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PERL5120DELTA(1)		 Perl Programmers Reference Guide		 PERL5120DELTA(1)

NAME
       perl5120delta - what is new for perl v5.12.0

DESCRIPTION
       This document describes differences between the 5.10.0 release and the 5.12.0 release.

       Many of the bug fixes in 5.12.0 are already included in the 5.10.1 maintenance release.

       You can see the list of those changes in the 5.10.1 release notes (perl5101delta).

Core Enhancements
   New "package NAME VERSION" syntax
       This new syntax allows a module author to set the $VERSION of a namespace when the
       namespace is declared with 'package'. It eliminates the need for "our $VERSION = ..." and
       similar constructs. E.g.

	     package Foo::Bar 1.23;
	     # $Foo::Bar::VERSION == 1.23

       There are several advantages to this:

       o   $VERSION is parsed in exactly the same way as "use NAME VERSION"

       o   $VERSION is set at compile time

       o   $VERSION is a version object that provides proper overloading of comparison operators
	   so comparing $VERSION to decimal (1.23) or dotted-decimal (v1.2.3) version numbers
	   works correctly.

       o   Eliminates "$VERSION = ..." and "eval $VERSION" clutter

       o   As it requires VERSION to be a numeric literal or v-string literal, it can be
	   statically parsed by toolchain modules without "eval" the way MM->parse_version does
	   for "$VERSION = ..."

       It does not break old code with only "package NAME", but code that uses "package NAME
       VERSION" will need to be restricted to perl 5.12.0 or newer This is analogous to the
       change to "open" from two-args to three-args.  Users requiring the latest Perl will
       benefit, and perhaps after several years, it will become a standard practice.

       However, "package NAME VERSION" requires a new, 'strict' version number format. See
       "Version number formats" for details.

   The "..." operator
       A new operator, "...", nicknamed the Yada Yada operator, has been added.  It is intended
       to mark placeholder code that is not yet implemented.  See "Yada Yada Operator" in perlop.

   Implicit strictures
       Using the "use VERSION" syntax with a version number greater or equal to 5.11.0 will
       lexically enable strictures just like "use strict" would do (in addition to enabling
       features.) The following:

	   use 5.12.0;

       means:

	   use strict;
	   use feature ':5.12';

   Unicode improvements
       Perl 5.12 comes with Unicode 5.2, the latest version available to us at the time of
       release.  This version of Unicode was released in October 2009. See
       <http://www.unicode.org/versions/Unicode5.2.0> for further details about what's changed in
       this version of the standard.  See perlunicode for instructions on installing and using
       other versions of Unicode.

       Additionally, Perl's developers have significantly improved Perl's Unicode implementation.
       For full details, see "Unicode overhaul" below.

   Y2038 compliance
       Perl's core time-related functions are now Y2038 compliant. (It may not mean much to you,
       but your kids will love it!)

   qr overloading
       It is now possible to overload the "qr//" operator, that is, conversion to regexp, like it
       was already possible to overload conversion to boolean, string or number of objects. It is
       invoked when an object appears on the right hand side of the "=~" operator or when it is
       interpolated into a regexp. See overload.

   Pluggable keywords
       Extension modules can now cleanly hook into the Perl parser to define new kinds of
       keyword-headed expression and compound statement. The syntax following the keyword is
       defined entirely by the extension. This allow a completely non-Perl sublanguage to be
       parsed inline, with the correct ops cleanly generated.

       See "PL_keyword_plugin" in perlapi for the mechanism. The Perl core source distribution
       also includes a new module XS::APItest::KeywordRPN, which implements reverse Polish
       notation arithmetic via pluggable keywords. This module is mainly used for test purposes,
       and is not normally installed, but also serves as an example of how to use the new
       mechanism.

       Perl's developers consider this feature to be experimental. We may remove it or change it
       in a backwards-incompatible way in Perl 5.14.

   APIs for more internals
       The lowest layers of the lexer and parts of the pad system now have C APIs available to XS
       extensions. These are necessary to support proper use of pluggable keywords, but have
       other uses too. The new APIs are experimental, and only cover a small proportion of what
       would be necessary to take full advantage of the core's facilities in these areas. It is
       intended that the Perl 5.13 development cycle will see the addition of a full range of
       clean, supported interfaces.

       Perl's developers consider this feature to be experimental. We may remove it or change it
       in a backwards-incompatible way in Perl 5.14.

   Overridable function lookup
       Where an extension module hooks the creation of rv2cv ops to modify the subroutine lookup
       process, this now works correctly for bareword subroutine calls. This means that
       prototypes on subroutines referenced this way will be processed correctly. (Previously
       bareword subroutine names were initially looked up, for parsing purposes, by an unhookable
       mechanism, so extensions could only properly influence subroutine names that appeared with
       an "&" sigil.)

   A proper interface for pluggable Method Resolution Orders
       As of Perl 5.12.0 there is a new interface for plugging and using method resolution orders
       other than the default linear depth first search.  The C3 method resolution order added in
       5.10.0 has been re-implemented as a plugin, without changing its Perl-space interface. See
       perlmroapi for more information.

   "\N" experimental regex escape
       Perl now supports "\N", a new regex escape which you can think of as the inverse of "\n".
       It will match any character that is not a newline, independently from the presence or
       absence of the single line match modifier "/s". It is not usable within a character class.
       "\N{3}" means to match 3 non-newlines; "\N{5,}" means to match at least 5.  "\N{NAME}"
       still means the character or sequence named "NAME", but "NAME" no longer can be things
       like 3, or "5,".

       This will break a custom charnames translator which allows numbers for character names, as
       "\N{3}" will now mean to match 3 non-newline characters, and not the character whose name
       is 3. (No name defined by the Unicode standard is a number, so only custom translators
       might be affected.)

       Perl's developers are somewhat concerned about possible user confusion with the existing
       "\N{...}" construct which matches characters by their Unicode name. Consequently, this
       feature is experimental. We may remove it or change it in a backwards-incompatible way in
       Perl 5.14.

   DTrace support
       Perl now has some support for DTrace. See "DTrace support" in INSTALL.

   Support for "configure_requires" in CPAN module metadata
       Both "CPAN" and "CPANPLUS" now support the "configure_requires" keyword in the META.yml
       metadata file included in most recent CPAN distributions.  This allows distribution
       authors to specify configuration prerequisites that must be installed before running
       Makefile.PL or Build.PL.

       See the documentation for "ExtUtils::MakeMaker" or "Module::Build" for more on how to
       specify "configure_requires" when creating a distribution for CPAN.

   "each", "keys", "values" are now more flexible
       The "each", "keys", "values" function can now operate on arrays.

   "when" as a statement modifier
       "when" is now allowed to be used as a statement modifier.

   $, flexibility
       The variable $, may now be tied.

   // in when clauses
       // now behaves like || in when clauses

   Enabling warnings from your shell environment
       You can now set "-W" from the "PERL5OPT" environment variable

   "delete local"
       "delete local" now allows you to locally delete a hash entry.

   New support for Abstract namespace sockets
       Abstract namespace sockets are Linux-specific socket type that live in AF_UNIX family,
       slightly abusing it to be able to use arbitrary character arrays as addresses: They start
       with nul byte and are not terminated by nul byte, but with the length passed to the
       socket() system call.

   32-bit limit on substr arguments removed
       The 32-bit limit on "substr" arguments has now been removed. The full range of the
       system's signed and unsigned integers is now available for the "pos" and "len" arguments.

Potentially Incompatible Changes
   Deprecations warn by default
       Over the years, Perl's developers have deprecated a number of language features for a
       variety of reasons.  Perl now defaults to issuing a warning if a deprecated language
       feature is used. Many of the deprecations Perl now warns you about have been deprecated
       for many years.	You can find a list of what was deprecated in a given release of Perl in
       the "perl5xxdelta.pod" file for that release.

       To disable this feature in a given lexical scope, you should use "no warnings
       'deprecated';" For information about which language features are deprecated and
       explanations of various deprecation warnings, please see perldiag. See "Deprecations"
       below for the list of features and modules Perl's developers have deprecated as part of
       this release.

   Version number formats
       Acceptable version number formats have been formalized into "strict" and "lax" rules.
       "package NAME VERSION" takes a strict version number.  "UNIVERSAL::VERSION" and the
       version object constructors take lax version numbers. Providing an invalid version will
       result in a fatal error. The version argument in "use NAME VERSION" is first parsed as a
       numeric literal or v-string and then passed to "UNIVERSAL::VERSION" (and must then pass
       the "lax" format test).

       These formats are documented fully in the version module. To a first approximation, a
       "strict" version number is a positive decimal number (integer or decimal-fraction) without
       exponentiation or else a dotted-decimal v-string with a leading 'v' character and at least
       three components. A "lax" version number allows v-strings with fewer than three components
       or without a leading 'v'. Under "lax" rules, both decimal and dotted-decimal versions may
       have a trailing "alpha" component separated by an underscore character after a fractional
       or dotted-decimal component.

       The version module adds "version::is_strict" and "version::is_lax" functions to check a
       scalar against these rules.

   @INC reorganization
       In @INC, "ARCHLIB" and "PRIVLIB" now occur after after the current version's "site_perl"
       and "vendor_perl".  Modules installed into "site_perl" and "vendor_perl" will now be
       loaded in preference to those installed in "ARCHLIB" and "PRIVLIB".

   REGEXPs are now first class
       Internally, Perl now treats compiled regular expressions (such as those created with
       "qr//") as first class entities. Perl modules which serialize, deserialize or otherwise
       have deep interaction with Perl's internal data structures need to be updated for this
       change.	Most affected CPAN modules have already been updated as of this writing.

   Switch statement changes
       The "given"/"when" switch statement handles complex statements better than Perl 5.10.0 did
       (These enhancements are also available in 5.10.1 and subsequent 5.10 releases.) There are
       two new cases where "when" now interprets its argument as a boolean, instead of an
       expression to be used in a smart match:

       flip-flop operators
	   The ".." and "..." flip-flop operators are now evaluated in boolean context, following
	   their usual semantics; see "Range Operators" in perlop.

	   Note that, as in perl 5.10.0, "when (1..10)" will not work to test whether a given
	   value is an integer between 1 and 10; you should use "when ([1..10])" instead (note
	   the array reference).

