneously succeed (when "undef" occurred after the first element)
	   [perl #93590].

   The "sort" operator
       o   "sort" was not treating "sub {}" and "sub {()}" as equivalent when such a sub was
	   provided as the comparison routine.	It used to croak on "sub {()}".

       o   "sort" now works once more with custom sort routines that are XSUBs.  It stopped
	   working in 5.10.0.

       o   "sort" with a constant for a custom sort routine, although it produces unsorted
	   results, no longer crashes.	It started crashing in 5.10.0.

       o   Warnings emitted by "sort" when a custom comparison routine returns a non-numeric
	   value now contain "in sort" and show the line number of the "sort" operator, rather
	   than the last line of the comparison routine.  The warnings also now occur only if
	   warnings are enabled in the scope where "sort" occurs.  Previously the warnings would
	   occur if enabled in the comparison routine's scope.

       o   "sort { $a <=> $b }", which is optimized internally, now produces "uninitialized"
	   warnings for NaNs (not-a-number values), since "<=>" returns "undef" for those.  This
	   brings it in line with "sort { 1; $a <=> $b }" and other more complex cases, which are
	   not optimized [perl #94390].

   The "substr" operator
       o   Tied (and otherwise magical) variables are no longer exempt from the "Attempt to use
	   reference as lvalue in substr" warning.

       o   That warning now occurs when the returned lvalue is assigned to, not when "substr"
	   itself is called.  This makes a difference only if the return value of "substr" is
	   referenced and later assigned to.

       o   Passing a substring of a read-only value or a typeglob to a function (potential lvalue
	   context) no longer causes an immediate "Can't coerce" or "Modification of a read-only
	   value" error.  That error occurs only if the passed value is assigned to.

	   The same thing happens with the "substr outside of string" error.  If the lvalue is
	   only read from, not written to, it is now just a warning, as with rvalue "substr".

       o   "substr" assignments no longer call FETCH twice if the first argument is a tied
	   variable, just once.

   Support for embedded nulls
       Some parts of Perl did not work correctly with nulls ("chr 0") embedded in strings.  That
       meant that, for instance, "$m = "a\0b"; foo->$m" would call the "a" method, instead of the
       actual method name contained in $m.  These parts of perl have been fixed to support nulls:

       o   Method names

       o   Typeglob names (including filehandle and subroutine names)

       o   Package names, including the return value of "ref()"

       o   Typeglob elements (*foo{"THING\0stuff"})

       o   Signal names

       o   Various warnings and error messages that mention variable names or values, methods,

       One side effect of these changes is that blessing into "\0" no longer causes "ref()" to
       return false.

   Threading bugs
       o   Typeglobs returned from threads are no longer cloned if the parent thread already has
	   a glob with the same name.  This means that returned subroutines will now assign to
	   the right package variables [perl #107366].

       o   Some cases of threads crashing due to memory allocation during cloning have been fixed
	   [perl #90006].

       o   Thread joining would sometimes emit "Attempt to free unreferenced scalar" warnings if
	   "caller" had been used from the "DB" package before thread creation [perl #98092].

       o   Locking a subroutine (via "lock &sub") is no longer a compile-time error for regular
	   subs.  For lvalue subroutines, it no longer tries to return the sub as a scalar,
	   resulting in strange side effects like "ref \$_" returning "CODE" in some instances.

	   "lock &sub" is now a run-time error if threads::shared is loaded (a no-op otherwise),
	   but that may be rectified in a future version.

   Tied variables
       o   Various cases in which FETCH was being ignored or called too many times have been

	   o   "PerlIO::get_layers" [perl #97956]

	   o   "$tied =~ y/a/b/", "chop $tied" and "chomp $tied" when $tied holds a reference.

	   o   When calling "local $_" [perl #105912]

	   o   Four-argument "select"

	   o   A tied buffer passed to "sysread"

	   o   "$tied .= <>"

	   o   Three-argument "open", the third being a tied file handle (as in "open $fh, ">&",

	   o   "sort" with a reference to a tied glob for the comparison routine.

	   o   ".." and "..." in list context [perl #53554].

