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PERL5110DELTA(1)                      Perl Programmers Reference Guide                      PERL5110DELTA(1)



NAME
       perl5110delta - what is new for perl v5.11.0

DESCRIPTION
       This document describes differences between the 5.10.0 release and the 5.11.0 development release.

Incompatible Changes
   Unicode interpretation of \w, \d, \s, and the POSIX character classes redefined.
       Previous versions of Perl tried to map POSIX style character class definitions onto Unicode property
       names so that patterns would "dwim" when matches were made against latin-1 or unicode strings. This
       proved to be a mistake, breaking character class negation, causing forward compatibility problems (as
       Unicode keeps updating their property definitions and adding new characters), and other problems.

       Therefore we have now defined a new set of artificial "unicode" property names which will be used to
       do unicode matching of patterns using POSIX style character classes and perl short-form escape
       character classes like \w and \d.

       The key change here is that \d will no longer match every digit in the unicode standard (there are
       thousands) nor will \w match every word character in the standard, instead they will match precisely
       their POSIX or Perl definition.

       Those needing to match based on Unicode properties can continue to do so by using the \p{} syntax to
       match whichever property they like, including the new artificial definitions.

       NOTE: This is a backwards incompatible no-warning change in behaviour. If you are upgrading and you
       process large volumes of text look for POSIX and Perl style character classes and change them to the
       relevent property name (by removing the word 'Posix' from the current name).

       The following table maps the POSIX character class names, the escapes and the old and new Unicode
       property mappings:

           POSIX  Esc  Class               New-Property  ! Old-Property
           ----------------------------------------------+-------------alnum ----------------------------------------------+------------alnum
           alnum       [0-9A-Za-z]         IsPosixAlnum  ! IsAlnum
           alpha       [A-Za-z]            IsPosixAlpha  ! IsAlpha
           ascii       [\000-\177]         IsASCII       = IsASCII
           blank       [\011 ]             IsPosixBlank  !
           cntrl       [\0-\37\177]        IsPosixCntrl  ! IsCntrl
           digit   \d  [0-9]               IsPosixDigit  ! IsDigit
           graph       [!-~]               IsPosixGraph  ! IsGraph
           lower       [a-z]               IsPosixLower  ! IsLower
           print       [ -~]               IsPosixPrint  ! IsPrint
           punct       [!-/:-@[-`{-~]      IsPosixPunct  ! IsPunct
           space       [\11-\15 ]          IsPosixSpace  ! IsSpace
                   \s  [\11\12\14\15 ]     IsPerlSpace   ! IsSpacePerl
           upper       [A-Z]               IsPosixUpper  ! IsUpper
           word    \w  [0-9A-Z_a-z]        IsPerlWord    ! IsWord
           xdigit      [0-9A-Fa-f]         IsXDigit      = IsXDigit

       If you wish to build perl with the old mapping you may do so by setting

               #define PERL_LEGACY_UNICODE_CHARCLASS_MAPPINGS 1

       in regcomp.h, and then setting

               PERL_TEST_LEGACY_POSIX_CC

       to true your enviornment when testing.

   @INC reorganization
       In @INC, ARCHLIB and PRIVLIB now occur after after the current version's site_perl and vendor_perl.

   Switch statement changes
       The handling of complex expressions by the "given"/"when" switch statement has been enhanced. 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)".)

       The next section details more changes brought to the semantics to the smart match operator, that
       naturally also modify the behaviour of the switch statements where smart matching is implicitly used.
       These changers were also made for the 5.10.1 release, and will remain in subsequent 5.10 releases.

   Smart match changes
       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:

       •   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).

       •   "%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.

       •   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.

       •   "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).

       •   "$scalar ~~ @array" now always distributes the smart match across the elements of the array. It's
           true if one element in @array verifies "$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.)

