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CentOS 7.0 - man page for perl581delta (centos section 1)

PERL581DELTA(1) 		 Perl Programmers Reference Guide		  PERL581DELTA(1)

NAME
       perl581delta - what is new for perl v5.8.1

DESCRIPTION
       This document describes differences between the 5.8.0 release and the 5.8.1 release.

       If you are upgrading from an earlier release such as 5.6.1, first read the perl58delta,
       which describes differences between 5.6.0 and 5.8.0.

       In case you are wondering about 5.6.1, it was bug-fix-wise rather identical to the
       development release 5.7.1.  Confused?  This timeline hopefully helps a bit: it lists the
       new major releases, their maintenance releases, and the development releases.

		 New	 Maintenance  Development

		 5.6.0				   2000-Mar-22
				      5.7.0	   2000-Sep-02
			 5.6.1			   2001-Apr-08
				      5.7.1	   2001-Apr-09
				      5.7.2	   2001-Jul-13
				      5.7.3	   2002-Mar-05
		 5.8.0				   2002-Jul-18
			 5.8.1			   2003-Sep-25

Incompatible Changes
   Hash Randomisation
       Mainly due to security reasons, the "random ordering" of hashes has been made even more
       random.	Previously while the order of hash elements from keys(), values(), and each() was
       essentially random, it was still repeatable.  Now, however, the order varies between
       different runs of Perl.

       Perl has never guaranteed any ordering of the hash keys, and the ordering has already
       changed several times during the lifetime of Perl 5.  Also, the ordering of hash keys has
       always been, and continues to be, affected by the insertion order.

       The added randomness may affect applications.

       One possible scenario is when output of an application has included hash data.  For
       example, if you have used the Data::Dumper module to dump data into different files, and
       then compared the files to see whether the data has changed, now you will have false
       positives since the order in which hashes are dumped will vary.	In general the cure is to
       sort the keys (or the values); in particular for Data::Dumper to use the "Sortkeys"
       option.	If some particular order is really important, use tied hashes: for example the
       Tie::IxHash module which by default preserves the order in which the hash elements were
       added.

       More subtle problem is reliance on the order of "global destruction".  That is what
       happens at the end of execution: Perl destroys all data structures, including user data.
       If your destructors (the DESTROY subroutines) have assumed any particular ordering to the
       global destruction, there might be problems ahead.  For example, in a destructor of one
       object you cannot assume that objects of any other class are still available, unless you
       hold a reference to them.  If the environment variable PERL_DESTRUCT_LEVEL is set to a
       non-zero value, or if Perl is exiting a spawned thread, it will also destruct the ordinary
       references and the symbol tables that are no longer in use.  You can't call a class method
       or an ordinary function on a class that has been collected that way.

       The hash randomisation is certain to reveal hidden assumptions about some particular
       ordering of hash elements, and outright bugs: it revealed a few bugs in the Perl core and
       core modules.

       To disable the hash randomisation in runtime, set the environment variable PERL_HASH_SEED
       to 0 (zero) before running Perl (for more information see "PERL_HASH_SEED" in perlrun), or
       to disable the feature completely in compile time, compile with "-DNO_HASH_SEED" (see
       INSTALL).

       See "Algorithmic Complexity Attacks" in perlsec for the original rationale behind this
       change.

   UTF-8 On Filehandles No Longer Activated By Locale
       In Perl 5.8.0 all filehandles, including the standard filehandles, were implicitly set to
       be in Unicode UTF-8 if the locale settings indicated the use of UTF-8.  This feature
       caused too many problems, so the feature was turned off and redesigned: see "Core
       Enhancements".

   Single-number v-strings are no longer v-strings before "=>"
       The version strings or v-strings (see "Version Strings" in perldata) feature introduced in
       Perl 5.6.0 has been a source of some confusion-- especially when the user did not want to
       use it, but Perl thought it knew better.  Especially troublesome has been the feature that
       before a "=>" a version string (a "v" followed by digits) has been interpreted as a
       v-string instead of a string literal.  In other words:

	       %h = ( v65 => 42 );

       has meant since Perl 5.6.0

	       %h = ( 'A' => 42 );

       (at least in platforms of ASCII progeny)  Perl 5.8.1 restores the more natural
       interpretation

	       %h = ( 'v65' => 42 );

       The multi-number v-strings like v65.66 and 65.66.67 still continue to be v-strings in Perl
       5.8.