	   However, contrary to 5.10.0, evaluating the flip-flop operators in boolean context
	   ensures it can now be useful in a "when()", notably for implementing bistable
	   conditions, like in:

	       when (/^=begin/ .. /^=end/) {
		 # do something
	       }

       defined-or operator
	   A compound expression involving the defined-or operator, as in "when (expr1 //
	   expr2)", will be treated as boolean if the first expression is boolean. (This just
	   extends the existing rule that applies to the regular or operator, as in "when (expr1
	   || expr2)".)

   Smart match changes
       Since Perl 5.10.0, Perl's developers have made a number of changes to the smart match
       operator. These, of course, also alter the behaviour of the switch statements where smart
       matching is implicitly used.  These changes were also made for the 5.10.1 release, and
       will remain in subsequent 5.10 releases.

       Changes to type-based dispatch

       The smart match operator "~~" is no longer commutative. The behaviour of a smart match now
       depends primarily on the type of its right hand argument. Moreover, its semantics have
       been adjusted for greater consistency or usefulness in several cases. While the general
       backwards compatibility is maintained, several changes must be noted:

       o   Code references with an empty prototype are no longer treated specially.  They are
	   passed an argument like the other code references (even if they choose to ignore it).

       o   "%hash ~~ sub {}" and "@array ~~ sub {}" now test that the subroutine returns a true
	   value for each key of the hash (or element of the array), instead of passing the whole
	   hash or array as a reference to the subroutine.

       o   Due to the commutativity breakage, code references are no longer treated specially
	   when appearing on the left of the "~~" operator, but like any vulgar scalar.

       o   "undef ~~ %hash" is always false (since "undef" can't be a key in a hash). No implicit
	   conversion to "" is done (as was the case in perl 5.10.0).

       o   "$scalar ~~ @array" now always distributes the smart match across the elements of the
	   array. It's true if one element in @array verifies "$scalar ~~ $element". This is a
	   generalization of the old behaviour that tested whether the array contained the
	   scalar.

       The full dispatch table for the smart match operator is given in "Smart matching in
       detail" in perlsyn.

       Smart match and overloading

       According to the rule of dispatch based on the rightmost argument type, when an object
       overloading "~~" appears on the right side of the operator, the overload routine will
       always be called (with a 3rd argument set to a true value, see overload.) However, when
       the object will appear on the left, the overload routine will be called only when the
       rightmost argument is a simple scalar. This way, distributivity of smart match across
       arrays is not broken, as well as the other behaviours with complex types (coderefs,
       hashes, regexes). Thus, writers of overloading routines for smart match mostly need to
       worry only with comparing against a scalar, and possibly with stringification overloading;
       the other common cases will be automatically handled consistently.

       "~~" will now refuse to work on objects that do not overload it (in order to avoid relying
       on the object's underlying structure). (However, if the object overloads the
       stringification or the numification operators, and if overload fallback is active, it will
       be used instead, as usual.)

   Other potentially incompatible changes
       o   The definitions of a number of Unicode properties have changed to match those of the
	   current Unicode standard. These are listed above under "Unicode overhaul". This change
	   may break code that expects the old definitions.

       o   The boolkeys op has moved to the group of hash ops. This breaks binary compatibility.

       o   Filehandles are now always blessed into "IO::File".

	   The previous behaviour was to bless Filehandles into FileHandle (an empty proxy class)
	   if it was loaded into memory and otherwise to bless them into "IO::Handle".

       o   The semantics of "use feature :5.10*" have changed slightly.  See "Modules and
	   Pragmata" for more information.

       o   Perl's developers now use git, rather than Perforce.  This should be a purely internal
	   change only relevant to people actively working on the core.  However, you may see
	   minor difference in perl as a consequence of the change.  For example in some of
	   details of the output of "perl -V". See perlrepository for more information.

       o   As part of the "Test::Harness" 2.x to 3.x upgrade, the experimental
	   "Test::Harness::Straps" module has been removed.  See "Modules and Pragmata" for more
	   details.

       o   As part of the "ExtUtils::MakeMaker" upgrade, the "ExtUtils::MakeMaker::bytes" and
	   "ExtUtils::MakeMaker::vmsish" modules have been removed from this distribution.

       o   "Module::CoreList" no longer contains the %:patchlevel hash.

       o   "length undef" now returns undef.

       o   Unsupported private C API functions are now declared "static" to prevent leakage to
	   Perl's public API.

       o   To support the bootstrapping process, miniperl no longer builds with UTF-8 support in
	   the regexp engine.

	   This allows a build to complete with PERL_UNICODE set and a UTF-8 locale.  Without
	   this there's a bootstrapping problem, as miniperl can't load the UTF-8 components of
	   the regexp engine, because they're not yet built.

       o   miniperl's @INC is now restricted to just "-I...", the split of $ENV{PERL5LIB}, and
	   "".""

       o   A space or a newline is now required after a "#line XXX" directive.

       o   Tied filehandles now have an additional method EOF which provides the EOF type.

       o   To better match all other flow control statements, "foreach" may no longer be used as
	   an attribute.

       o   Perl's command-line switch "-P", which was deprecated in version 5.10.0, has now been
	   removed. The CPAN module "Filter::cpp" can be used as an alternative.

Deprecations
       From time to time, Perl's developers find it necessary to deprecate features or modules
       we've previously shipped as part of the core distribution. We are well aware of the pain
       and frustration that a backwards-incompatible change to Perl can cause for developers
       building or maintaining software in Perl. You can be sure that when we deprecate a
       functionality or syntax, it isn't a choice we make lightly. Sometimes, we choose to
       deprecate functionality or syntax because it was found to be poorly designed or
       implemented. Sometimes, this is because they're holding back other features or causing
       performance problems. Sometimes, the reasons are more complex. Wherever possible, we try
       to keep deprecated functionality available to developers in its previous form for at least
       one major release. So long as a deprecated feature isn't actively disrupting our ability
       to maintain and extend Perl, we'll try to leave it in place as long as possible.

       The following items are now deprecated:

       suidperl
	   "suidperl" is no longer part of Perl. It used to provide a mechanism to emulate setuid
	   permission bits on systems that don't support it properly.

       Use of ":=" to mean an empty attribute list
	   An accident of Perl's parser meant that these constructions were all equivalent:

	       my $pi := 4;
	       my $pi : = 4;
	       my $pi :  = 4;

	   with the ":" being treated as the start of an attribute list, which ends before the
	   "=". As whitespace is not significant here, all are parsed as an empty attribute list,
	   hence all the above are equivalent to, and better written as

	       my $pi = 4;

	   because no attribute processing is done for an empty list.

	   As is, this meant that ":=" cannot be used as a new token, without silently changing
	   the meaning of existing code. Hence that particular form is now deprecated, and will
	   become a syntax error. If it is absolutely necessary to have empty attribute lists
	   (for example, because of a code generator) then avoid the warning by adding a space
	   before the "=".

       "UNIVERSAL->import()"
	   The method "UNIVERSAL->import()" is now deprecated. Attempting to pass import
	   arguments to a "use UNIVERSAL" statement will result in a deprecation warning.

       Use of "goto" to jump into a construct
	   Using "goto" to jump from an outer scope into an inner scope is now deprecated. This
	   rare use case was causing problems in the implementation of scopes.

       Custom character names in \N{name} that don't look like names
	   In "\N{name}", name can be just about anything. The standard Unicode names have a very
	   limited domain, but a custom name translator could create names that are, for example,
	   made up entirely of punctuation symbols. It is now deprecated to make names that don't
	   begin with an alphabetic character, and aren't alphanumeric or contain other than a
	   very few other characters, namely spaces, dashes, parentheses and colons. Because of
	   the added meaning of "\N" (See ""\N" experimental regex escape"), names that look like
	   curly brace -enclosed quantifiers won't work. For example, "\N{3,4}" now means to
	   match 3 to 4 non-newlines; before a custom name "3,4" could have been created.

       Deprecated Modules
	   The following modules will be removed from the core distribution in a future release,
	   and should be installed from CPAN instead. Distributions on CPAN which require these
	   should add them to their prerequisites. The core versions of these modules warnings
	   will issue a deprecation warning.

	   If you ship a packaged version of Perl, either alone or as part of a larger system,
	   then you should carefully consider the repercussions of core module deprecations. You
	   may want to consider shipping your default build of Perl with packages for some or all
	   deprecated modules which install into "vendor" or "site" perl library directories.
	   This will inhibit the deprecation warnings.

	   Alternatively, you may want to consider patching lib/deprecate.pm to provide
	   deprecation warnings specific to your packaging system or distribution of Perl,
	   consistent with how your packaging system or distribution manages a staged transition
	   from a release where the installation of a single package provides the given
	   functionality, to a later release where the system administrator needs to know to
	   install multiple packages to get that same functionality.

	   You can silence these deprecation warnings by installing the modules in question from
	   CPAN.  To install the latest version of all of them, just install
	   "Task::Deprecations::5_12".

	   Class::ISA
	   Pod::Plainer
	   Shell
	   Switch
	       Switch is buggy and should be avoided. You may find Perl's new "given"/"when"
	       feature a suitable replacement.	See "Switch statements" in perlsyn for more
	       information.

       Assignment to $[
       Use of the attribute :locked on subroutines
       Use of "locked" with the attributes pragma
       Use of "unique" with the attributes pragma
       Perl_pmflag
	   "Perl_pmflag" is no longer part of Perl's public API. Calling it now generates a
	   deprecation warning, and it will be removed in a future release. Although listed as
	   part of the API, it was never documented, and only ever used in toke.c, and prior to
	   5.10, regcomp.c. In core, it has been replaced by a static function.

       Numerous Perl 4-era libraries
	   termcap.pl, tainted.pl, stat.pl, shellwords.pl, pwd.pl, open3.pl, open2.pl,
	   newgetopt.pl, look.pl, find.pl, finddepth.pl, importenv.pl, hostname.pl, getopts.pl,
	   getopt.pl, getcwd.pl, flush.pl, fastcwd.pl, exceptions.pl, ctime.pl, complete.pl,
	   cacheout.pl, bigrat.pl, bigint.pl, bigfloat.pl, assert.pl, abbrev.pl, dotsh.pl, and
	   timelocal.pl are all now deprecated.  Earlier, Perl's developers intended to remove
	   these libraries from Perl's core for the 5.14.0 release.

	   During final testing before the release of 5.12.0, several developers discovered
	   current production code using these ancient libraries, some inside the Perl core
	   itself.  Accordingly, the pumpking granted them a stay of execution. They will begin
	   to warn about their deprecation in the 5.14.0 release and will be removed in the
	   5.16.0 release.