   Labels can't be keywords
       Labels used as targets for the "goto", "last", "next" or "redo" statements cannot be keywords
       anymore. This restriction will prevent potential confusion between the "goto LABEL" and "goto EXPR"
       syntaxes: for example, a statement like "goto print" would jump to a label whose name would be the
       return value of "print()", (usually 1), instead of a label named "print". Moreover, the other control
       flow statements would just ignore any keyword passed to them as a label name. Since such labels
       cannot be defined anymore, this kind of error will be avoided.

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

       •   It is now a run-time error to use the smart match operator "~~" with an object that has no
           overload defined for it. (This way "~~" will not break encapsulation by matching against the
           object's internal representation as a reference.)

       •   The version control system used for the development of the perl interpreter has been switched
           from Perforce to git.  This is mainly an internal issue that only affects people actively working
           on the perl core; but it may have minor external visibility, for example in some of details of
           the output of "perl -V". See perlrepository for more information.

       •   The internal structure of the "ext/" directory in the perl source has been reorganised. In
           general, a module "Foo::Bar" whose source was stored under ext/Foo/Bar/ is now located under
           ext/Foo-Bar/. Also, nearly all dual-life modules have been moved from lib/ to ext/. This is
           purely a source tarball change, and should make no difference to the compilation or installation
           of perl, unless you have a very customised build process that explicitly relies on this
           structure, or which hard-codes the "nonxs_ext" Configure parameter. Specifically, this change
           does not by default alter the location of any files in the final installation.

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

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

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

       •   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;

       •   "length undef" now returns undef.

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

       •   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.

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

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

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

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

Core Enhancements
   Unicode Character Database 5.1.0
       The copy of the Unicode Character Database included in Perl 5.11.0 has been updated to 5.1.0 from
       5.0.0. See <http://www.unicode.org/versions/Unicode5.1.0/#Notable_Changes> for the notable changes.

   A proper interface for pluggable Method Resolution Orders
       As of Perl 5.11.0 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 reimplemented
       implemented as a plugin, without changing its Perl-space interface. See perlmroapi for more
       information.

   The "overloading" pragma
       This pragma allows you to lexically disable or enable overloading for some or all operations. (Yuval
       Kogman)

   "\N" regex escape
       A new regex escape has been added, "\N". It will match any character that is not a newline,
       independently from the presence or absence of the single line match modifier "/s". (If "\N" is
       followed by an opening brace and by a letter, perl will still assume that a Unicode character name is
       coming, so compatibility is preserved.) (Rafael Garcia-Suarez)

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

           use 5.11.0;

       will now imply:

           use strict;
           use feature ':5.11';

   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.

   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. (chromatic)

   DTrace support
       Some support for DTrace has been added. 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" is now more flexible
       The "each" function can now operate on arrays.

   Y2038 compliance
       Perl's core time-related functions are now Y2038 compliant. (With 29 years to spare!)

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

   // in where 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.

Modules and Pragmata
   Dual-lifed modules moved
       Dual-lifed modules maintained primarily in the Perl core now live in dist/.  Dual-lifed modules
       maintained primarily on CPAN now live in cpan/

       In previous releases of Perl, it was customary to enumerate all module changes in this section of the
       "perldelta" file.   From 5.11.0 forward only notable updates (such as new or deprecated modules )
       will be listed in this section. For a complete reference to the versions of modules shipped in a
       given release of perl, please see Module::CoreList.

   New Modules and Pragmata
       "autodie"
           This 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.

       "Compress::Raw::Bzip2"
           This has been added to the core (version 2.020).

       "parent"
           This pragma establishes an ISA relationship with base classes at compile time. It provides the
           key feature of "base" without the feature creep.

       "Parse::CPAN::Meta"
           This has been added to the core (version 1.39).

   Pragmata Changes
       "overloading"
           See "The "overloading" pragma" above.

       "attrs"
           The "attrs" pragma has been removed. It had been marked as deprecated since 5.6.0.