   (Win32) The -C Switch Has Been Repurposed
       The -C switch has changed in an incompatible way.  The old semantics of this switch only
       made sense in Win32 and only in the "use utf8" universe in 5.6.x releases, and do not make
       sense for the Unicode implementation in 5.8.0.  Since this switch could not have been used
       by anyone, it has been repurposed.  The behavior that this switch enabled in 5.6.x
       releases may be supported in a transparent, data-dependent fashion in a future release.

       For the new life of this switch, see "UTF-8 no longer default under UTF-8 locales", and
       "-C" in perlrun.

   (Win32) The /d Switch Of cmd.exe
       Perl 5.8.1 uses the /d switch when running the cmd.exe shell internally for system(),
       backticks, and when opening pipes to external programs.	The extra switch disables the
       execution of AutoRun commands from the registry, which is generally considered undesirable
       when running external programs.	If you wish to retain compatibility with the older
       behavior, set PERL5SHELL in your environment to "cmd /x/c".

Core Enhancements
   UTF-8 no longer default under UTF-8 locales
       In Perl 5.8.0 many Unicode features were introduced.   One of them was found to be of more
       nuisance than benefit: the automagic (and silent) "UTF-8-ification" of filehandles,
       including the standard filehandles, if the user's locale settings indicated use of UTF-8.

       For example, if you had "en_US.UTF-8" as your locale, your STDIN and STDOUT were
       automatically "UTF-8", in other words an implicit binmode(..., ":utf8") was made.  This
       meant that trying to print, say, chr(0xff), ended up printing the bytes 0xc3 0xbf.  Hardly
       what you had in mind unless you were aware of this feature of Perl 5.8.0.  The problem is
       that the vast majority of people weren't: for example in RedHat releases 8 and 9 the
       default locale setting is UTF-8, so all RedHat users got UTF-8 filehandles, whether they
       wanted it or not.  The pain was intensified by the Unicode implementation of Perl 5.8.0
       (still) having nasty bugs, especially related to the use of s/// and tr///.  (Bugs that
       have been fixed in 5.8.1)

       Therefore a decision was made to backtrack the feature and change it from implicit silent
       default to explicit conscious option.  The new Perl command line option "-C" and its
       counterpart environment variable PERL_UNICODE can now be used to control how Perl and
       Unicode interact at interfaces like I/O and for example the command line arguments.  See
       "-C" in perlrun and "PERL_UNICODE" in perlrun for more information.

   Unsafe signals again available
       In Perl 5.8.0 the so-called "safe signals" were introduced.  This means that Perl no
       longer handles signals immediately but instead "between opcodes", when it is safe to do
       so.  The earlier immediate handling easily could corrupt the internal state of Perl,
       resulting in mysterious crashes.

       However, the new safer model has its problems too.  Because now an opcode, a basic unit of
       Perl execution, is never interrupted but instead let to run to completion, certain
       operations that can take a long time now really do take a long time.  For example, certain
       network operations have their own blocking and timeout mechanisms, and being able to
       interrupt them immediately would be nice.

       Therefore perl 5.8.1 introduces a "backdoor" to restore the pre-5.8.0 (pre-5.7.3, really)
       signal behaviour.  Just set the environment variable PERL_SIGNALS to "unsafe", and the old
       immediate (and unsafe) signal handling behaviour returns.  See "PERL_SIGNALS" in perlrun
       and "Deferred Signals (Safe Signals)" in perlipc.

       In completely unrelated news, you can now use safe signals with POSIX::SigAction.  See
       "POSIX::SigAction" in POSIX.

   Tied Arrays with Negative Array Indices
       Formerly, the indices passed to "FETCH", "STORE", "EXISTS", and "DELETE" methods in tied
       array class were always non-negative.  If the actual argument was negative, Perl would
       call FETCHSIZE implicitly and add the result to the index before passing the result to the
       tied array method.  This behaviour is now optional.  If the tied array class contains a
       package variable named $NEGATIVE_INDICES which is set to a true value, negative values
       will be passed to "FETCH", "STORE", "EXISTS", and "DELETE" unchanged.

   local ${$x}
       The syntaxes

	       local ${$x}
	       local @{$x}
	       local %{$x}

       now do localise variables, given that the $x is a valid variable name.

   Unicode Character Database 4.0.0
       The copy of the Unicode Character Database included in Perl 5.8 has been updated to 4.0.0
       from 3.2.0.  This means for example that the Unicode character properties are as in
       Unicode 4.0.0.