Unicode overhaul
       Perl's developers have made a concerted effort to update Perl to be in sync with the
       latest Unicode standard. Changes for this include:

       Perl can now handle every Unicode character property. New documentation, perluniprops,
       lists all available non-Unihan character properties. By default, perl does not expose
       Unihan, deprecated or Unicode-internal properties.  See below for more details on these;
       there is also a section in the pod listing them, and explaining why they are not exposed.

       Perl now fully supports the Unicode compound-style of using "=" and ":" in writing regular
       expressions: "\p{property=value}" and "\p{property:value}" (both of which mean the same
       thing).

       Perl now fully supports the Unicode loose matching rules for text between the braces in
       "\p{...}" constructs. In addition, Perl allows underscores between digits of numbers.

       Perl now accepts all the Unicode-defined synonyms for properties and property values.

       "qr/\X/", which matches a Unicode logical character, has been expanded to work better with
       various Asian languages. It now is defined as an extended grapheme cluster. (See
       <http://www.unicode.org/reports/tr29/>).  Anything matched previously and that made sense
       will continue to be accepted.   Additionally:

       o   "\X" will not break apart a "CR LF" sequence.

       o   "\X" will now match a sequence which includes the "ZWJ" and "ZWNJ" characters.

       o   "\X" will now always match at least one character, including an initial mark.  Marks
	   generally come after a base character, but it is possible in Unicode to have them in
	   isolation, and "\X" will now handle that case, for example at the beginning of a line,
	   or after a "ZWSP". And this is the part where "\X" doesn't match the things that it
	   used to that don't make sense. Formerly, for example, you could have the nonsensical
	   case of an accented LF.

       o   "\X" will now match a (Korean) Hangul syllable sequence, and the Thai and Lao
	   exception cases.

       Otherwise, this change should be transparent for the non-affected languages.

       "\p{...}" matches using the Canonical_Combining_Class property were completely broken in
       previous releases of Perl.  They should now work correctly.

       Before Perl 5.12, the Unicode "Decomposition_Type=Compat" property and a Perl extension
       had the same name, which led to neither matching all the correct values (with more than
       100 mistakes in one, and several thousand in the other). The Perl extension has now been
       renamed to be "Decomposition_Type=Noncanonical" (short: "dt=noncanon"). It has the same
       meaning as was previously intended, namely the union of all the non-canonical
       Decomposition types, with Unicode "Compat" being just one of those.

       "\p{Decomposition_Type=Canonical}" now includes the Hangul syllables.

       "\p{Uppercase}" and "\p{Lowercase}" now work as the Unicode standard says they should.
       This means they each match a few more characters than they used to.

       "\p{Cntrl}" now matches the same characters as "\p{Control}". This means it no longer will
       match Private Use (gc=co), Surrogates (gc=cs), nor Format (gc=cf) code points. The Format
       code points represent the biggest possible problem. All but 36 of them are either
       officially deprecated or strongly discouraged from being used. Of those 36, likely the
       most widely used are the soft hyphen (U+00AD), and BOM, ZWSP, ZWNJ, WJ, and similar
       characters, plus bidirectional controls.

       "\p{Alpha}" now matches the same characters as "\p{Alphabetic}". Before 5.12, Perl's
       definition definition included a number of things that aren't really alpha (all marks)
       while omitting many that were. The definitions of "\p{Alnum}" and "\p{Word}" depend on
       Alpha's definition and have changed accordingly.

       "\p{Word}" no longer incorrectly matches non-word characters such as fractions.

       "\p{Print}" no longer matches the line control characters: Tab, LF, CR, FF, VT, and NEL.
       This brings it in line with standards and the documentation.

       "\p{XDigit}" now matches the same characters as "\p{Hex_Digit}". This means that in
       addition to the characters it currently matches, "[A-Fa-f0-9]", it will also match the 22
       fullwidth equivalents, for example U+FF10: FULLWIDTH DIGIT ZERO.

       The Numeric type property has been extended to include the Unihan characters.

       There is a new Perl extension, the 'Present_In', or simply 'In', property. This is an
       extension of the Unicode Age property, but "\p{In=5.0}" matches any code point whose usage
       has been determined as of Unicode version 5.0. The "\p{Age=5.0}" only matches code points
       added in precisely version 5.0.

       A number of properties now have the correct values for unassigned code points. The
       affected properties are Bidi_Class, East_Asian_Width, Joining_Type, Decomposition_Type,
       Hangul_Syllable_Type, Numeric_Type, and Line_Break.

       The Default_Ignorable_Code_Point, ID_Continue, and ID_Start properties are now up to date
       with current Unicode definitions.

       Earlier versions of Perl erroneously exposed certain properties that are supposed to be
       Unicode internal-only.  Use of these in regular expressions will now generate, if enabled,
       a deprecation warning message.  The 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.

       It is now possible to change which Unicode properties Perl understands on a per-
       installation basis. As mentioned above, certain properties are turned off by default.
       These include all the Unihan properties (which should be accessible via the CPAN module
       Unicode::Unihan) and any deprecated or Unicode internal-only property that Perl has never
       exposed.

       The generated files in the "lib/unicore/To" directory are now more clearly marked as being
       stable, directly usable by applications.  New hash entries in them give the format of the
       normal entries, which allows for easier machine parsing. Perl can generate files in this
       directory for any property, though most are suppressed.	You can find instructions for
       changing which are written in perluniprops.

Modules and Pragmata
   New Modules and Pragmata
       "autodie"
	   "autodie" is a new lexically-scoped alternative for the "Fatal" module.  The bundled
	   version is 2.06_01. Note that in this release, using a string eval when "autodie" is
	   in effect can cause the autodie behaviour to leak into the surrounding scope. See
	   "BUGS" in autodie for more details.

	   Version 2.06_01 has been added to the Perl core.

       "Compress::Raw::Bzip2"
	   Version 2.024 has been added to the Perl core.

       "overloading"
	   "overloading" allows you to lexically disable or enable overloading for some or all
	   operations.

	   Version 0.001 has been added to the Perl core.

       "parent"
	   "parent" establishes an ISA relationship with base classes at compile time. It
	   provides the key feature of "base" without further unwanted behaviors.

	   Version 0.223 has been added to the Perl core.

       "Parse::CPAN::Meta"
	   Version 1.40 has been added to the Perl core.

       "VMS::DCLsym"
	   Version 1.03 has been added to the Perl core.

       "VMS::Stdio"
	   Version 2.4 has been added to the Perl core.

       "XS::APItest::KeywordRPN"
	   Version 0.003 has been added to the Perl core.

   Updated Pragmata
       "base"
	   Upgraded from version 2.13 to 2.15.

       "bignum"
	   Upgraded from version 0.22 to 0.23.

       "charnames"
	   "charnames" now contains the Unicode NameAliases.txt database file.	This has the
	   effect of adding some extra "\N" character names that formerly wouldn't have been
	   recognised; for example, "\N{LATIN CAPITAL LETTER GHA}".

	   Upgraded from version 1.06 to 1.07.

       "constant"
	   Upgraded from version 1.13 to 1.20.

       "diagnostics"
	   "diagnostics" now supports %.0f formatting internally.

	   "diagnostics" no longer suppresses "Use of uninitialized value in range (or flip)"
	   warnings. [perl #71204]

	   Upgraded from version 1.17 to 1.19.

       "feature"
	   In "feature", the meaning of the ":5.10" and ":5.10.X" feature bundles has changed
	   slightly. The last component, if any (i.e. "X") is simply ignored.  This is predicated
	   on the assumption that new features will not, in general, be added to maintenance
	   releases. So ":5.10" and ":5.10.X" have identical effect. This is a change to the
	   behaviour documented for 5.10.0.

	   "feature" now includes the "unicode_strings" feature:

	       use feature "unicode_strings";

	   This pragma turns on Unicode semantics for the case-changing operations ("uc", "lc",
	   "ucfirst", "lcfirst") on strings that don't have the internal UTF-8 flag set, but that
	   contain single-byte characters between 128 and 255.

	   Upgraded from version 1.11 to 1.16.

       "less"
	   "less" now includes the "stash_name" method to allow subclasses of "less" to pick
	   where in %^H to store their stash.

	   Upgraded from version 0.02 to 0.03.

       "lib"
	   Upgraded from version 0.5565 to 0.62.

       "mro"
	   "mro" is now implemented as an XS extension. The documented interface has not changed.
	   Code relying on the implementation detail that some "mro::" methods happened to be
	   available at all times gets to "keep both pieces".

	   Upgraded from version 1.00 to 1.02.

       "overload"
	   "overload" now allow overloading of 'qr'.

	   Upgraded from version 1.06 to 1.10.

       "threads"
	   Upgraded from version 1.67 to 1.75.

       "threads::shared"
	   Upgraded from version 1.14 to 1.32.

       "version"
	   "version" now has support for "Version number formats" as described earlier in this
	   document and in its own documentation.

	   Upgraded from version 0.74 to 0.82.

       "warnings"
	   "warnings" has a new "warnings::fatal_enabled()" function.  It also includes a new
	   "illegalproto" warning category. See also "New or Changed Diagnostics" for this
	   change.

	   Upgraded from version 1.06 to 1.09.

   Updated Modules
       "Archive::Extract"
	   Upgraded from version 0.24 to 0.38.

       "Archive::Tar"
	   Upgraded from version 1.38 to 1.54.

       "Attribute::Handlers"
	   Upgraded from version 0.79 to 0.87.

       "AutoLoader"
	   Upgraded from version 5.63 to 5.70.

       "B::Concise"
	   Upgraded from version 0.74 to 0.78.

       "B::Debug"
	   Upgraded from version 1.05 to 1.12.

       "B::Deparse"
	   Upgraded from version 0.83 to 0.96.

       "B::Lint"
	   Upgraded from version 1.09 to 1.11_01.

       "CGI"
	   Upgraded from version 3.29 to 3.48.

       "Class::ISA"
	   Upgraded from version 0.33 to 0.36.

	   NOTE: "Class::ISA" is deprecated and may be removed from a future version of Perl.

       "Compress::Raw::Zlib"
	   Upgraded from version 2.008 to 2.024.

       "CPAN"
	   Upgraded from version 1.9205 to 1.94_56.

       "CPANPLUS"
	   Upgraded from version 0.84 to 0.90.

       "CPANPLUS::Dist::Build"
	   Upgraded from version 0.06_02 to 0.46.