	   o   "${$tied}", "@{$tied}", "%{$tied}" and "*{$tied}" where the tied variable returns
	       a string ("&{}" was unaffected)

	   o   "defined ${ $tied_variable }"

	   o   Various functions that take a filehandle argument in rvalue context ("close",
	       "readline", etc.) [perl #97482]

	   o   Some cases of dereferencing a complex expression, such as "${ (), $tied } = 1",
	       used to call "FETCH" multiple times, but now call it once.

	   o   "$tied->method" where $tied returns a package name--even resulting in a failure to
	       call the method, due to memory corruption

	   o   Assignments like "*$tied = \&{"..."}" and "*glob = $tied"

	   o   "chdir", "chmod", "chown", "utime", "truncate", "stat", "lstat" and the filetest
	       ops ("-r", "-x", etc.)

       o   "caller" sets @DB::args to the subroutine arguments when called from the DB package.
	   It used to crash when doing so if @DB::args happened to be tied.  Now it croaks

       o   Tying an element of %ENV or "%^H" and then deleting that element would result in a
	   call to the tie object's DELETE method, even though tying the element itself is
	   supposed to be equivalent to tying a scalar (the element is, of course, a scalar)
	   [perl #67490].

       o   When Perl autovivifies an element of a tied array or hash (which entails calling STORE
	   with a new reference), it now calls FETCH immediately after the STORE, instead of
	   assuming that FETCH would have returned the same reference.	This can make it easier
	   to implement tied objects [perl #35865, #43011].

       o   Four-argument "select" no longer produces its "Non-string passed as bitmask" warning
	   on tied or tainted variables that are strings.

       o   Localizing a tied scalar that returns a typeglob no longer stops it from being tied
	   till the end of the scope.

       o   Attempting to "goto" out of a tied handle method used to cause memory corruption or
	   crashes.  Now it produces an error message instead [perl #8611].

       o   A bug has been fixed that occurs when a tied variable is used as a subroutine
	   reference:  if the last thing assigned to or returned from the variable was a
	   reference or typeglob, the "\&$tied" could either crash or return the wrong
	   subroutine.	The reference case is a regression introduced in Perl 5.10.0.  For
	   typeglobs, it has probably never worked till now.

   Version objects and vstrings
       o   The bitwise complement operator (and possibly other operators, too) when passed a
	   vstring would leave vstring magic attached to the return value, even though the string
	   had changed.  This meant that "version->new(~v1.2.3)" would create a version looking
	   like "v1.2.3" even though the string passed to "version->new" was actually
	   "\376\375\374".  This also caused B::Deparse to deparse "~v1.2.3" incorrectly, without
	   the "~" [perl #29070].

       o   Assigning a vstring to a magic (e.g., tied, $!) variable and then assigning something
	   else used to blow away all magic.  This meant that tied variables would come undone,
	   $! would stop getting updated on failed system calls, $| would stop setting autoflush,
	   and other mischief would take place.  This has been fixed.

       o   "version->new("version")" and "printf "%vd", "version"" no longer crash [perl

       o   Version comparisons, such as those that happen implicitly with "use v5.43", no longer
	   cause locale settings to change [perl #105784].

       o   Version objects no longer cause memory leaks in boolean context [perl #109762].

   Warnings, redefinition
       o   Subroutines from the "autouse" namespace are once more exempt from redefinition
	   warnings.  This used to work in 5.005, but was broken in 5.6 for most subroutines.
	   For subs created via XS that redefine subroutines from the "autouse" package, this
	   stopped working in 5.10.

       o   New XSUBs now produce redefinition warnings if they overwrite existing subs, as they
	   did in 5.8.x.  (The "autouse" logic was reversed in 5.10-14.  Only subroutines from
	   the "autouse" namespace would warn when clobbered.)

       o   "newCONSTSUB" used to use compile-time warning hints, instead of run-time hints.  The
	   following code should never produce a redefinition warning, but it used to, if
	   "newCONSTSUB" redefined an existing subroutine:

	       use warnings;
	       BEGIN {
		   no warnings;

       o   Redefinition warnings for constant subroutines are on by default (what are known as
	   severe warnings in perldiag).  This occurred only when it was a glob assignment or
	   declaration of a Perl subroutine that caused the warning.  If the creation of XSUBs
	   triggered the warning, it was not a default warning.  This has been corrected.