   Deprecation Warnings
       There is one new feature deprecation.  Perl 5.8.0 forgot to add some deprecation warnings,
       these warnings have now been added.  Finally, a reminder of an impending feature removal.

       (Reminder) Pseudo-hashes are deprecated (really)

       Pseudo-hashes were deprecated in Perl 5.8.0 and will be removed in Perl 5.10.0, see
       perl58delta for details.  Each attempt to access pseudo-hashes will trigger the warning
       "Pseudo-hashes are deprecated".	If you really want to continue using pseudo-hashes but
       not to see the deprecation warnings, use:

	   no warnings 'deprecated';

       Or you can continue to use the fields pragma, but please don't expect the data structures
       to be pseudohashes any more.

       (Reminder) 5.005-style threads are deprecated (really)

       5.005-style threads (activated by "use Thread;") were deprecated in Perl 5.8.0 and will be
       removed after Perl 5.8, see perl58delta for details.  Each 5.005-style thread creation
       will trigger the warning "5.005 threads are deprecated".  If you really want to continue
       using the 5.005 threads but not to see the deprecation warnings, use:

	   no warnings 'deprecated';

       (Reminder) The $* variable is deprecated (really)

       The $* variable controlling multi-line matching has been deprecated and will be removed
       after 5.8.  The variable has been deprecated for a long time, and a deprecation warning
       "Use of $* is deprecated" is given, now the variable will just finally be removed.  The
       functionality has been supplanted by the "/s" and "/m" modifiers on pattern matching.  If
       you really want to continue using the $*-variable but not to see the deprecation warnings,
       use:

	   no warnings 'deprecated';

   Miscellaneous Enhancements
       "map" in void context is no longer expensive. "map" is now context aware, and will not
       construct a list if called in void context.

       If a socket gets closed by the server while printing to it, the client now gets a SIGPIPE.
       While this new feature was not planned, it fell naturally out of PerlIO changes, and is to
       be considered an accidental feature.

       PerlIO::get_layers(FH) returns the names of the PerlIO layers active on a filehandle.

       PerlIO::via layers can now have an optional UTF8 method to indicate whether the layer
       wants to "auto-:utf8" the stream.

       utf8::is_utf8() has been added as a quick way to test whether a scalar is encoded
       internally in UTF-8 (Unicode).

Modules and Pragmata
   Updated Modules And Pragmata
       The following modules and pragmata have been updated since Perl 5.8.0:

       base
       B::Bytecode
	   In much better shape than it used to be.  Still far from perfect, but maybe worth a
	   try.

       B::Concise
       B::Deparse
       Benchmark
	   An optional feature, ":hireswallclock", now allows for high resolution wall clock
	   times (uses Time::HiRes).

       ByteLoader
	   See B::Bytecode.

       bytes
	   Now has bytes::substr.

       CGI
       charnames
	   One can now have custom character name aliases.

       CPAN
	   There is now a simple command line frontend to the CPAN.pm module called cpan.

       Data::Dumper
	   A new option, Pair, allows choosing the separator between hash keys and values.

       DB_File
       Devel::PPPort
       Digest::MD5
       Encode
	   Significant updates on the encoding pragma functionality (tr/// and the DATA
	   filehandle, formats).

	   If a filehandle has been marked as to have an encoding, unmappable characters are
	   detected already during input, not later (when the corrupted data is being used).

	   The ISO 8859-6 conversion table has been corrected (the 0x30..0x39 erroneously mapped
	   to U+0660..U+0669, instead of U+0030..U+0039).  The GSM 03.38 conversion did not
	   handle escape sequences correctly.  The UTF-7 encoding has been added (making Encode
	   feature-complete with Unicode::String).

       fields
       libnet
       Math::BigInt
	   A lot of bugs have been fixed since v1.60, the version included in Perl v5.8.0.
	   Especially noteworthy are the bug in Calc that caused div and mod to fail for some
	   large values, and the fixes to the handling of bad inputs.

	   Some new features were added, e.g. the broot() method, you can now pass parameters to
	   config() to change some settings at runtime, and it is now possible to trap the
	   creation of NaN and infinity.

	   As usual, some optimizations took place and made the math overall a tad faster. In
	   some cases, quite a lot faster, actually. Especially alternative libraries like
	   Math::BigInt::GMP benefit from this. In addition, a lot of the quite clunky routines
	   like fsqrt() and flog() are now much much faster.

       MIME::Base64
       NEXT
	   Diamond inheritance now works.