       "charnames"
           The Unicode NameAliases.txt database file has been added. 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}".

       "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.

       "mro"
           Upgraded from version 1.00 to 1.01. Performance for single inheritance is 40% faster - see
           "Performance Enhancements" below.

           "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".

   Updated Modules
       "ExtUtils::MakeMaker"
           Upgraded from version 6.42 to 6.55_02.

           Note that "ExtUtils::MakeMaker::bytes" and "ExtUtils::MakeMaker::vmsish" have been removed from
           this distribution.

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

           Note that one side-effect of the 2.x to 3.x upgrade is that the experimental
           "Test::Harness::Straps" module (and its supporting "Assert", "Iterator", "Point" and "Results"
           modules) have been removed. If you still need this, then they are available in the (unmaintained)
           "Test-Harness-Straps" distribution on CPAN.

       "UNIVERSAL"
           Upgraded from version 1.04 to 1.05.

           "UNIVERSAL->import()" is now deprecated.

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

       h2xs
           No longer incorrectly treats enum values like macros (Daniel Burr).

           Now handles C++ style constants ("//") properly in enums. (A patch from Rainer Weikusat was used;
           Daniel Burr also proposed a similar fix).

       perl5db.pl
           "LVALUE" subroutines now work under the debugger.

           The debugger now correctly handles proxy constant subroutines, and subroutine stubs.

       perlbug
           perlbug now uses %Module::CoreList::bug_tracker to print out upstream bug tracker URLs.

           Where the user names a module that their bug report is about, and we know the URL for its
           upstream bug tracker, 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 upstream.

       perlthanks
           Perl 5.11.0 added a new utility perlthanks, which is a variant of perlbug, but for sending non-bug-reports nonbug-reports
           bug-reports to the authors and maintainers of Perl. Getting nothing but bug reports can become a
           bit demoralising: we'll see if this changes things.

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

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

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

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

Changes to Existing Documentation
       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.

       The file 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.

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

       •   Documented -X overloading.

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

       •   Documented when as a syntax modifier

       •   Eliminated "Old Perl threads tutorial", which describes 5005 threads.

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

       •   Correct previous documentation: v-strings are not deprecated

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

       •   Added security contact information to perlsec

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

       •   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.

       •   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.

       •   Empty "DESTROY" methods are no longer called.

       •   Faster "Perl_sv_utf8_upgrade()"

       •   Speed up "keys" on empty hash

Installation and Configuration Improvements
   ext/ reorganisation
       The layout of directories in ext has been revised. Specifically, all extensions are now flat, and at
       the top level, with "/" in pathnames replaced by "-", so that ext/Data/Dumper/ is now
       ext/Data-Dumper/, etc.  The names of the extensions as specified to Configure, and as reported by
       %Config::Config under the keys "dynamic_ext", "known_extensions", "nonxs_ext" and "static_ext" have
       not changed, and still use "/". Hence this change will not have any affect once perl is installed.
       "Safe" has been split out from being part of "Opcode", and "mro" is now an extension in its own
       right.

       Nearly all dual-life modules have been moved from lib to ext, and will now appear as known
       "nonxs_ext". This will made no difference to the structure of an installed perl, nor will the modules
       installed differ, unless you run Configure with options to specify an exact list of extensions to
       build. In this case, you will rapidly become aware that you need to add to your list, because various
       modules needed to complete the build, such as "ExtUtils::ParseXS", have now become extensions, and
       without them the build will fail well before it attempts to run the regression tests.

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

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

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

       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.

       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".

   Compilation improvements
       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.

   Platform Specific Changes
       AIX Removed libbsd for AIX 5L and 6.1. Only "flock()" was used from libbsd.

           Removed libgdbm for AIX 5L and 6.1. The libgdbm is delivered as an optional package with the AIX
           Toolbox. Unfortunately the 64 bit version is broken.

           Hints changes mean that AIX 4.2 should work again.