       o   The internal check to see whether a redefinition warning should occur used to emit
	   "uninitialized" warnings in cases like this:

	       use warnings "uninitialized";
	       use constant {u => undef, v => undef};
	       sub foo(){u}
	       sub foo(){v}

   Warnings, "Uninitialized"
       o   Various functions that take a filehandle argument in rvalue context ("close",
	   "readline", etc.) used to warn twice for an undefined handle [perl #97482].

       o   "dbmopen" now only warns once, rather than three times, if the mode argument is
	   "undef" [perl #90064].

       o   The "+=" operator does not usually warn when the left-hand side is "undef", but it was
	   doing so for tied variables.  This has been fixed [perl #44895].

       o   A bug fix in Perl 5.14 introduced a new bug, causing "uninitialized" warnings to
	   report the wrong variable if the operator in question had two operands and one was
	   "%{...}" or "@{...}".  This has been fixed [perl #103766].

       o   ".." and "..." in list context now mention the name of the variable in "uninitialized"
	   warnings for string (as opposed to numeric) ranges.

   Weak references
       o   Weakening the first argument to an automatically-invoked "DESTROY" method could result
	   in erroneous "DESTROY created new reference" errors or crashes.  Now it is an error to
	   weaken a read-only reference.

       o   Weak references to lexical hashes going out of scope were not going stale (becoming
	   undefined), but continued to point to the hash.

       o   Weak references to lexical variables going out of scope are now broken before any
	   magical methods (e.g., DESTROY on a tie object) are called.	This prevents such
	   methods from modifying the variable that will be seen the next time the scope is

       o   Creating a weak reference to an @ISA array or accessing the array index ($#ISA) could
	   result in confused internal bookkeeping for elements later added to the @ISA array.
	   For instance, creating a weak reference to the element itself could push that weak
	   reference on to @ISA; and elements added after use of $#ISA would be ignored by method
	   lookup [perl #85670].

   Other notable fixes
       o   "quotemeta" now quotes consistently the same non-ASCII characters under "use feature
	   'unicode_strings'", regardless of whether the string is encoded in UTF-8 or not, hence
	   fixing the last vestiges (we hope) of the notorious "The "Unicode Bug"" in
	   perlunicode.  [perl #77654].

	   Which of these code points is quoted has changed, based on Unicode's recommendations.
	   See "quotemeta" in perlfunc for details.

       o   "study" is now a no-op, presumably fixing all outstanding bugs related to study
	   causing regex matches to behave incorrectly!

       o   When one writes "open foo || die", which used to work in Perl 4, a "Precedence
	   problem" warning is produced.  This warning used erroneously to apply to fully-
	   qualified bareword handle names not followed by "||".  This has been corrected.

       o   After package aliasing ("*foo:: = *bar::"), "select" with 0 or 1 argument would
	   sometimes return a name that could not be used to refer to the filehandle, or
	   sometimes it would return "undef" even when a filehandle was selected.  Now it returns
	   a typeglob reference in such cases.

       o   "PerlIO::get_layers" no longer ignores some arguments that it thinks are numeric,
	   while treating others as filehandle names.  It is now consistent for flat scalars
	   (i.e., not references).

       o   Unrecognized switches on "#!" line

	   If a switch, such as -x, that cannot occur on the "#!" line is used there, perl dies
	   with "Can't emulate...".

	   It used to produce the same message for switches that perl did not recognize at all,
	   whether on the command line or the "#!" line.

	   Now it produces the "Unrecognized switch" error message [perl #104288].

       o   "system" now temporarily blocks the SIGCHLD signal handler, to prevent the signal
	   handler from stealing the exit status [perl #105700].

       o   The %n formatting code for "printf" and "sprintf", which causes the number of
	   characters to be assigned to the next argument, now actually assigns the number of
	   characters, instead of the number of bytes.