       Net::Ping
       PerlIO::scalar
	   Reading from non-string scalars (like the special variables, see perlvar) now works.

       podlators
       Pod::LaTeX
       PodParsers
       Pod::Perldoc
	   Complete rewrite.  As a side-effect, no longer refuses to startup when run by root.

       Scalar::Util
	   New utilities: refaddr, isvstring, looks_like_number, set_prototype.

       Storable
	   Can now store code references (via B::Deparse, so not foolproof).

       strict
	   Earlier versions of the strict pragma did not check the parameters implicitly passed
	   to its "import" (use) and "unimport" (no) routine.  This caused the false idiom such
	   as:

		   use strict qw(@ISA);
		   @ISA = qw(Foo);

	   This however (probably) raised the false expectation that the strict refs, vars and
	   subs were being enforced (and that @ISA was somehow "declared").  But the strict refs,
	   vars, and subs are not enforced when using this false idiom.

	   Starting from Perl 5.8.1, the above will cause an error to be raised.  This may cause
	   programs which used to execute seemingly correctly without warnings and errors to fail
	   when run under 5.8.1.  This happens because

		   use strict qw(@ISA);

	   will now fail with the error:

		   Unknown 'strict' tag(s) '@ISA'

	   The remedy to this problem is to replace this code with the correct idiom:

		   use strict;
		   use vars qw(@ISA);
		   @ISA = qw(Foo);

       Term::ANSIcolor
       Test::Harness
	   Now much more picky about extra or missing output from test scripts.

       Test::More
       Test::Simple
       Text::Balanced
       Time::HiRes
	   Use of nanosleep(), if available, allows mixing subsecond sleeps with alarms.

       threads
	   Several fixes, for example for join() problems and memory leaks.  In some platforms
	   (like Linux) that use glibc the minimum memory footprint of one ithread has been
	   reduced by several hundred kilobytes.

       threads::shared
	   Many memory leaks have been fixed.

       Unicode::Collate
       Unicode::Normalize
       Win32::GetFolderPath
       Win32::GetOSVersion
	   Now returns extra information.

Utility Changes
       The "h2xs" utility now produces a more modern layout: Foo-Bar/lib/Foo/Bar.pm instead of
       Foo/Bar/Bar.pm.	Also, the boilerplate test is now called t/Foo-Bar.t instead of t/1.t.

       The Perl debugger (lib/perl5db.pl) has now been extensively documented and bugs found
       while documenting have been fixed.

       "perldoc" has been rewritten from scratch to be more robust and feature rich.

       "perlcc -B" works now at least somewhat better, while "perlcc -c" is rather more broken.
       (The Perl compiler suite as a whole continues to be experimental.)

New Documentation
       perl573delta has been added to list the differences between the (now quite obsolete)
       development releases 5.7.2 and 5.7.3.

       perl58delta has been added: it is the perldelta of 5.8.0, detailing the differences
       between 5.6.0 and 5.8.0.

       perlartistic has been added: it is the Artistic License in pod format, making it easier
       for modules to refer to it.

       perlcheat has been added: it is a Perl cheat sheet.

       perlgpl has been added: it is the GNU General Public License in pod format, making it
       easier for modules to refer to it.

       perlmacosx has been added to tell about the installation and use of Perl in Mac OS X.

       perlos400 has been added to tell about the installation and use of Perl in OS/400 PASE.

       perlreref has been added: it is a regular expressions quick reference.

Installation and Configuration Improvements
       The Unix standard Perl location, /usr/bin/perl, is no longer overwritten by default if it
       exists.	This change was very prudent because so many Unix vendors already provide a
       /usr/bin/perl, but simultaneously many system utilities may depend on that exact version
       of Perl, so better not to overwrite it.

       One can now specify installation directories for site and vendor man and HTML pages, and
       site and vendor scripts.  See INSTALL.

       One can now specify a destination directory for Perl installation by specifying the
       DESTDIR variable for "make install".  (This feature is slightly different from the
       previous "Configure -Dinstallprefix=...".)  See INSTALL.

       gcc versions 3.x introduced a new warning that caused a lot of noise during Perl
       compilation: "gcc -Ialreadyknowndirectory (warning: changing search order)".  This warning
       has now been avoided by Configure weeding out such directories before the compilation.

       One can now build subsets of Perl core modules by using the Configure flags
       "-Dnoextensions=..." and "-Donlyextensions=...", see INSTALL.

   Platform-specific enhancements
       In Cygwin Perl can now be built with threads ("Configure -Duseithreads").  This works with
       both Cygwin 1.3.22 and Cygwin 1.5.3.