       "Data::Dumper"
	   Upgraded from version 2.121_14 to 2.125.

       "DB_File"
	   Upgraded from version 1.816_1 to 1.820.

       "Devel::PPPort"
	   Upgraded from version 3.13 to 3.19.

       "Digest"
	   Upgraded from version 1.15 to 1.16.

       "Digest::MD5"
	   Upgraded from version 2.36_01 to 2.39.

       "Digest::SHA"
	   Upgraded from version 5.45 to 5.47.

       "Encode"
	   Upgraded from version 2.23 to 2.39.

       "Exporter"
	   Upgraded from version 5.62 to 5.64_01.

       "ExtUtils::CBuilder"
	   Upgraded from version 0.21 to 0.27.

       "ExtUtils::Command"
	   Upgraded from version 1.13 to 1.16.

       "ExtUtils::Constant"
	   Upgraded from version 0.2 to 0.22.

       "ExtUtils::Install"
	   Upgraded from version 1.44 to 1.55.

       "ExtUtils::MakeMaker"
	   Upgraded from version 6.42 to 6.56.

       "ExtUtils::Manifest"
	   Upgraded from version 1.51_01 to 1.57.

       "ExtUtils::ParseXS"
	   Upgraded from version 2.18_02 to 2.21.

       "File::Fetch"
	   Upgraded from version 0.14 to 0.24.

       "File::Path"
	   Upgraded from version 2.04 to 2.08_01.

       "File::Temp"
	   Upgraded from version 0.18 to 0.22.

       "Filter::Simple"
	   Upgraded from version 0.82 to 0.84.

       "Filter::Util::Call"
	   Upgraded from version 1.07 to 1.08.

       "Getopt::Long"
	   Upgraded from version 2.37 to 2.38.

       "IO"
	   Upgraded from version 1.23_01 to 1.25_02.

       "IO::Zlib"
	   Upgraded from version 1.07 to 1.10.

       "IPC::Cmd"
	   Upgraded from version 0.40_1 to 0.54.

       "IPC::SysV"
	   Upgraded from version 1.05 to 2.01.

       "Locale::Maketext"
	   Upgraded from version 1.12 to 1.14.

       "Locale::Maketext::Simple"
	   Upgraded from version 0.18 to 0.21.

       "Log::Message"
	   Upgraded from version 0.01 to 0.02.

       "Log::Message::Simple"
	   Upgraded from version 0.04 to 0.06.

       "Math::BigInt"
	   Upgraded from version 1.88 to 1.89_01.

       "Math::BigInt::FastCalc"
	   Upgraded from version 0.16 to 0.19.

       "Math::BigRat"
	   Upgraded from version 0.21 to 0.24.

       "Math::Complex"
	   Upgraded from version 1.37 to 1.56.

       "Memoize"
	   Upgraded from version 1.01_02 to 1.01_03.

       "MIME::Base64"
	   Upgraded from version 3.07_01 to 3.08.

       "Module::Build"
	   Upgraded from version 0.2808_01 to 0.3603.

       "Module::CoreList"
	   Upgraded from version 2.12 to 2.29.

       "Module::Load"
	   Upgraded from version 0.12 to 0.16.

       "Module::Load::Conditional"
	   Upgraded from version 0.22 to 0.34.

       "Module::Loaded"
	   Upgraded from version 0.01 to 0.06.

       "Module::Pluggable"
	   Upgraded from version 3.6 to 3.9.

       "Net::Ping"
	   Upgraded from version 2.33 to 2.36.

       "NEXT"
	   Upgraded from version 0.60_01 to 0.64.

       "Object::Accessor"
	   Upgraded from version 0.32 to 0.36.

       "Package::Constants"
	   Upgraded from version 0.01 to 0.02.

       "PerlIO"
	   Upgraded from version 1.04 to 1.06.

       "Pod::Parser"
	   Upgraded from version 1.35 to 1.37.

       "Pod::Perldoc"
	   Upgraded from version 3.14_02 to 3.15_02.

       "Pod::Plainer"
	   Upgraded from version 0.01 to 1.02.

	   NOTE: "Pod::Plainer" is deprecated and may be removed from a future version of Perl.

       "Pod::Simple"
	   Upgraded from version 3.05 to 3.13.

       "Safe"
	   Upgraded from version 2.12 to 2.22.

       "SelfLoader"
	   Upgraded from version 1.11 to 1.17.

       "Storable"
	   Upgraded from version 2.18 to 2.22.

       "Switch"
	   Upgraded from version 2.13 to 2.16.

	   NOTE: "Switch" is deprecated and may be removed from a future version of Perl.

       "Sys::Syslog"
	   Upgraded from version 0.22 to 0.27.

       "Term::ANSIColor"
	   Upgraded from version 1.12 to 2.02.

       "Term::UI"
	   Upgraded from version 0.18 to 0.20.

       "Test"
	   Upgraded from version 1.25 to 1.25_02.

       "Test::Harness"
	   Upgraded from version 2.64 to 3.17.

       "Test::Simple"
	   Upgraded from version 0.72 to 0.94.

       "Text::Balanced"
	   Upgraded from version 2.0.0 to 2.02.

       "Text::ParseWords"
	   Upgraded from version 3.26 to 3.27.

       "Text::Soundex"
	   Upgraded from version 3.03 to 3.03_01.

       "Thread::Queue"
	   Upgraded from version 2.00 to 2.11.

       "Thread::Semaphore"
	   Upgraded from version 2.01 to 2.09.

       "Tie::RefHash"
	   Upgraded from version 1.37 to 1.38.

       "Time::HiRes"
	   Upgraded from version 1.9711 to 1.9719.

       "Time::Local"
	   Upgraded from version 1.18 to 1.1901_01.

       "Time::Piece"
	   Upgraded from version 1.12 to 1.15.

       "Unicode::Collate"
	   Upgraded from version 0.52 to 0.52_01.

       "Unicode::Normalize"
	   Upgraded from version 1.02 to 1.03.

       "Win32"
	   Upgraded from version 0.34 to 0.39.

       "Win32API::File"
	   Upgraded from version 0.1001_01 to 0.1101.

       "XSLoader"
	   Upgraded from version 0.08 to 0.10.

   Removed Modules and Pragmata
       "attrs"
	   Removed from the Perl core.	Prior version was 1.02.

       "CPAN::API::HOWTO"
	   Removed from the Perl core.	Prior version was 'undef'.

       "CPAN::DeferedCode"
	   Removed from the Perl core.	Prior version was 5.50.

       "CPANPLUS::inc"
	   Removed from the Perl core.	Prior version was 'undef'.

       "DCLsym"
	   Removed from the Perl core.	Prior version was 1.03.

       "ExtUtils::MakeMaker::bytes"
	   Removed from the Perl core.	Prior version was 6.42.

       "ExtUtils::MakeMaker::vmsish"
	   Removed from the Perl core.	Prior version was 6.42.

       "Stdio"
	   Removed from the Perl core.	Prior version was 2.3.

       "Test::Harness::Assert"
	   Removed from the Perl core.	Prior version was 0.02.

       "Test::Harness::Iterator"
	   Removed from the Perl core.	Prior version was 0.02.

       "Test::Harness::Point"
	   Removed from the Perl core.	Prior version was 0.01.

       "Test::Harness::Results"
	   Removed from the Perl core.	Prior version was 0.01.

       "Test::Harness::Straps"
	   Removed from the Perl core.	Prior version was 0.26_01.

       "Test::Harness::Util"
	   Removed from the Perl core.	Prior version was 0.01.

       "XSSymSet"
	   Removed from the Perl core.	Prior version was 1.1.

   Deprecated Modules and Pragmata
       See "Deprecated Modules" above.

Documentation
   New Documentation
       o   perlhaiku contains instructions on how to build perl for the Haiku platform.

       o   perlmroapi describes the new interface for pluggable Method Resolution Orders.

       o   perlperf, by Richard Foley, provides an introduction to the use of performance and
	   optimization techniques which can be used with particular reference to perl programs.

       o   perlrepository describes how to access the perl source using the git version control
	   system.

       o   perlpolicy extends the "Social contract about contributed modules" into the beginnings
	   of a document on Perl porting policies.

   Changes to Existing Documentation
       o   The various large Changes* files (which listed every change made to perl over the last
	   18 years) have been removed, and replaced by a small file, also called Changes, which
	   just explains how that same information may be extracted from the git version control
	   system.

       o   Porting/patching.pod has been deleted, as it mainly described interacting with the old
	   Perforce-based repository, which is now obsolete.  Information still relevant has been
	   moved to perlrepository.

       o   The syntax "unless (EXPR) BLOCK else BLOCK" is now documented as valid, as is the
	   syntax "unless (EXPR) BLOCK elsif (EXPR) BLOCK ... else BLOCK", although actually
	   using the latter may not be the best idea for the readability of your source code.

       o   Documented -X overloading.

       o   Documented that "when()" treats specially most of the filetest operators

       o   Documented "when" as a syntax modifier.

       o   Eliminated "Old Perl threads tutorial", which described 5005 threads.

	   pod/perlthrtut.pod is the same material reworked for ithreads.

       o   Correct previous documentation: v-strings are not deprecated

	   With version objects, we need them to use MODULE VERSION syntax. This patch removes
	   the deprecation notice.

       o   Security contact information is now part of perlsec.

       o   A significant fraction of the core documentation has been updated to clarify the
	   behavior of Perl's Unicode handling.

	   Much of the remaining core documentation has been reviewed and edited for clarity,
	   consistent use of language, and to fix the spelling of Tom Christiansen's name.

       o   The Pod specification (perlpodspec) has been updated to bring the specification in
	   line with modern usage already supported by most Pod systems. A parameter string may
	   now follow the format name in a "begin/end" region. Links to URIs with a text
	   description are now allowed. The usage of "L<"section">" has been marked as
	   deprecated.

       o   if.pm has been documented in "use" in perlfunc as a means to get conditional loading
	   of modules despite the implicit BEGIN block around "use".

       o   The documentation for $1 in perlvar.pod has been clarified.

       o   "\N{U+code point}" is now documented.