       Cygwin
           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.

       DomainOS
           Support for Apollo DomainOS was removed in Perl 5.11.0

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

       Irix
           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.

       Haiku
           Patches from the Haiku maintainers have been merged in. Perl should now build on Haiku.

       MachTen
           Support for Tenon Intersystems MachTen Unix layer for MacOS Classic was removed in Perl 5.11.0

       MiNT
           Support for Atari MiNT was removed in Perl 5.11.0.

       MirOS BSD
           Perl should now build on MirOS BSD.

       NetBSD
           Hints now supports versions 5.*.

       Stratus VOS
           Various changes from Stratus have been merged in.

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

       Win32
           Improved message window handling means that "alarm" and "kill" messages will no longer be dropped
           under race conditions.

       VMS 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.

           VMS now supports "getgrgid".

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

           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.

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

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

       •   "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.

       •   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.

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

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

       •   The debugger now works with lvalue subroutines.

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

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

       •   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].

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

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

       •   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.

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

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

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

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

       •   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

       •   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].

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

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

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

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

       •   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)*$/

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

       •   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

       •   On Windows, '.\foo' and '..\foo'  were treated differently than './foo' and '../foo' by "do" and
           "require" [RT #63492].

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

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

       •   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".

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

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

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

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

       •   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].

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

       •   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].

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

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

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

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

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

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

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

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

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

       •   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].

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

       •   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].

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

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

       •   "-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].

       •   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

       •   Previously missing files from Unicode 5.1 Character Database are now included.

       •   "TMPDIR" is now honored when opening an anonymous temporary file

New or Changed Diagnostics
       "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.

       "Can't locate package %s for the parents of %s"
           This warning has been removed. In general, it only got produced in conjunction with other
           warnings, and removing it allowed an ISA lookup optimisation to be added.

       "v-string in use/require is non-portable"
           This warning has been removed.

       "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.

Changed Internals
       •   TODO: "SVt_RV" is gone. RVs are now stored in IVs

       •   TODO: REGEXPs are first class

       •   TODO: OOK is reworked, such that an OOKed scalar is PV not PVIV

       •   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.

       •   "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.

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

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

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

       •   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.

           "SVf_UTF8"
               This 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.

           "SVs_TEMP"
               Call "Perl_sv_2mortal()" on the new SV.

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

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

       •   The functions "PerlIO_find_layer" and "PerlIO_list_alloc" are now exported.

       •   "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 deference into the
           interpreter structure under ithreads, and a global variable otherwise.

       •   "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.

       •   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.

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

       •   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.

       •   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.

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

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

       •   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.

       •   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).

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

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

       •   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.

New Tests
       Many modules updated from CPAN incorporate new tests.

       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. (Jerry Hedden).

       Some core-specific tests have been added:

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

       t/io/perlio_fail.t
           Check that bad layers fail.

       t/io/perlio_leaks.t
           Check that PerlIO layers are not leaking.

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

       t/io/perlio.t
           General PerlIO tests.

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

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

       t/op/dbm.t
           Tests for "dbmopen" and "dbmclose".

       t/op/index_thr.t
           Tests for the interaction of "index" and threads.

       t/op/pat_thr.t
           Tests for the interaction of esoteric patterns and threads.

       t/op/qr_gc.t
           Test that "qr" doesn't leak.

       t/op/reg_email_thr.t
           Tests for the interaction of regex recursion and threads.

       t/op/regexp_qr_embed_thr.t
           Tests for the interaction of patterns with embedded "qr//" and threads.

       t/op/regexp_unicode_prop.t
           Tests for Unicode properties in regular expressions.

       t/op/regexp_unicode_prop_thr.t
           Tests for the interaction of Unicode properties and threads.

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

       t/op/reg_posixcc.t
           Check that POSIX character classes behave consistently.

