Man1 - perl5120delta.1perl

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:

• $VERSION is parsed in exactly the same way as use NAME VERSION
• $VERSION is set at compile time
• $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.
• Eliminates $VERSION = ... and eval $VERSION clutter
• 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.

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.

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;

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.

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

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.

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 allows 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.

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.

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.)

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.

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.

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

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.

The each, keys, values function can now operate on arrays.

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

The variable $, may now be tied.

// now behaves like || in when clauses

You can now set -W from the PERL5OPT environment variable

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

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.

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.

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.

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.

In @INC, ARCHLIB and PRIVLIB now occur 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.

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.

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).)

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:

• 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.)

• 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.
• The boolkeys op has moved to the group of hash ops. This breaks binary compatibility.
• 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.
• The semantics of use feature :5.10* have changed slightly. See Modules and Pragmata for more information.
• 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.
• 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.
• 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.
• 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.
• 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.

“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.

“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.

“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.

“:Fetch”

Upgraded from version 0.14 to 0.24.

“:Path”

Upgraded from version 2.04 to 2.08_01.

“: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.

“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.

See Deprecated Modules above.

• perlhaiku contains instructions on how to build perl for the Haiku platform.
• perlmroapi describes the new interface for pluggable Method Resolution Orders.
• 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.
• perlrepository describes how to access the perl source using the git version control system.
• perlpolicy extends the Social contract about contributed modules into the beginnings of a document on Perl porting policies.

• 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.
• 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.
• 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.
• 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 described 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 notice.
• Security contact information is now part of perlsec.
• 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.
• 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.
• 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.
• The documentation for $1 in perlvar.pod has been clarified.
• \N{U+=/=code point=/}= is now documented.

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.

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.

• Significant cleanups to core tests to ensure that language and interpreter features are not used before they’re tested.
• make test_porting now runs a number of important pre-commit checks which might be of use to anyone working on the Perl core.
• 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.
• t/porting/manifest.t now tests that all files listed in MANIFEST are present.
• t/op/while_readdir.t tests that a bare readdir in while loop sets $_.
• t/comp/retainedlines.t checks that the debugger can retain source lines from eval.
• t/io/perlio_fail.t checks that bad layers fail.
• t/io/perlio_leaks.t checks that PerlIO layers are not leaking.
• t/io/perlio_open.t checks that certain special forms of open work.
• t/io/perlio.t includes general PerlIO tests.
• t/io/pvbm.t checks that there is no unexpected interaction between the internal types PVBM and PVGV.
• t/mro/package_aliases.t checks that mro works properly in the presence of aliased packages.
• t/op/dbm.t tests dbmopen and dbmclose.
• t/op/index_thr.t tests the interaction of index and threads.
• t/op/pat_thr.t tests the interaction of esoteric patterns and threads.
• t/op/qr_gc.t tests that qr doesn’t leak.
• t/op/reg_email_thr.t tests the interaction of regex recursion and threads.
• t/op/regexp_qr_embed_thr.t tests the interaction of patterns with embedded qr// and threads.
• t/op/regexp_unicode_prop.t tests Unicode properties in regular expressions.
• t/op/regexp_unicode_prop_thr.t tests the interaction of Unicode properties and threads.
• t/op/reg_nc_tie.t tests the tied methods of Tie::Hash::NamedCapture.
• t/op/reg_posixcc.t checks that POSIX character classes behave consistently.
• t/op/re.t checks that exportable re functions in universal.c work.
• t/op/setpgrpstack.t checks that setpgrp works.
• t/op/substr_thr.t tests the interaction of substr and threads.
• t/op/upgrade.t checks that upgrading and assigning scalars works.
• t/uni/lex_utf8.t checks that Unicode in the lexer works.
• t/uni/tie.t checks that Unicode and tie work.
• t/comp/final_line_num.t tests whether line numbers are correct at EOF
• t/comp/form_scope.t tests format scoping.
• t/comp/line_debug.t tests whether @{"_<$file"} works.
• t/op/filetest_t.t tests if -t file test works.
• t/op/qr.t tests qr.
• t/op/utf8cache.t tests malfunctions of the utf8 cache.
• t/re/uniprops.t test unicodes \p{} regex constructs.
• 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.
• 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.

• 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.
• Perl 5.12 provides a number of new diagnostic messages to help you write better code. See perldiag for details of these new messages.
  • Bad plugin affecting keyword %s
  • gmtime(%.0f) too large
  • Lexing code attempted to stuff non-Latin-1 character into Latin-1 input
  • Lexing code internal error (%s)
  • localtime(%.0f) too large
  • Overloaded dereference did not return a reference
  • Overloaded qr did not return a REGEXP
  • Perl_pmflag() is deprecated, and will be removed from the XS API
  • 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.
  • 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.
  • lc, uc, lcfirst, and ucfirst warn when passed undef.
  • Show constant in "Useless use of a constant in void context"
  • Prototype after %s
  • 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.
  • The fatal error Malformed UTF-8 returned by \N is now produced if the charnames handler returns malformed UTF-8.
  • 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.
  • Invalid hexadecimal number in \N{U+...} is a new fatal error triggered when the character constant represented by ... is not a valid hexadecimal number.
  • 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{...}.
  • 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.
  • 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.

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

• 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.

• 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.
• Illegal character in prototype warning is now more precise when reporting illegal characters after _
• mro merging error messages 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.
• Perl now explicitly points to $. when it causes an uninitialized warning for ranges in scalar context.
• split now warns when called in void context.
• printf-style functions called with too few arguments will now issue the warning "Missing argument in %s" [perl #71000]
• Perl now properly returns a syntax error instead of segfaulting if each, keys, or values is used without an argument.
• 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.
• overload no longer implicitly unsets fallback on repeated ’use overload’ lines.
• POSIX::strftime() can now handle Unicode characters in the format string.
• The syntax category was removed from 5 warnings that should only be in deprecated.
• Three fatal pack=/=unpack error messages have been normalized to panic: %s
• 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.
• 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.
• 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\{.
• 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:

• Runaway format
• Cant 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.
• v-string in use/require is non-portable

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.

Domain/OS

MiNT

Tenon MachTen

AIX

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

• 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.
• Hints changes mean that AIX 4.2 should work again.

Cygwin

Perl now supports IPv6 on Cygwin 1.7 and newer.

• 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)

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

• 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

Fix thread library selection [perl #69686]

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.

NetBSD

Hints now supports versions 5.*.

OpenVMS

-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.

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

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.

Windows

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.

• Initial support for building Perl with MinGW-w64 is now available.
• 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.
• 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.
• 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.
• 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.
• flock() will now set sensible error codes in $!. Previous Perl versions copied the value of $^E into $!, which caused much confusion.
• select() now supports all empty =fd_set=s more correctly.
• .\foo and ..\foo were treated differently than ./foo and ../foo by do and require [RT #63492].
• Improved message window handling means that alarm and kill messages will no longer be dropped under race conditions.
• 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.