Selected Performance Enhancements
       o   A new internal cache means that "isa()" will often be faster.

       o   The implementation of "C3" Method Resolution Order has been optimised - linearisation
	   for classes with single inheritance is 40% faster. Performance for multiple
	   inheritance is unchanged.

       o   Under "use locale", the locale-relevant information is now cached on read-only values,
	   such as the list returned by "keys %hash". This makes operations such as "sort keys
	   %hash" in the scope of "use locale" much faster.

       o   Empty "DESTROY" methods are no longer called.

       o   "Perl_sv_utf8_upgrade()" is now faster.

       o   "keys" on empty hash is now faster.

       o   "if (%foo)" has been optimized to be faster than "if (keys %foo)".

       o   The string repetition operator ("$str x $num") is now several times faster when $str
	   has length one or $num is large.

       o   Reversing an array to itself (as in "@a = reverse @a") in void context now happens in-
	   place and is several orders of magnitude faster than it used to be. It will also
	   preserve non-existent elements whenever possible, i.e. for non magical arrays or tied
	   arrays with "EXISTS" and "DELETE" methods.

Installation and Configuration Improvements
       o   perlapi, perlintern, perlmodlib and perltoc are now all generated at build time,
	   rather than being shipped as part of the release.

       o   If "vendorlib" and "vendorarch" are the same, then they are only added to @INC once.

       o   $Config{usedevel} and the C-level "PERL_USE_DEVEL" are now defined if perl is built
	   with  "-Dusedevel".

       o   Configure will enable use of "-fstack-protector", to provide protection against stack-
	   smashing attacks, if the compiler supports it.

       o   Configure will now determine the correct prototypes for re-entrant functions and for
	   "gconvert" if you are using a C++ compiler rather than a C compiler.

       o   On Unix, if you build from a tree containing a git repository, the configuration
	   process will note the commit hash you have checked out, for display in the output of
	   "perl -v" and "perl -V". Unpushed local commits are automatically added to the list of
	   local patches displayed by "perl -V".

       o   Perl now supports SystemTap's "dtrace" compatibility layer and an issue with linking
	   "miniperl" has been fixed in the process.

       o   perldoc now uses "less -R" instead of "less" for improved behaviour in the face of
	   "groff"'s new usage of ANSI escape codes.

       o   "perl -V" now reports use of the compile-time options "USE_PERL_ATOF" and
	   "USE_ATTRIBUTES_FOR_PERLIO".

       o   As part of the flattening of ext, all extensions on all platforms are built by
	   make_ext.pl. This replaces the Unix-specific ext/util/make_ext, VMS-specific
	   make_ext.com and Win32-specific win32/buildext.pl.

Internal Changes
       Each release of Perl sees numerous internal changes which shouldn't affect day to day
       usage but may still be notable for developers working with Perl's source code.

       o   The J.R.R. Tolkien quotes at the head of C source file have been checked and proper
	   citations added, thanks to a patch from Tom Christiansen.

       o   The internal structure of the dual-life modules traditionally found in the lib/ and
	   ext/ directories in the perl source has changed significantly. Where possible, dual-
	   lifed modules have been extracted from lib/ and ext/.

	   Dual-lifed modules maintained by Perl's developers as part of the Perl core now live
	   in dist/.  Dual-lifed modules maintained primarily on CPAN now live in cpan/.  When
	   reporting a bug in a module located under cpan/, please send your bug report directly
	   to the module's bug tracker or author, rather than Perl's bug tracker.

       o   "\N{...}" now compiles better, always forces UTF-8 internal representation

	   Perl's developers have fixed several problems with the recognition of "\N{...}"
	   constructs.	As part of this, perl will store any scalar or regex containing
	   "\N{name}" or "\N{U+code point}" in its definition in UTF-8 format. (This was true
	   previously for all occurrences of "\N{name}" that did not use a custom translator, but
	   now it's always true.)

       o   Perl_magic_setmglob now knows about globs, fixing RT #71254.

       o   "SVt_RV" no longer exists. RVs are now stored in IVs.

       o   "Perl_vcroak()" now accepts a null first argument. In addition, a full audit was made
	   of the "not NULL" compiler annotations, and those for several other internal functions
	   were corrected.

       o   New macros "dSAVEDERRNO", "dSAVE_ERRNO", "SAVE_ERRNO", "RESTORE_ERRNO" have been added
	   to formalise the temporary saving of the "errno" variable.

       o   The function "Perl_sv_insert_flags" has been added to augment "Perl_sv_insert".

       o   The function "Perl_newSV_type(type)" has been added, equivalent to "Perl_newSV()"
	   followed by "Perl_sv_upgrade(type)".

       o   The function "Perl_newSVpvn_flags()" has been added, equivalent to "Perl_newSVpvn()"
	   and then performing the action relevant to the flag.

	   Two flag bits are currently supported.

	   o   "SVf_UTF8" will call "SvUTF8_on()" for you. (Note that this does not convert an
	       sequence of ISO 8859-1 characters to UTF-8). A wrapper, "newSVpvn_utf8()" is
	       available for this.

	   o   "SVs_TEMP" now calls "Perl_sv_2mortal()" on the new SV.

	   There is also a wrapper that takes constant strings, "newSVpvs_flags()".

       o   The function "Perl_croak_xs_usage" has been added as a wrapper to "Perl_croak".

       o   Perl now exports the functions "PerlIO_find_layer" and "PerlIO_list_alloc".

       o   "PL_na" has been exterminated from the core code, replaced by local STRLEN
	   temporaries, or "*_nolen()" calls. Either approach is faster than "PL_na", which is a
	   pointer dereference into the interpreter structure under ithreads, and a global
	   variable otherwise.

       o   "Perl_mg_free()" used to leave freed memory accessible via "SvMAGIC()" on the scalar.
	   It now updates the linked list to remove each piece of magic as it is freed.

       o   Under ithreads, the regex in "PL_reg_curpm" is now reference counted. This eliminates
	   a lot of hackish workarounds to cope with it not being reference counted.

       o   "Perl_mg_magical()" would sometimes incorrectly turn on "SvRMAGICAL()".  This has been
	   fixed.

       o   The public IV and NV flags are now not set if the string value has trailing "garbage".
	   This behaviour is consistent with not setting the public IV or NV flags if the value
	   is out of range for the type.

       o   Uses of "Nullav", "Nullcv", "Nullhv", "Nullop", "Nullsv" etc have been replaced by
	   "NULL" in the core code, and non-dual-life modules, as "NULL" is clearer to those
	   unfamiliar with the core code.

       o   A macro MUTABLE_PTR(p) has been added, which on (non-pedantic) gcc will not cast away
	   "const", returning a "void *". Macros "MUTABLE_SV(av)", "MUTABLE_SV(cv)" etc build on
	   this, casting to "AV *" etc without casting away "const". This allows proper compile-
	   time auditing of "const" correctness in the core, and helped picked up some errors
	   (now fixed).

       o   Macros "mPUSHs()" and "mXPUSHs()" have been added, for pushing SVs on the stack and
	   mortalizing them.

       o   Use of the private structure "mro_meta" has changed slightly. Nothing outside the core
	   should be accessing this directly anyway.

       o   A new tool, Porting/expand-macro.pl has been added, that allows you to view how a C
	   preprocessor macro would be expanded when compiled.	This is handy when trying to
	   decode the macro hell that is the perl guts.

Testing
   Testing improvements
       Parallel tests
	   The core distribution can now run its regression tests in parallel on Unix-like
	   platforms. Instead of running "make test", set "TEST_JOBS" in your environment to the
	   number of tests to run in parallel, and run "make test_harness". On a Bourne-like
	   shell, this can be done as

	       TEST_JOBS=3 make test_harness  # Run 3 tests in parallel

	   An environment variable is used, rather than parallel make itself, because
	   TAP::Harness needs to be able to schedule individual non-conflicting test scripts
	   itself, and there is no standard interface to "make" utilities to interact with their
	   job schedulers.

	   Note that currently some test scripts may fail when run in parallel (most notably
	   "ext/IO/t/io_dir.t"). If necessary run just the failing scripts again sequentially and
	   see if the failures go away.

       Test harness flexibility
	   It's now possible to override "PERL5OPT" and friends in t/TEST

       Test watchdog
	   Several tests that have the potential to hang forever if they fail now incorporate a
	   "watchdog" functionality that will kill them after a timeout, which helps ensure that
	   "make test" and "make test_harness" run to completion automatically.

   New Tests
       Perl's developers have added a number of new tests to the core.	In addition to the items
       listed below, many modules updated from CPAN incorporate new tests.

       o   Significant cleanups to core tests to ensure that language and interpreter features
	   are not used before they're tested.

       o   "make test_porting" now runs a number of important pre-commit checks which might be of
	   use to anyone working on the Perl core.

       o   t/porting/podcheck.t automatically checks the well-formedness of POD found in all .pl,
	   .pm and .pod files in the MANIFEST, other than in dual-lifed modules which are
	   primarily maintained outside the Perl core.

       o   t/porting/manifest.t now tests that all files listed in MANIFEST are present.

       o   t/op/while_readdir.t tests that a bare readdir in while loop sets $_.

       o   t/comp/retainedlines.t checks that the debugger can retain source lines from "eval".

       o   t/io/perlio_fail.t checks that bad layers fail.

       o   t/io/perlio_leaks.t checks that PerlIO layers are not leaking.

       o   t/io/perlio_open.t checks that certain special forms of open work.

       o   t/io/perlio.t includes general PerlIO tests.

       o   t/io/pvbm.t checks that there is no unexpected interaction between the internal types
	   "PVBM" and "PVGV".

       o   t/mro/package_aliases.t checks that mro works properly in the presence of aliased
	   packages.

       o   t/op/dbm.t tests "dbmopen" and "dbmclose".

       o   t/op/index_thr.t tests the interaction of "index" and threads.

       o   t/op/pat_thr.t tests the interaction of esoteric patterns and threads.

       o   t/op/qr_gc.t tests that "qr" doesn't leak.

       o   t/op/reg_email_thr.t tests the interaction of regex recursion and threads.

       o   t/op/regexp_qr_embed_thr.t tests the interaction of patterns with embedded "qr//" and
	   threads.

       o   t/op/regexp_unicode_prop.t tests Unicode properties in regular expressions.

       o   t/op/regexp_unicode_prop_thr.t tests the interaction of Unicode properties and
	   threads.

       o   t/op/reg_nc_tie.t tests the tied methods of "Tie::Hash::NamedCapture".

       o   t/op/reg_posixcc.t checks that POSIX character classes behave consistently.

       o   t/op/re.t checks that exportable "re" functions in universal.c work.

       o   t/op/setpgrpstack.t checks that "setpgrp" works.

       o   t/op/substr_thr.t tests the interaction of "substr" and threads.

       o   t/op/upgrade.t checks that upgrading and assigning scalars works.

       o   t/uni/lex_utf8.t checks that Unicode in the lexer works.

       o   t/uni/tie.t checks that Unicode and "tie" work.

       o   t/comp/final_line_num.t tests whether line numbers are correct at EOF

       o   t/comp/form_scope.t tests format scoping.

       o   t/comp/line_debug.t tests whether "@{"_<$file"}" works.

       o   t/op/filetest_t.t tests if -t file test works.

       o   t/op/qr.t tests "qr".

       o   t/op/utf8cache.t tests malfunctions of the utf8 cache.

       o   t/re/uniprops.t test unicodes "\p{}" regex constructs.

       o   t/op/filehandle.t tests some suitably portable filetest operators to check that they
	   work as expected, particularly in the light of some internal changes made in how
	   filehandles are blessed.

       o   t/op/time_loop.t tests that unix times greater than "2**63", which can now be handed
	   to "gmtime" and "localtime", do not cause an internal overflow or an excessively long
	   loop.