       In newer FreeBSD releases Perl 5.8.0 compilation failed because of trying to use malloc.h,
       which in FreeBSD is just a dummy file, and a fatal error to even try to use.  Now malloc.h
       is not used.

       Perl is now known to build also in Hitachi HI-UXMPP.

       Perl is now known to build again in LynxOS.

       Mac OS X now installs with Perl version number embedded in installation directory names
       for easier upgrading of user-compiled Perl, and the installation directories in general
       are more standard.  In other words, the default installation no longer breaks the Apple-
       provided Perl.  On the other hand, with "Configure -Dprefix=/usr" you can now really
       replace the Apple-supplied Perl (please be careful).

       Mac OS X now builds Perl statically by default.	This change was done mainly for faster
       startup times.  The Apple-provided Perl is still dynamically linked and shared, and you
       can enable the sharedness for your own Perl builds by "Configure -Duseshrplib".

       Perl has been ported to IBM's OS/400 PASE environment.  The best way to build a Perl for
       PASE is to use an AIX host as a cross-compilation environment.  See README.os400.

       Yet another cross-compilation option has been added: now Perl builds on OpenZaurus, an
       Linux distribution based on Mandrake + Embedix for the Sharp Zaurus PDA.  See the
       Cross/README file.

       Tru64 when using gcc 3 drops the optimisation for toke.c to "-O2" because of gigantic
       memory use with the default "-O3".

       Tru64 can now build Perl with the newer Berkeley DBs.

       Building Perl on WinCE has been much enhanced, see README.ce and README.perlce.

Selected Bug Fixes
   Closures, eval and lexicals
       There have been many fixes in the area of anonymous subs, lexicals and closures.  Although
       this means that Perl is now more "correct", it is possible that some existing code will
       break that happens to rely on the faulty behaviour.  In practice this is unlikely unless
       your code contains a very complex nesting of anonymous subs, evals and lexicals.

   Generic fixes
       If an input filehandle is marked ":utf8" and Perl sees illegal UTF-8 coming in when doing
       "<FH>", if warnings are enabled a warning is immediately given - instead of being silent
       about it and Perl being unhappy about the broken data later.  (The ":encoding(utf8)" layer
       also works the same way.)

       binmode(SOCKET, ":utf8") only worked on the input side, not on the output side of the
       socket.	Now it works both ways.

       For threaded Perls certain system database functions like getpwent() and getgrent() now
       grow their result buffer dynamically, instead of failing.  This means that at sites with
       lots of users and groups the functions no longer fail by returning only partial results.

       Perl 5.8.0 had accidentally broken the capability for users to define their own
       uppercase<->lowercase Unicode mappings (as advertised by the Camel).  This feature has
       been fixed and is also documented better.

       In 5.8.0 this

	       $some_unicode .= <FH>;

       didn't work correctly but instead corrupted the data.  This has now been fixed.

       Tied methods like FETCH etc. may now safely access tied values, i.e.  resulting in a
       recursive call to FETCH etc.  Remember to break the recursion, though.

       At startup Perl blocks the SIGFPE signal away since there isn't much Perl can do about it.
       Previously this blocking was in effect also for programs executed from within Perl.  Now
       Perl restores the original SIGFPE handling routine, whatever it was, before running
       external programs.

       Linenumbers in Perl scripts may now be greater than 65536, or 2**16.  (Perl scripts have
       always been able to be larger than that, it's just that the linenumber for reported errors
       and warnings have "wrapped around".)  While scripts that large usually indicate a need to
       rethink your code a bit, such Perl scripts do exist, for example as results from generated
       code.  Now linenumbers can go all the way to 4294967296, or 2**32.

   Platform-specific fixes
       Linux

       o   Setting $0 works again (with certain limitations that Perl cannot do much about: see
	   "$0" in perlvar)

       HP-UX

       o   Setting $0 now works.