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

       t/op/setpgrpstack.t
           Check that "setpgrp" works.

       t/op/substr_thr.t
           Tests for the interaction of "substr" and threads.

       t/op/upgrade.t
           Check that upgrading and assigning scalars works.

       t/uni/lex_utf8.t
           Check that Unicode in the lexer works.

       t/uni/tie.t
           Check that Unicode and "tie" work.

Known Problems
       This is a list of some significant unfixed bugs, which are regressions from either 5.10.0 or 5.8.x.

       •   "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

       •   The "charnames" pragma may generate a run-time error when a regex is interpolated [RT #56444]:

               use charnames ':full';
               my $r1 = qr/\N{THAI CHARACTER SARA I}/;
               "foo" =~ $r1;    # okay
               "foo" =~ /$r1+/; # runtime error

           A workaround is to generate the character outside of the regex:

               my $a = "\N{THAI CHARACTER SARA I}";
               my $r1 = qr/$a/;

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

Deprecations
       The following items are now deprecated.

       •   "Switch" is buggy and should be avoided. From perl 5.11.0 onwards, it is intended that any use of
           the core version of this module will emit a warning, and that the module will eventually be
           removed from the core (probably in perl 5.14.0). See "Switch statements" in perlsyn for its
           replacement.

       •   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.

           •   "Class::ISA"

           •   "Pod::Plainer"

           •   "Shell"

           Currently support to install from CPAN without a force is "TODO" in CPAN and CPANPLUS. This will
           be addressed before 5.12.0 ships.

       •   "suidperl" has been removed. It used to provide a mechanism to emulate setuid permission bits on
           systems that don't support it properly.

       •   Deprecate assignment to $[

       •   Remove attrs, which has been deprecated since 1999/10/02.

       •   Deprecate use of the attribute :locked on subroutines.

       •   Deprecate using "locked" with the attributes pragma.

       •   Deprecate using "unique" with the attributes pragma.

       •   warn if ++ or -- are unable to change the value because it's beyond the limit of representation

           This uses a new warnings category: "imprecision".

       •   Make lc/uc/lcfirst/ucfirst warn when passed undef.

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

       •   Make the new warning report undef constants as undef

       •   Add a new warning, "Prototype after '%s'"

       •   Tweak the "Illegal character in prototype" warning so it's more precise when reporting illegal
           characters after _

       •   Unintended interpolation of $\ in regex

       •   Make overflow warnings in gmtime/localtime only occur when warnings are on

       •   Improve mro merging error messages.

           They are now very similar to those produced by Algorithm::C3.

       •   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.

       •   Explicitely point to $. when it causes an uninitialized warning for ranges in scalar context

       •   Deprecated 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. Using them
           will incur a warning.

Acknowledgements
       Some of the work in this release was funded by a TPF grant funded by Dijkmat BV, The Netherlands.

       Steffen Mueller and David Golden in particular helped getting CPAN modules polished and synchronised
       with their in-core equivalents.

       Craig Berry was tireless in getting maint to run under VMS, no matter how many times we broke it for
       him.

       The other core committers contributed most of the changes, and applied most of the patches sent in by
       the hundreds of contributors listed in AUTHORS.

       Much of the work of categorizing changes in this perldelta file was contributed by the following
       porters using changelogger.bestpractical.com:

       Nicholas Clark, leon, shawn, alexm, rjbs, rafl, Pedro Melo, brunorc, anonymous, X, Tom Hukins,
       anonymous, Jesse, dagolden, Moritz Onken, Mark Fowler, chorny, anonymous, tmtm

       Finally, thanks to Larry Wall, without whom none of this would be necessary.

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

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

       If the bug you are reporting has security implications, which make it inappropriate to send to a
       publicly archived mailing list, then please send it to perl5-security-report@perl.org. This points to
       a closed subscription unarchived mailing list, which includes all the core committers, who 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.



perl v5.12.5                                     2012-11-03                                 PERL5110DELTA(1)