New or Changed Diagnostics
   New Diagnostics
       o   SV allocation tracing has been added to the diagnostics enabled by "-Dm".  The tracing
	   can alternatively output via the "PERL_MEM_LOG" mechanism, if that was enabled when
	   the perl binary was compiled.

       o   Smartmatch resolution tracing has been added as a new diagnostic. Use "-DM" to enable
	   it.

       o   A new debugging flag "-DB" now dumps subroutine definitions, leaving "-Dx" for its
	   original purpose of dumping syntax trees.

       o   Perl 5.12 provides a number of new diagnostic messages to help you write better code.
	   See perldiag for details of these new messages.

	   o   "Bad plugin affecting keyword '%s'"

	   o   "gmtime(%.0f) too large"

	   o   "Lexing code attempted to stuff non-Latin-1 character into Latin-1 input"

	   o   "Lexing code internal error (%s)"

	   o   "localtime(%.0f) too large"

	   o   "Overloaded dereference did not return a reference"

	   o   "Overloaded qr did not return a REGEXP"

	   o   "Perl_pmflag() is deprecated, and will be removed from the XS API"

	   o   "lvalue attribute ignored after the subroutine has been defined"

	       This new warning is issued when one attempts to mark a subroutine as lvalue after
	       it has been defined.

	   o   Perl now warns you if "++" or "--" are unable to change the value because it's
	       beyond the limit of representation.

	       This uses a new warnings category: "imprecision".

	   o   "lc", "uc", "lcfirst", and "ucfirst" warn when passed undef.

	   o   "Show constant in "Useless use of a constant in void context""

	   o   "Prototype after '%s'"

	   o   "panic: sv_chop %s"

	       This new fatal error occurs when the C routine "Perl_sv_chop()" was passed a
	       position that is not within the scalar's string buffer. This could be caused by
	       buggy XS code, and at this point recovery is not possible.

	   o   The fatal error "Malformed UTF-8 returned by \N" is now produced if the
	       "charnames" handler returns malformed UTF-8.

	   o   If an unresolved named character or sequence was encountered when compiling a
	       regex pattern then the fatal error "\N{NAME} must be resolved by the lexer" is now
	       produced. This can happen, for example, when using a single-quotish context like
	       "$re = '\N{SPACE}'; /$re/;". See perldiag for more examples of how the lexer can
	       get bypassed.

	   o   "Invalid hexadecimal number in \N{U+...}" is a new fatal error triggered when the
	       character constant represented by "..." is not a valid hexadecimal number.

	   o   The new meaning of "\N" as "[^\n]" is not valid in a bracketed character class,
	       just like "." in a character class loses its special meaning, and will cause the
	       fatal error "\N in a character class must be a named character: \N{...}".

	   o   The rules on what is legal for the "..." in "\N{...}" have been tightened up so
	       that unless the "..." begins with an alphabetic character and continues with a
	       combination of alphanumerics, dashes, spaces, parentheses or colons then the
	       warning "Deprecated character(s) in \N{...} starting at '%s'" is now issued.

	   o   The warning "Using just the first characters returned by \N{}" will be issued if
	       the "charnames" handler returns a sequence of characters which exceeds the limit
	       of the number of characters that can be used. The message will indicate which
	       characters were used and which were discarded.

   Changed Diagnostics
       A number of existing diagnostic messages have been improved or corrected:

       o   A new warning category "illegalproto" allows finer-grained control of warnings around
	   function prototypes.

	   The two warnings:

	   "Illegal character in prototype for %s : %s"
	   "Prototype after '%c' for %s : %s"

	   have been moved from the "syntax" top-level warnings category into a new first-level
	   category, "illegalproto". These two warnings are currently the only ones emitted
	   during parsing of an invalid/illegal prototype, so one can now use

	     no warnings 'illegalproto';

	   to suppress only those, but not other syntax-related warnings. Warnings where
	   prototypes are changed, ignored, or not met are still in the "prototype" category as
	   before.

       o   "Deep recursion on subroutine "%s""

	   It is now possible to change the depth threshold for this warning from the default of
	   100, by recompiling the perl binary, setting the C pre-processor macro
	   "PERL_SUB_DEPTH_WARN" to the desired value.

       o   "Illegal character in prototype" warning is now more precise when reporting illegal
	   characters after _

       o   mro merging error messages are now very similar to those produced by Algorithm::C3.

       o   Amelioration of the error message "Unrecognized character %s in column %d"

	   Changes the error message to "Unrecognized character %s; marked by <-- HERE after
	   %s<-- HERE near column %d". This should make it a little simpler to spot and correct
	   the suspicious character.

       o   Perl now explicitly points to $. when it causes an uninitialized warning for ranges in
	   scalar context.

       o   "split" now warns when called in void context.

       o   "printf"-style functions called with too few arguments will now issue the warning
	   "Missing argument in %s" [perl #71000]

       o   Perl now properly returns a syntax error instead of segfaulting if "each", "keys", or
	   "values" is used without an argument.

       o   "tell()" now fails properly if called without an argument and when no previous file
	   was read.

	   "tell()" now returns "-1", and sets errno to "EBADF", thus restoring the 5.8.x
	   behaviour.

       o   "overload" no longer implicitly unsets fallback on repeated 'use overload' lines.

       o   POSIX::strftime() can now handle Unicode characters in the format string.

       o   The "syntax" category was removed from 5 warnings that should only be in "deprecated".

       o   Three fatal "pack"/"unpack" error messages have been normalized to "panic: %s"

       o   "Unicode character is illegal" has been rephrased to be more accurate

	   It now reads "Unicode non-character is illegal in interchange" and the perldiag
	   documentation has been expanded a bit.

       o   Currently, all but the first of the several characters that the "charnames" handler
	   may return are discarded when used in a regular expression pattern bracketed character
	   class. If this happens then the warning "Using just the first character returned by
	   \N{} in character class" will be issued.

       o   The warning "Missing right brace on \N{} or unescaped left brace after \N.  Assuming
	   the latter" will be issued if Perl encounters a "\N{" but doesn't find a matching "}".
	   In this case Perl doesn't know if it was mistakenly omitted, or if "match non-newline"
	   followed by "match a "{"" was desired.  It assumes the latter because that is actually
	   a valid interpretation as written, unlike the other case.  If you meant the former,
	   you need to add the matching right brace.  If you did mean the latter, you can silence
	   this warning by writing instead "\N\{".

       o   "gmtime" and "localtime" called with numbers smaller than they can reliably handle
	   will now issue the warnings "gmtime(%.0f) too small" and "localtime(%.0f) too small".

       The following diagnostic messages have been removed:

       o   "Runaway format"

       o   "Can't locate package %s for the parents of %s"

	   In general this warning it only got produced in conjunction with other warnings, and
	   removing it allowed an ISA lookup optimisation to be added.

       o   "v-string in use/require is non-portable"

Utility Changes
       o   h2ph now looks in "include-fixed" too, which is a recent addition to gcc's search
	   path.

       o   h2xs no longer incorrectly treats enum values like macros.  It also now handles C++
	   style comments ("//") properly in enums.

       o   perl5db.pl now supports "LVALUE" subroutines.  Additionally, the debugger now
	   correctly handles proxy constant subroutines, and subroutine stubs.

       o   perlbug now uses %Module::CoreList::bug_tracker to print out upstream bug tracker
	   URLs.  If a user identifies a particular module as the topic of their bug report and
	   we're able to divine the URL for its upstream bug tracker, perlbug now provide a
	   message to the user explaining that the core copies the CPAN version directly, and
	   provide the URL for reporting the bug directly to the upstream author.

	   perlbug no longer reports "Message sent" when it hasn't actually sent the message

       o   perlthanks is a new utility for sending non-bug-reports to the authors and maintainers
	   of Perl. Getting nothing but bug reports can become a bit demoralising. If Perl 5.12
	   works well for you, please try out perlthanks. It will make the developers smile.

       o   Perl's developers have fixed bugs in a2p having to do with the "match()" operator in
	   list context.  Additionally, a2p no longer generates code that uses the $[ variable.

Selected Bug Fixes
       o   U+0FFFF is now a legal character in regular expressions.

       o   pp_qr now always returns a new regexp SV. Resolves RT #69852.

	   Instead of returning a(nother) reference to the (pre-compiled) regexp in the optree,
	   use reg_temp_copy() to create a copy of it, and return a reference to that. This
	   resolves issues about Regexp::DESTROY not being called in a timely fashion (the
	   original bug tracked by RT #69852), as well as bugs related to blessing regexps, and
	   of assigning to regexps, as described in correspondence added to the ticket.