	   It also works now with special lvalue functions like "substr" and with nonexistent
	   hash and array elements [perl #3471, #103492].

       o   Perl skips copying values returned from a subroutine, for the sake of speed, if doing
	   so would make no observable difference.  Because of faulty logic, this would happen
	   with the result of "delete", "shift" or "splice", even if the result was referenced
	   elsewhere.  It also did so with tied variables about to be freed [perl #91844,

       o   "utf8::decode" now refuses to modify read-only scalars [perl #91850].

       o   Freeing $_ inside a "grep" or "map" block, a code block embedded in a regular
	   expression, or an @INC filter (a subroutine returned by a subroutine in @INC) used to
	   result in double frees or crashes [perl #91880, #92254, #92256].

       o   "eval" returns "undef" in scalar context or an empty list in list context when there
	   is a run-time error.  When "eval" was passed a string in list context and a syntax
	   error occurred, it used to return a list containing a single undefined element.  Now
	   it returns an empty list in list context for all errors [perl #80630].

       o   "goto &func" no longer crashes, but produces an error message, when the unwinding of
	   the current subroutine's scope fires a destructor that undefines the subroutine being
	   "goneto" [perl #99850].

       o   Perl now holds an extra reference count on the package that code is currently
	   compiling in.  This means that the following code no longer crashes [perl #101486]:

	       package Foo;
	       BEGIN {*Foo:: = *Bar::}
	       sub foo;

       o   The "x" repetition operator no longer crashes on 64-bit builds with large repeat
	   counts [perl #94560].

       o   Calling "require" on an implicit $_ when *CORE::GLOBAL::require has been overridden
	   does not segfault anymore, and $_ is now passed to the overriding subroutine [perl

       o   "use" and "require" are no longer affected by the I/O layers active in the caller's
	   scope (enabled by open.pm) [perl #96008].

       o   "our $::e; $e" (which is invalid) no longer produces the "Compilation error at
	   lib/utf8_heavy.pl..." error message, which it started emitting in 5.10.0 [perl

       o   On 64-bit systems, "read()" now understands large string offsets beyond the 32-bit

       o   Errors that occur when processing subroutine attributes no longer cause the
	   subroutine's op tree to leak.

       o   Passing the same constant subroutine to both "index" and "formline" no longer causes
	   one or the other to fail [perl #89218]. (5.14.1)

       o   List assignment to lexical variables declared with attributes in the same statement
	   ("my ($x,@y) : blimp = (72,94)") stopped working in Perl 5.8.0.  It has now been

       o   Perl 5.10.0 introduced some faulty logic that made "U*" in the middle of a pack
	   template equivalent to "U0" if the input string was empty.  This has been fixed [perl
	   #90160]. (5.14.2)

       o   Destructors on objects were not called during global destruction on objects that were
	   not referenced by any scalars.  This could happen if an array element were blessed
	   (e.g., "bless \$a[0]") or if a closure referenced a blessed variable ("bless \my @a;
	   sub foo { @a }").

	   Now there is an extra pass during global destruction to fire destructors on any
	   objects that might be left after the usual passes that check for objects referenced by
	   scalars [perl #36347].

       o   Fixed a case where it was possible that a freed buffer may have been read from when
	   parsing a here document [perl #90128]. (5.14.1)

       o   "each(ARRAY)" is now wrapped in "defined(...)", like "each(HASH)", inside a "while"
	   condition [perl #90888].

       o   A problem with context propagation when a "do" block is an argument to "return" has
	   been fixed.	It used to cause "undef" to be returned in certain cases of a "return"
	   inside an "if" block which itself is followed by another "return".

       o   Calling "index" with a tainted constant no longer causes constants in subsequently
	   compiled code to become tainted [perl #64804].

       o   Infinite loops like "1 while 1" used to stop "strict 'subs'" mode from working for the
	   rest of the block.

       o   For list assignments like "($a,$b) = ($b,$a)", Perl has to make a copy of the items on
	   the right-hand side before assignment them to the left.  For efficiency's sake, it
	   assigns the values on the right straight to the items on the left if no one variable
	   is mentioned on both sides, as in "($a,$b) = ($c,$d)".  The logic for determining when
	   it can cheat was faulty, in that "&&" and "||" on the right-hand side could fool it.
	   So "($a,$b) = $some_true_value && ($b,$a)" would end up assigning the value of $b to
	   both scalars.

       o   Perl no longer tries to apply lvalue context to the string in "("string", $variable)
	   ||= 1" (which used to be an error).	Since the left-hand side of "||=" is evaluated in
	   scalar context, that's a scalar comma operator, which gives all but the last item void
	   context.  There is no such thing as void lvalue context, so it was a mistake for Perl
	   to try to force it [perl #96942].