       VMS

       o   Configuration now tests for the presence of "poll()", and IO::Poll now uses the
	   vendor-supplied function if detected.

       o   A rare access violation at Perl start-up could occur if the Perl image was installed
	   with privileges or if there was an identifier with the subsystem attribute set in the
	   process's rightslist.  Either of these circumstances triggered tainting code that
	   contained a pointer bug.  The faulty pointer arithmetic has been fixed.

       o   The length limit on values (not keys) in the %ENV hash has been raised from 255 bytes
	   to 32640 bytes (except when the PERL_ENV_TABLES setting overrides the default use of
	   logical names for %ENV).  If it is necessary to access these long values from outside
	   Perl, be aware that they are implemented using search list logical names that store
	   the value in pieces, each 255-byte piece (up to 128 of them) being an element in the
	   search list. When doing a lookup in %ENV from within Perl, the elements are combined
	   into a single value.  The existing VMS-specific ability to access individual elements
	   of a search list logical name via the $ENV{'foo;N'} syntax (where N is the search list
	   index) is unimpaired.

       o   The piping implementation now uses local rather than global DCL symbols for inter-
	   process communication.

       o   File::Find could become confused when navigating to a relative directory whose name
	   collided with a logical name.  This problem has been corrected by adding directory
	   syntax to relative path names, thus preventing logical name translation.

       Win32

       o   A memory leak in the fork() emulation has been fixed.

       o   The return value of the ioctl() built-in function was accidentally broken in 5.8.0.
	   This has been corrected.

       o   The internal message loop executed by perl during blocking operations sometimes
	   interfered with messages that were external to Perl.  This often resulted in blocking
	   operations terminating prematurely or returning incorrect results, when Perl was
	   executing under environments that could generate Windows messages.  This has been
	   corrected.

       o   Pipes and sockets are now automatically in binary mode.

       o   The four-argument form of select() did not preserve $! (errno) properly when there
	   were errors in the underlying call.	This is now fixed.

       o   The "CR CR LF" problem of has been fixed, binmode(FH, ":crlf") is now effectively a
	   no-op.

New or Changed Diagnostics
       All the warnings related to pack() and unpack() were made more informative and consistent.

   Changed "A thread exited while %d threads were running"
       The old version

	   A thread exited while %d other threads were still running

       was misleading because the "other" included also the thread giving the warning.

   Removed "Attempt to clear a restricted hash"
       It is not illegal to clear a restricted hash, so the warning was removed.

   New "Illegal declaration of anonymous subroutine"
       You must specify the block of code for "sub".

   Changed "Invalid range "%s" in transliteration operator"
       The old version

	   Invalid [] range "%s" in transliteration operator

       was simply wrong because there are no "[] ranges" in tr///.

   New "Missing control char name in \c"
       Self-explanatory.

   New "Newline in left-justified string for %s"
       The padding spaces would appear after the newline, which is probably not what you had in
       mind.

   New "Possible precedence problem on bitwise %c operator"
       If you think this

	   $x & $y == 0

       tests whether the bitwise AND of $x and $y is zero, you will like this warning.

   New "Pseudo-hashes are deprecated"
       This warning should have been already in 5.8.0, since they are.

   New "read() on %s filehandle %s"
       You cannot read() (or sysread()) from a closed or unopened filehandle.

   New "5.005 threads are deprecated"
       This warning should have been already in 5.8.0, since they are.

   New "Tied variable freed while still in use"
       Something pulled the plug on a live tied variable, Perl plays safe by bailing out.

   New "To%s: illegal mapping '%s'"
       An illegal user-defined Unicode casemapping was specified.

   New "Use of freed value in iteration"
       Something modified the values being iterated over.  This is not good.

Changed Internals
       These news matter to you only if you either write XS code or like to know about or hack
       Perl internals (using Devel::Peek or any of the "B::" modules counts), or like to run Perl
       with the "-D" option.

       The embedding examples of perlembed have been reviewed to be up to date and consistent:
       for example, the correct use of PERL_SYS_INIT3() and PERL_SYS_TERM().

       Extensive reworking of the pad code (the code responsible for lexical variables) has been
       conducted by Dave Mitchell.

       Extensive work on the v-strings by John Peacock.

       UTF-8 length and position cache: to speed up the handling of Unicode (UTF-8) scalars, a
       cache was introduced.  Potential problems exist if an extension bypasses the official APIs
       and directly modifies the PV of an SV: the UTF-8 cache does not get cleared as it should.

       APIs obsoleted in Perl 5.8.0, like sv_2pv, sv_catpvn, sv_catsv, sv_setsv, are again
       available.

       Certain Perl core C APIs like cxinc and regatom are no longer available at all to code
       outside the Perl core of the Perl core extensions.  This is intentional.  They never
       should have been available with the shorter names, and if you application depends on them,
       you should (be ashamed and) contact perl5-porters to discuss what are the proper APIs.