	   It transpires that we also need to undo the SvPVX() sharing when ithreads cloning a
	   Regexp SV, because mother_re is set to NULL, instead of a cloned copy of the
	   mother_re. This change might fix bugs with regexps and threads in certain other
	   situations, but as yet neither tests nor bug reports have indicated any problems, so
	   it might not actually be an edge case that it's possible to reach.

       o   Several compilation errors and segfaults when perl was built with "-Dmad" were fixed.

       o   Fixes for lexer API changes in 5.11.2 which broke NYTProf's savesrc option.

       o   "-t" should only return TRUE for file handles connected to a TTY

	   The Microsoft C version of "isatty()" returns TRUE for all character mode devices,
	   including the /dev/null-style "nul" device and printers like "lpt1".

       o   Fixed a regression caused by commit fafafbaf which caused a panic during parameter
	   passing [perl #70171]

       o   On systems which in-place edits without backup files, -i'*' now works as the
	   documentation says it does [perl #70802]

       o   Saving and restoring magic flags no longer loses readonly flag.

       o   The malformed syntax "grep EXPR LIST" (note the missing comma) no longer causes abrupt
	   and total failure.

       o   Regular expressions compiled with "qr{}" literals properly set "$'" when matching
	   again.

       o   Using named subroutines with "sort" should no longer lead to bus errors [perl #71076]

       o   Numerous bugfixes catch small issues caused by the recently-added Lexer API.

       o   Smart match against @_ sometimes gave false negatives. [perl #71078]

       o   $@ may now be assigned a read-only value (without error or busting the stack).

       o   "sort" called recursively from within an active comparison subroutine no longer causes
	   a bus error if run multiple times. [perl #71076]

       o   Tie::Hash::NamedCapture::* will not abort if passed bad input (RT #71828)

       o   @_ and $_ no longer leak under threads (RT #34342 and #41138, also #70602, #70974)

       o   "-I" on shebang line now adds directories in front of @INC as documented, and as does
	   "-I" when specified on the command-line.

       o   "kill" is now fatal when called on non-numeric process identifiers.	Previously, an
	   "undef" process identifier would be interpreted as a request to kill process 0, which
	   would terminate the current process group on POSIX systems. Since process identifiers
	   are always integers, killing a non-numeric process is now fatal.

       o   5.10.0 inadvertently disabled an optimisation, which caused a measurable performance
	   drop in list assignment, such as is often used to assign function parameters from @_.
	   The optimisation has been re-instated, and the performance regression fixed. (This fix
	   is also present in 5.10.1)

       o   Fixed memory leak on "while(1) { map 1, 1 }" [RT #53038].

       o   Some potential coredumps in PerlIO fixed [RT #57322,54828].

       o   The debugger now works with lvalue subroutines.

       o   The debugger's "m" command was broken on modules that defined constants [RT #61222].

       o   "crypt" and string complement could return tainted values for untainted arguments [RT
	   #59998].

       o   The "-i".suffix command-line switch now recreates the file using restricted
	   permissions, before changing its mode to match the original file. This eliminates a
	   potential race condition [RT #60904].

       o   On some Unix systems, the value in $? would not have the top bit set ("$? & 128") even
	   if the child core dumped.

       o   Under some circumstances, $^R could incorrectly become undefined [RT #57042].

       o   In the XS API, various hash functions, when passed a pre-computed hash where the key
	   is UTF-8, might result in an incorrect lookup.

       o   XS code including XSUB.h before perl.h gave a compile-time error [RT #57176].

       o   "$object->isa('Foo')" would report false if the package "Foo" didn't exist, even if
	   the object's @ISA contained "Foo".

       o   Various bugs in the new-to 5.10.0 mro code, triggered by manipulating @ISA, have been
	   found and fixed.

       o   Bitwise operations on references could crash the interpreter, e.g.  "$x=\$y; $x |=
	   "foo"" [RT #54956].

       o   Patterns including alternation might be sensitive to the internal UTF-8
	   representation, e.g.

	       my $byte = chr(192);
	       my $utf8 = chr(192); utf8::upgrade($utf8);
	       $utf8 =~ /$byte|X}/i;	   # failed in 5.10.0

       o   Within UTF8-encoded Perl source files (i.e. where "use utf8" is in effect), double-
	   quoted literal strings could be corrupted where a "\xNN", "\0NNN" or "\N{}" is
	   followed by a literal character with ordinal value greater than 255 [RT #59908].

       o   "B::Deparse" failed to correctly deparse various constructs: "readpipe STRING" [RT
	   #62428], "CORE::require(STRING)" [RT #62488], "sub foo(_)" [RT #62484].

       o   Using "setpgrp" with no arguments could corrupt the perl stack.

       o   The block form of "eval" is now specifically trappable by "Safe" and "ops". Previously
	   it was erroneously treated like string "eval".

       o   In 5.10.0, the two characters "[~" were sometimes parsed as the smart match operator
	   ("~~") [RT #63854].

       o   In 5.10.0, the "*" quantifier in patterns was sometimes treated as "{0,32767}" [RT
	   #60034, #60464]. For example, this match would fail:

	       ("ab" x 32768) =~ /^(ab)*$/

       o   "shmget" was limited to a 32 bit segment size on a 64 bit OS [RT #63924].

       o   Using "next" or "last" to exit a "given" block no longer produces a spurious warning
	   like the following:

	       Exiting given via last at foo.pl line 123

       o   Assigning a format to a glob could corrupt the format; e.g.:

		*bar=*foo{FORMAT}; # foo format now bad

       o   Attempting to coerce a typeglob to a string or number could cause an assertion
	   failure. The correct error message is now generated, "Can't coerce GLOB to $type".

       o   Under "use filetest 'access'", "-x" was using the wrong access mode. This has been
	   fixed [RT #49003].

       o   "length" on a tied scalar that returned a Unicode value would not be correct the first
	   time. This has been fixed.

       o   Using an array "tie" inside in array "tie" could SEGV. This has been fixed. [RT
	   #51636]

       o   A race condition inside "PerlIOStdio_close()" has been identified and fixed. This used
	   to cause various threading issues, including SEGVs.

       o   In "unpack", the use of "()" groups in scalar context was internally placing a list on
	   the interpreter's stack, which manifested in various ways, including SEGVs. This is
	   now fixed [RT #50256].

       o   Magic was called twice in "substr", "\&$x", "tie $x, $m" and "chop".  These have all
	   been fixed.

       o   A 5.10.0 optimisation to clear the temporary stack within the implicit loop of
	   "s///ge" has been reverted, as it turned out to be the cause of obscure bugs in
	   seemingly unrelated parts of the interpreter [commit ef0d4e17921ee3de].

       o   The line numbers for warnings inside "elsif" are now correct.

       o   The ".." operator now works correctly with ranges whose ends are at or close to the
	   values of the smallest and largest integers.

       o   "binmode STDIN, ':raw'" could lead to segmentation faults on some platforms.  This has
	   been fixed [RT #54828].

       o   An off-by-one error meant that "index $str, ..." was effectively being executed as
	   "index "$str\0", ...". This has been fixed [RT #53746].

       o   Various leaks associated with named captures in regexes have been fixed [RT #57024].

       o   A weak reference to a hash would leak. This was affecting "DBI" [RT #56908].

       o   Using (?|) in a regex could cause a segfault [RT #59734].

       o   Use of a UTF-8 "tr//" within a closure could cause a segfault [RT #61520].

       o   Calling "Perl_sv_chop()" or otherwise upgrading an SV could result in an unaligned
	   64-bit access on the SPARC architecture [RT #60574].

       o   In the 5.10.0 release, "inc_version_list" would incorrectly list "5.10.*" after
	   "5.8.*"; this affected the @INC search order [RT #67628].

       o   In 5.10.0, "pack "a*", $tainted_value" returned a non-tainted value [RT #52552].

       o   In 5.10.0, "printf" and "sprintf" could produce the fatal error "panic:
	   utf8_mg_pos_cache_update" when printing UTF-8 strings [RT #62666].

       o   In the 5.10.0 release, a dynamically created "AUTOLOAD" method might be missed (method
	   cache issue) [RT #60220,60232].

       o   In the 5.10.0 release, a combination of "use feature" and "//ee" could cause a memory
	   leak [RT #63110].

       o   "-C" on the shebang ("#!") line is once more permitted if it is also specified on the
	   command line. "-C" on the shebang line used to be a silent no-op if it was not also on
	   the command line, so perl 5.10.0 disallowed it, which broke some scripts. Now perl
	   checks whether it is also on the command line and only dies if it is not [RT #67880].

       o   In 5.10.0, certain types of re-entrant regular expression could crash, or cause the
	   following assertion failure [RT #60508]:

	       Assertion rx->sublen >= (s - rx->subbeg) + i failed

       o   Perl now includes previously missing files from the Unicode Character Database.

       o   Perl now honors "TMPDIR" when opening an anonymous temporary file.

Platform Specific Changes
       Perl is incredibly portable. In general, if a platform has a C compiler, someone has
       ported Perl to it (or will soon).  We're happy to announce that Perl 5.12 includes support
       for several new platforms.  At the same time, it's time to bid farewell to some (very) old
       friends.

   New Platforms
       Haiku
	   Perl's developers have merged patches from Haiku's maintainers. Perl should now build
	   on Haiku.

       MirOS BSD
	   Perl should now build on MirOS BSD.

   Discontinued Platforms
       Domain/OS
       MiNT
       Tenon MachTen

   Updated Platforms
       AIX
	   o   Removed libbsd for AIX 5L and 6.1. Only "flock()" was used from libbsd.

	   o   Removed libgdbm for AIX 5L and 6.1 if libgdbm < 1.8.3-5 is installed.  The libgdbm
	       is delivered as an optional package with the AIX Toolbox.  Unfortunately the
	       versions below 1.8.3-5 are broken.

	   o   Hints changes mean that AIX 4.2 should work again.

       Cygwin
	   o   Perl now supports IPv6 on Cygwin 1.7 and newer.

	   o   On Cygwin we now strip the last number from the DLL. This has been the behaviour
	       in the cygwin.com build for years. The hints files have been updated.

       Darwin (Mac OS X)
	   o   Skip testing the be_BY.CP1131 locale on Darwin 10 (Mac OS X 10.6), as it's still
	       buggy.

	   o   Correct infelicities in the regexp used to identify buggy locales on Darwin 8 and
	       9 (Mac OS X 10.4 and 10.5, respectively).

       DragonFly BSD
	   o   Fix thread library selection [perl #69686]

       FreeBSD
	   o   The hints files now identify the correct threading libraries on FreeBSD 7 and
	       later.

       Irix
	   o   We now work around a bizarre preprocessor bug in the Irix 6.5 compiler: "cc -E -"
	       unfortunately goes into K&R mode, but "cc -E file.c" doesn't.

       NetBSD
	   o   Hints now supports versions 5.*.

       OpenVMS
	   o   "-UDEBUGGING" is now the default on VMS.