       o   "caller" no longer leaks memory when called from the DB package if @DB::args was
	   assigned to after the first call to "caller".  Carp was triggering this bug [perl
	   #97010]. (5.14.2)

       o   "close" and similar filehandle functions, when called on built-in global variables
	   (like $+), used to die if the variable happened to hold the undefined value, instead
	   of producing the usual "Use of uninitialized value" warning.

       o   When autovivified file handles were introduced in Perl 5.6.0, "readline" was
	   inadvertently made to autovivify when called as "readline($foo)" (but not as
	   "<$foo>").  It has now been fixed never to autovivify.

       o   Calling an undefined anonymous subroutine (e.g., what $x holds after "undef &{$x =
	   sub{}}") used to cause a "Not a CODE reference" error, which has been corrected to
	   "Undefined subroutine called" [perl #71154].

       o   Causing @DB::args to be freed between uses of "caller" no longer results in a crash
	   [perl #93320].

       o   "setpgrp($foo)" used to be equivalent to "($foo, setpgrp)", because "setpgrp" was
	   ignoring its argument if there was just one.  Now it is equivalent to

       o   "shmread" was not setting the scalar flags correctly when reading from shared memory,
	   causing the existing cached numeric representation in the scalar to persist [perl

       o   "++" and "--" now work on copies of globs, instead of dying.

       o   "splice()" doesn't warn when truncating

	   You can now limit the size of an array using "splice(@a,MAX_LEN)" without worrying
	   about warnings.

       o   $$ is no longer tainted.  Since this value comes directly from "getpid()", it is
	   always safe.

       o   The parser no longer leaks a filehandle if STDIN was closed before parsing started
	   [perl #37033].

       o   "die;" with a non-reference, non-string, or magical (e.g., tainted) value in $@ now
	   properly propagates that value [perl #111654].

Known Problems
       o   On Solaris, we have two kinds of failure.

	   If make is Sun's make, we get an error about a badly formed macro assignment in the
	   Makefile.  That happens when ./Configure tries to make depends.  Configure then exits
	   0, but further make-ing fails.

	   If make is gmake, Configure completes, then we get errors related to

       o   On Win32, a number of tests hang unless STDERR is redirected.  The cause of this is
	   still under investigation.

       o   When building as root with a umask that prevents files from being other-readable,
	   t/op/filetest.t will fail.  This is a test bug, not a bug in perl's behavior.

       o   Configuring with a recent gcc and link-time-optimization, such as "Configure
	   -Doptimize='-O2 -flto'" fails because the optimizer optimizes away some of Configure's
	   tests.  A workaround is to omit the "-flto" flag when running Configure, but add it
	   back in while actually building, something like

	       sh Configure -Doptimize=-O2
	       make OPTIMIZE='-O2 -flto'

       o   The following CPAN modules have test failures with perl 5.16.  Patches have been
	   submitted for all of these, so hopefully there will be new releases soon:

	   o   Date::Pcalc version 6.1

	   o   Module::CPANTS::Analyse version 0.85

	       This fails due to problems in Module::Find 0.10 and File::MMagic 1.27.

	   o   PerlIO::Util version 0.72

       Perl 5.16.0 represents approximately 12 months of development since Perl 5.14.0 and
       contains approximately 590,000 lines of changes across 2,500 files from 139 authors.

       Perl continues to flourish into its third decade thanks to a vibrant community of users
       and developers.	The following people are known to have contributed the improvements that
       became Perl 5.16.0:

       Aaron Crane, Abhijit Menon-Sen, Abigail, Alan Haggai Alavi, Alberto Simo~es, Alexandr
       Ciornii, Andreas Koenig, Andy Dougherty, Aristotle Pagaltzis, Bo Johansson, Bo Lindbergh,
       Breno G. de Oliveira, brian d foy, Brian Fraser, Brian Greenfield, Carl Hayter, Chas.
       Owens, Chia-liang Kao, Chip Salzenberg, Chris 'BinGOs' Williams, Christian Hansen,
       Christopher J. Madsen, chromatic, Claes Jacobsson, Claudio Ramirez, Craig A. Berry, Damian
       Conway, Daniel Kahn Gillmor, Darin McBride, Dave Rolsky, David Cantrell, David Golden,
       David Leadbeater, David Mitchell, Dee Newcum, Dennis Kaarsemaker, Dominic Hargreaves,
       Douglas Christopher Wilson, Eric Brine, Father Chrysostomos, Florian Ragwitz, Frederic
       Briere, George Greer, Gerard Goossen, Gisle Aas, H.Merijn Brand, Hojung Youn, Ian
       Goodacre, James E Keenan, Jan Dubois, Jerry D. Hedden, Jesse Luehrs, Jesse Vincent, Jilles
       Tjoelker, Jim Cromie, Jim Meyering, Joel Berger, Johan Vromans, Johannes Plunien, John
       Hawkinson, John P. Linderman, John Peacock, Joshua ben Jore, Juerd Waalboer, Karl
       Williamson, Karthik Rajagopalan, Keith Thompson, Kevin J.  Woolley, Kevin Ryde, Laurent
       Dami, Leo Lapworth, Leon Brocard, Leon Timmermans, Louis Strous, Lukas Mai, Marc Green,
       Marcel Gruenauer, Mark A.  Stratman, Mark Dootson, Mark Jason Dominus, Martin Hasch,
       Matthew Horsfall, Max Maischein, Michael G Schwern, Michael Witten, Mike Sheldrake, Moritz
       Lenz, Nicholas Clark, Niko Tyni, Nuno Carvalho, Pau Amma, Paul Evans, Paul Green, Paul
       Johnson, Perlover, Peter John Acklam, Peter Martini, Peter Scott, Phil Monsen, Pino
       Toscano, Rafael Garcia-Suarez, Rainer Tammer, Reini Urban, Ricardo Signes, Robin Barker,
       Rodolfo Carvalho, Salvador Fandin~o, Sam Kimbrel, Samuel Thibault, Shawn M Moore, Shigeya
       Suzuki, Shirakata Kentaro, Shlomi Fish, Sisyphus, Slaven Rezic, Spiros Denaxas, Steffen
       Mueller, Steffen Schwigon, Stephen Bennett, Stephen Oberholtzer, Stevan Little, Steve Hay,
       Steve Peters, Thomas Sibley, Thorsten Glaser, Timothe Litt, Todd Rinaldo, Tom
       Christiansen, Tom Hukins, Tony Cook, Vadim Konovalov, Vincent Pit, Vladimir Timofeev, Walt
       Mankowski, Yves Orton, Zefram, Zsban Ambrus, var Arnfjoer` Bjarmason.

       The list above is almost certainly incomplete as it is automatically generated from
       version control history.  In particular, it does not include the names of the (very much
       appreciated) contributors who reported issues to the Perl bug tracker.

       Many of the changes included in this version originated in the CPAN modules included in
       Perl's core.  We're grateful to the entire CPAN community for helping Perl to flourish.

       For a more complete list of all of Perl's historical contributors, please see the AUTHORS
       file in the Perl source distribution.

Reporting Bugs
       If you find what you think is a bug, you might check the articles recently posted to the
       comp.lang.perl.misc newsgroup and the perl bug database at <http://rt.perl.org/perlbug/>.
       There may also be information at <http://www.perl.org/>, the Perl Home Page.

       If you believe you have an unreported bug, please run the perlbug program included with
       your release.  Be sure to trim your bug down to a tiny but sufficient test case.  Your bug
       report, along with the output of "perl -V", will be sent off to perlbug@perl.org to be
       analysed by the Perl porting team.

       If the bug you are reporting has security implications, which make it inappropriate to
       send to a publicly archived mailing list, then please send it to
       perl5-security-report@perl.org.	This points to a closed subscription unarchived mailing
       list, which includes all core committers, who will be able to help assess the impact of
       issues, figure out a resolution, and help co-ordinate the release of patches to mitigate
       or fix the problem across all platforms on which Perl is supported.  Please use this
       address only for security issues in the Perl core, not for modules independently
       distributed on CPAN.

       The Changes file for an explanation of how to view exhaustive details on what changed.

       The INSTALL file for how to build Perl.

       The README file for general stuff.

       The Artistic and Copying files for copyright information.

perl v5.16.3				    2013-03-04				 PERL5160DELTA(1)
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