       Certain Perl core C APIs like "Perl_list" are no longer available without their "Perl_"
       prefix.	If your XS module stops working because some functions cannot be found, in many
       cases a simple fix is to add the "Perl_" prefix to the function and the thread context
       "aTHX_" as the first argument of the function call.  This is also how it should always
       have been done: letting the Perl_-less forms to leak from the core was an accident.  For
       cleaner embedding you can also force this for all APIs by defining at compile time the cpp
       define PERL_NO_SHORT_NAMES.

       Perl_save_bool() has been added.

       Regexp objects (those created with "qr") now have S-magic rather than R-magic.  This fixed
       regexps of the form /...(??{...;$x})/ to no longer ignore changes made to $x.  The S-magic
       avoids dropping the caching optimization and making (??{...}) constructs obscenely slow
       (and consequently useless).  See also "Magic Variables" in perlguts.  Regexp::Copy was
       affected by this change.

       The Perl internal debugging macros DEBUG() and DEB() have been renamed to PERL_DEBUG() and
       PERL_DEB() to avoid namespace conflicts.

       "-DL" removed (the leaktest had been broken and unsupported for years, use alternative
       debugging mallocs or tools like valgrind and Purify).

       Verbose modifier "v" added for "-DXv" and "-Dsv", see perlrun.

New Tests
       In Perl 5.8.0 there were about 69000 separate tests in about 700 test files, in Perl 5.8.1
       there are about 77000 separate tests in about 780 test files.  The exact numbers depend on
       the Perl configuration and on the operating system platform.

Known Problems
       The hash randomisation mentioned in "Incompatible Changes" is definitely problematic: it
       will wake dormant bugs and shake out bad assumptions.

       If you want to use mod_perl 2.x with Perl 5.8.1, you will need mod_perl-1.99_10 or higher.
       Earlier versions of mod_perl 2.x do not work with the randomised hashes.  (mod_perl 1.x
       works fine.)  You will also need Apache::Test 1.04 or higher.

       Many of the rarer platforms that worked 100% or pretty close to it with perl 5.8.0 have
       been left a little bit untended since their maintainers have been otherwise busy lately,
       and therefore there will be more failures on those platforms.  Such platforms include Mac
       OS Classic, IBM z/OS (and other EBCDIC platforms), and NetWare.	The most common Perl
       platforms (Unix and Unix-like, Microsoft platforms, and VMS) have large enough testing and
       expert population that they are doing well.

   Tied hashes in scalar context
       Tied hashes do not currently return anything useful in scalar context, for example when
       used as boolean tests:

	       if (%tied_hash) { ... }

       The current nonsensical behaviour is always to return false, regardless of whether the
       hash is empty or has elements.

       The root cause is that there is no interface for the implementors of tied hashes to
       implement the behaviour of a hash in scalar context.

   Net::Ping 450_service and 510_ping_udp failures
       The subtests 9 and 18 of lib/Net/Ping/t/450_service.t, and the subtest 2 of
       lib/Net/Ping/t/510_ping_udp.t might fail if you have an unusual networking setup.  For
       example in the latter case the test is trying to send a UDP ping to the IP address
       127.0.0.1.

   B::C
       The C-generating compiler backend B::C (the frontend being "perlcc -c") is even more
       broken than it used to be because of the extensive lexical variable changes.  (The good
       news is that B::Bytecode and ByteLoader are better than they used to be.)

Platform Specific Problems
   EBCDIC Platforms
       IBM z/OS and other EBCDIC platforms continue to be problematic regarding Unicode support.
       Many Unicode tests are skipped when they really should be fixed.

   Cygwin 1.5 problems
       In Cygwin 1.5 the io/tell and op/sysio tests have failures for some yet unknown reason.
       In 1.5.5 the threads tests stress_cv, stress_re, and stress_string are failing unless the
       environment variable PERLIO is set to "perlio" (which makes also the io/tell failure go
       away).

       Perl 5.8.1 does build and work well with Cygwin 1.3: with (uname -a) "CYGWIN_NT-5.0 ...
       1.3.22(0.78/3/2) 2003-03-18 09:20 i686 ..."  a 100% "make test"	was achieved with
       "Configure -des -Duseithreads".

   HP-UX: HP cc warnings about sendfile and sendpath
       With certain HP C compiler releases (e.g. B.11.11.02) you will get many warnings like this
       (lines wrapped for easier reading):

	 cc: "/usr/include/sys/socket.h", line 504: warning 562:
	   Redeclaration of "sendfile" with a different storage class specifier:
	     "sendfile" will have internal linkage.
	 cc: "/usr/include/sys/socket.h", line 505: warning 562:
	   Redeclaration of "sendpath" with a different storage class specifier:
	     "sendpath" will have internal linkage.