	       Like it has been everywhere else for ages and ages. Also make command-line
	       selection of -UDEBUGGING and -DDEBUGGING work in configure.com; before the only
	       way to turn it off was by saying no in answer to the interactive question.

	   o   The default pipe buffer size on VMS has been updated to 8192 on 64-bit systems.

	   o   Reads from the in-memory temporary files of "PerlIO::scalar" used to fail if $/
	       was set to a numeric reference (to indicate record-style reads).  This is now
	       fixed.

	   o   VMS now supports "getgrgid".

	   o   Many improvements and cleanups have been made to the VMS file name handling and
	       conversion code.

	   o   Enabling the "PERL_VMS_POSIX_EXIT" logical name now encodes a POSIX exit status in
	       a VMS condition value for better interaction with GNV's bash shell and other
	       utilities that depend on POSIX exit values. See "$?" in perlvms for details.

	   o   "File::Copy" now detects Unix compatibility mode on VMS.

       Stratus VOS
	   o   Various changes from Stratus have been merged in.

       Symbian
	   o   There is now support for Symbian S60 3.2 SDK and S60 5.0 SDK.

       Windows
	   o   Perl 5.12 supports Windows 2000 and later. The supporting code for legacy versions
	       of Windows is still included, but will be removed during the next development
	       cycle.

	   o   Initial support for building Perl with MinGW-w64 is now available.

	   o   perl.exe now includes a manifest resource to specify the "trustInfo" settings for
	       Windows Vista and later. Without this setting Windows would treat perl.exe as a
	       legacy application and apply various heuristics like redirecting access to
	       protected file system areas (like the "Program Files" folder) to the users
	       "VirtualStore" instead of generating a proper "permission denied" error.

	       The manifest resource also requests the Microsoft Common-Controls version 6.0
	       (themed controls introduced in Windows XP).  Check out the Win32::VisualStyles
	       module on CPAN to switch back to old style unthemed controls for legacy
	       applications.

	   o   The "-t" filetest operator now only returns true if the filehandle is connected to
	       a console window.  In previous versions of Perl it would return true for all
	       character mode devices, including NUL and LPT1.

	   o   The "-p" filetest operator now works correctly, and the Fcntl::S_IFIFO constant is
	       defined when Perl is compiled with Microsoft Visual C.  In previous Perl versions
	       "-p" always returned a false value, and the Fcntl::S_IFIFO constant was not
	       defined.

	       This bug is specific to Microsoft Visual C and never affected Perl binaries built
	       with MinGW.

	   o   The socket error codes are now more widely supported:  The POSIX module will
	       define the symbolic names, like POSIX::EWOULDBLOCK, and stringification of socket
	       error codes in $! works as well now;

		 C:\>perl -MPOSIX -E "$!=POSIX::EWOULDBLOCK; say $!"
		 A non-blocking socket operation could not be completed immediately.

	   o   flock() will now set sensible error codes in $!.  Previous Perl versions copied
	       the value of $^E into $!, which caused much confusion.

	   o   select() now supports all empty "fd_set"s more correctly.

	   o   '.\foo' and '..\foo'  were treated differently than './foo' and '../foo' by "do"
	       and "require" [RT #63492].

	   o   Improved message window handling means that "alarm" and "kill" messages will no
	       longer be dropped under race conditions.

	   o   Various bits of Perl's build infrastructure are no longer converted to win32 line
	       endings at release time. If this hurts you, please report the problem with the
	       perlbug program included with perl.

Known Problems
       This is a list of some significant unfixed bugs, which are regressions from either 5.10.x
       or 5.8.x.

       o   Some CPANPLUS tests may fail if there is a functioning file ../../cpanp-run-perl
	   outside your build directory. The failure shouldn't imply there's a problem with the
	   actual functional software. The bug is already fixed in [RT #74188] and is scheduled
	   for inclusion in perl-v5.12.1.

       o   "List::Util::first" misbehaves in the presence of a lexical $_ (typically introduced
	   by "my $_" or implicitly by "given"). The variable which gets set for each iteration
	   is the package variable $_, not the lexical $_ [RT #67694].

	   A similar issue may occur in other modules that provide functions which take a block
	   as their first argument, like

	       foo { ... $_ ...} list

       o   Some regexes may run much more slowly when run in a child thread compared with the
	   thread the pattern was compiled into [RT #55600].

       o   Things like ""\N{LATIN SMALL LIGATURE FF}" =~ /\N{LATIN SMALL LETTER F}+/" will appear
	   to hang as they get into a very long running loop [RT #72998].

       o   Several porters have reported mysterious crashes when Perl's entire test suite is run
	   after a build on certain Windows 2000 systems. When run by hand, the individual tests
	   reportedly work fine.

Errata
       o   This one is actually a change introduced in 5.10.0, but it was missed from that
	   release's perldelta, so it is mentioned here instead.

	   A bugfix related to the handling of the "/m" modifier and "qr" resulted in a change of
	   behaviour between 5.8.x and 5.10.0:

	       # matches in 5.8.x, doesn't match in 5.10.0
	       $re = qr/^bar/; "foo\nbar" =~ /$re/m;

Acknowledgements
       Perl 5.12.0 represents approximately two years of development since Perl 5.10.0 and
       contains over 750,000 lines of changes across over 3,000 files from over 200 authors and
       committers.

       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 5.12.0:

       Aaron Crane, Abe Timmerman, Abhijit Menon-Sen, Abigail, Adam Russell, Adriano Ferreira,
       var Arnfjoer` Bjarmason, Alan Grover, Alexandr Ciornii, Alex Davies, Alex Vandiver,
       Andreas Koenig, Andrew Rodland, andrew@sundale.net, Andy Armstrong, Andy Dougherty, Jose
       AUGUSTE-ETIENNE, Benjamin Smith, Ben Morrow, bharanee rathna, Bo Borgerson, Bo Lindbergh,
       Brad Gilbert, Bram, Brendan O'Dea, brian d foy, Charles Bailey, Chip Salzenberg, Chris
       'BinGOs' Williams, Christoph Lamprecht, Chris Williams, chromatic, Claes Jakobsson, Craig
       A. Berry, Dan Dascalescu, Daniel Frederick Crisman, Daniel M. Quinlan, Dan Jacobson, Dan
       Kogai, Dave Mitchell, Dave Rolsky, David Cantrell, David Dick, David Golden, David
       Mitchell, David M. Syzdek, David Nicol, David Wheeler, Dennis Kaarsemaker, Dintelmann,
       Peter, Dominic Dunlop, Dr.Ruud, Duke Leto, Enrico Sorcinelli, Eric Brine, Father
       Chrysostomos, Florian Ragwitz, Frank Wiegand, Gabor Szabo, Gene Sullivan, Geoffrey T.
       Dairiki, George Greer, Gerard Goossen, Gisle Aas, Goro Fuji, Graham Barr, Green, Paul,
       Hans Dieter Pearcey, Harmen, H. Merijn Brand, Hugo van der Sanden, Ian Goodacre, Igor
       Sutton, Ingo Weinhold, James Bence, James Mastros, Jan Dubois, Jari Aalto, Jarkko
       Hietaniemi, Jay Hannah, Jerry Hedden, Jesse Vincent, Jim Cromie, Jody Belka, John E.
       Malmberg, John Malmberg, John Peacock, John Peacock via RT, John P. Linderman, John
       Wright, Josh ben Jore, Jos I. Boumans, Karl Williamson, Kenichi Ishigaki, Ken Williams,
       Kevin Brintnall, Kevin Ryde, Kurt Starsinic, Leon Brocard, Lubomir Rintel, Luke Ross,
       Marcel Gruenauer, Marcus Holland-Moritz, Mark Jason Dominus, Marko Asplund, Martin Hasch,
       Mashrab Kuvatov, Matt Kraai, Matt S Trout, Max Maischein, Michael Breen, Michael Cartmell,
       Michael G Schwern, Michael Witten, Mike Giroux, Milosz Tanski, Moritz Lenz, Nicholas
       Clark, Nick Cleaton, Niko Tyni, Offer Kaye, Osvaldo Villalon, Paul Fenwick, Paul Gaborit,
       Paul Green, Paul Johnson, Paul Marquess, Philip Hazel, Philippe Bruhat, Rafael Garcia-
       Suarez, Rainer Tammer, Rajesh Mandalemula, Reini Urban, Renee Baecker, Ricardo Signes,
       Ricardo SIGNES, Richard Foley, Rich Rauenzahn, Rick Delaney, Risto Kankkunen, Robert May,
       Roberto C. Sanchez, Robin Barker, SADAHIRO Tomoyuki, Salvador Ortiz Garcia, Sam Vilain,
       Scott Lanning, Sebastien Aperghis-Tramoni, Sergio Durigan Junior, Shlomi Fish, Simon
       'corecode' Schubert, Sisyphus, Slaven Rezic, Smylers, Steffen Mueller, Steffen Ullrich,
       Stepan Kasal, Steve Hay, Steven Schubiger, Steve Peters, Tels, The Doctor, Tim Bunce, Tim
       Jenness, Todd Rinaldo, Tom Christiansen, Tom Hukins, Tom Wyant, Tony Cook, Torsten
       Schoenfeld, Tye McQueen, Vadim Konovalov, Vincent Pit, Hio YAMASHINA, Yasuhiro Matsumoto,
       Yitzchak Scott-Thoennes, Yuval Kogman, Yves Orton, Zefram, Zsban Ambrus

       This is woefully incomplete as it's automatically generated from version control history.
       In particular, it doesn't include the names of the (very much appreciated) contributors
       who reported issues in previous versions of Perl that helped make Perl 5.12.0 better. For
       a more complete list of all of Perl's historical contributors, please see the "AUTHORS"
       file in the Perl 5.12.0 distribution.

       Our "retired" pumpkings Nicholas Clark and Rafael Garcia-Suarez deserve special thanks for
       their brilliant and substantive ongoing contributions. Nicholas personally authored over
       30% of the patches since 5.10.0. Rafael comes in second in patch authorship with 11%, but
       is first by a long shot in committing patches authored by others, pushing 44% of the
       commits since 5.10.0 in this category, often after providing considerable coaching to the
       patch authors. These statistics in no way comprise all of their contributions, but express
       in shorthand that we couldn't have done it without them.

       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.

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
       analyzed 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 the 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 only
       use this address for security issues in the Perl core, not for modules independently
       distributed on CPAN.

SEE ALSO
       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.

       <http://dev.perl.org/perl5/errata.html> for a list of issues found after this release, as
       well as a list of CPAN modules known to be incompatible with this release.

perl v5.16.3				    2013-03-04				 PERL5120DELTA(1)
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