       The warnings show up both during the build of Perl and during certain lib/ExtUtils tests
       that invoke the C compiler.  The warning, however, is not serious and can be ignored.

   IRIX: t/uni/tr_7jis.t falsely failing
       The test t/uni/tr_7jis.t is known to report failure under 'make test' or the test harness
       with certain releases of IRIX (at least IRIX 6.5 and MIPSpro Compilers Version 7.3.1.1m),
       but if run manually the test fully passes.

   Mac OS X: no usemymalloc
       The Perl malloc ("-Dusemymalloc") does not work at all in Mac OS X.  This is not that
       serious, though, since the native malloc works just fine.

   Tru64: No threaded builds with GNU cc (gcc)
       In the latest Tru64 releases (e.g. v5.1B or later) gcc cannot be used to compile a
       threaded Perl (-Duseithreads) because the system "<pthread.h>" file doesn't know about
       gcc.

   Win32: sysopen, sysread, syswrite
       As of the 5.8.0 release, sysopen()/sysread()/syswrite() do not behave like they used to in
       5.6.1 and earlier with respect to "text" mode.  These built-ins now always operate in
       "binary" mode (even if sysopen() was passed the O_TEXT flag, or if binmode() was used on
       the file handle).  Note that this issue should only make a difference for disk files, as
       sockets and pipes have always been in "binary" mode in the Windows port.  As this behavior
       is currently considered a bug, compatible behavior may be re-introduced in a future
       release.  Until then, the use of sysopen(), sysread() and syswrite() is not supported for
       "text" mode operations.

Future Directions
       The following things might happen in future.  The first publicly available releases having
       these characteristics will be the developer releases Perl 5.9.x, culminating in the Perl
       5.10.0 release.	These are our best guesses at the moment: we reserve the right to
       rethink.

       o   PerlIO will become The Default.  Currently (in Perl 5.8.x) the stdio library is still
	   used if Perl thinks it can use certain tricks to make stdio go really fast.	For
	   future releases our goal is to make PerlIO go even faster.

       o   A new feature called assertions will be available.  This means that one can have code
	   called assertions sprinkled in the code: usually they are optimised away, but they can
	   be enabled with the "-A" option.

       o   A new operator "//" (defined-or) will be available.	This means that one will be able
	   to say

	       $a // $b

	   instead of

	      defined $a ? $a : $b

	   and

	      $c //= $d;

	   instead of

	      $c = $d unless defined $c;

	   The operator will have the same precedence and associativity as "||".  A source code
	   patch against the Perl 5.8.1 sources will be available in CPAN as
	   authors/id/H/HM/HMBRAND/dor-5.8.1.diff.

       o   "unpack()" will default to unpacking the $_.

       o   Various Copy-On-Write techniques will be investigated in hopes of speeding up Perl.

       o   CPANPLUS, Inline, and Module::Build will become core modules.

       o   The ability to write true lexically scoped pragmas will be introduced.

       o   Work will continue on the bytecompiler and byteloader.

       o   v-strings as they currently exist are scheduled to be deprecated.  The v-less form
	   (1.2.3) will become a "version object" when used with "use", "require", and $VERSION.
	   $^V will also be a "version object" so the printf("%vd",...) construct will no longer
	   be needed.  The v-ful version (v1.2.3) will become obsolete.  The equivalence of
	   strings and v-strings (e.g.	that currently 5.8.0 is equal to "\5\8\0") will go away.
	   There may be no deprecation warning for v-strings, though: it is quite hard to detect
	   when v-strings are being used safely, and when they are not.

       o   5.005 Threads Will Be Removed

       o   The $* Variable Will Be Removed (it was deprecated a long time ago)

       o   Pseudohashes Will Be Removed

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://bugs.perl.org/ .  There
       may also be information at http://www.perl.com/ , the Perl Home Page.

       If you believe you have an unreported bug, please run the perlbug program included with
       your release.  Be sure to trim your bug down to a tiny but sufficient test case.  Your bug
       report, along with the output of "perl -V", will be sent off to perlbug@perl.org to be
       analysed by the Perl porting team.  You can browse and search the Perl 5 bugs at
       http://bugs.perl.org/

SEE ALSO
       The Changes file for exhaustive details on what changed.

       The INSTALL file for how to build Perl.

       The README file for general stuff.

       The Artistic and Copying files for copyright information.

perl v5.16.3				    2013-02-26				  PERL581DELTA(1)


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