perl5120delta - what is new for perl v5.12.0


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

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

   You can see the list of those changes in the 5.10.1 release notes

Core Enhancements

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

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

   There are several advantages to this:

   *   $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.

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

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

       use 5.12.0;


       use strict;
       use feature ':5.12';

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

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

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

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

   Pluggable keywords
   Extension modules can now cleanly hook into the Perl parser to define
   new kinds of keyword-headed expression and compound statement. The
   syntax following the keyword is defined entirely by the extension. This
   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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Potentially Incompatible Changes

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

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

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

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

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

   @INC reorganization
   In @INC, "ARCHLIB" and "PRIVLIB" now occur after 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

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

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

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

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

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

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

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

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

   Changes to type-based dispatch

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

   *   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

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

   Other potentially incompatible changes
   *   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.


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

   The following items are now deprecated:

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

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

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

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

           my $pi = 4;

       because no attribute processing is done for an empty list.

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

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

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

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

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

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

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

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

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

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

   Numerous Perl 4-era libraries,,,,,,,,,,,,,,,,,,,,,,,,,,,, and are all now deprecated.
       Earlier, Perl's developers intended to remove these libraries from
       Perl's core for the 5.14.0 release.

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

Unicode overhaul

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

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

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

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

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

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

   *   "\X" will not break apart a "CRLF" sequence.

   *   "\X" will now match a sequence which includes the "ZWJ" and "ZWNJ"

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

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

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

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

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

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

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

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

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

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

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

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

   The Numeric type property has been extended to include the Unihan

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

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

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

   Earlier versions of Perl erroneously exposed certain properties that
   are supposed to be Unicode internal-only.  Use of these in regular
   expressions will now generate, if enabled, a deprecation warning
   message.  The properties are: Other_Alphabetic,
   Other_Default_Ignorable_Code_Point, Other_Grapheme_Extend,
   Other_ID_Continue, Other_ID_Start, Other_Lowercase, Other_Math, and

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

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

Modules and Pragmata

   New Modules and Pragmata
       "autodie" 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.

       Version 2.024 has been added to the Perl core.

       "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" 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.

       Version 1.40 has been added to the Perl core.

       Version 1.03 has been added to the Perl core.

       Version 2.4 has been added to the Perl core.

       Version 0.003 has been added to the Perl core.

   Updated Pragmata
       Upgraded from version 2.13 to 2.15.

       Upgraded from version 0.22 to 0.23.

       "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

       Upgraded from version 1.06 to 1.07.

       Upgraded from version 1.13 to 1.20.

       "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.

       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" 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.

       Upgraded from version 0.5565 to 0.62.

       "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" now allow overloading of 'qr'.

       Upgraded from version 1.06 to 1.10.

       Upgraded from version 1.67 to 1.75.

       Upgraded from version 1.14 to 1.32.

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

       Upgraded from version 1.06 to 1.09.

   Updated Modules
       Upgraded from version 0.24 to 0.38.

       Upgraded from version 1.38 to 1.54.

       Upgraded from version 0.79 to 0.87.

       Upgraded from version 5.63 to 5.70.

       Upgraded from version 0.74 to 0.78.

       Upgraded from version 1.05 to 1.12.

       Upgraded from version 0.83 to 0.96.

       Upgraded from version 1.09 to 1.11_01.

       Upgraded from version 3.29 to 3.48.

       Upgraded from version 0.33 to 0.36.

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

       Upgraded from version 2.008 to 2.024.

       Upgraded from version 1.9205 to 1.94_56.

       Upgraded from version 0.84 to 0.90.

       Upgraded from version 0.06_02 to 0.46.

       Upgraded from version 2.121_14 to 2.125.

       Upgraded from version 1.816_1 to 1.820.

       Upgraded from version 3.13 to 3.19.

       Upgraded from version 1.15 to 1.16.

       Upgraded from version 2.36_01 to 2.39.

       Upgraded from version 5.45 to 5.47.

       Upgraded from version 2.23 to 2.39.

       Upgraded from version 5.62 to 5.64_01.

       Upgraded from version 0.21 to 0.27.

       Upgraded from version 1.13 to 1.16.

       Upgraded from version 0.2 to 0.22.

       Upgraded from version 1.44 to 1.55.

       Upgraded from version 6.42 to 6.56.

       Upgraded from version 1.51_01 to 1.57.

       Upgraded from version 2.18_02 to 2.21.

       Upgraded from version 0.14 to 0.24.

       Upgraded from version 2.04 to 2.08_01.

       Upgraded from version 0.18 to 0.22.

       Upgraded from version 0.82 to 0.84.

       Upgraded from version 1.07 to 1.08.

       Upgraded from version 2.37 to 2.38.

       Upgraded from version 1.23_01 to 1.25_02.

       Upgraded from version 1.07 to 1.10.

       Upgraded from version 0.40_1 to 0.54.

       Upgraded from version 1.05 to 2.01.

       Upgraded from version 1.12 to 1.14.

       Upgraded from version 0.18 to 0.21.

       Upgraded from version 0.01 to 0.02.

       Upgraded from version 0.04 to 0.06.

       Upgraded from version 1.88 to 1.89_01.

       Upgraded from version 0.16 to 0.19.

       Upgraded from version 0.21 to 0.24.

       Upgraded from version 1.37 to 1.56.

       Upgraded from version 1.01_02 to 1.01_03.

       Upgraded from version 3.07_01 to 3.08.

       Upgraded from version 0.2808_01 to 0.3603.

       Upgraded from version 2.12 to 2.29.

       Upgraded from version 0.12 to 0.16.

       Upgraded from version 0.22 to 0.34.

       Upgraded from version 0.01 to 0.06.

       Upgraded from version 3.6 to 3.9.

       Upgraded from version 2.33 to 2.36.

       Upgraded from version 0.60_01 to 0.64.

       Upgraded from version 0.32 to 0.36.

       Upgraded from version 0.01 to 0.02.

       Upgraded from version 1.04 to 1.06.

       Upgraded from version 1.35 to 1.37.

       Upgraded from version 3.14_02 to 3.15_02.

       Upgraded from version 0.01 to 1.02.

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

       Upgraded from version 3.05 to 3.13.

       Upgraded from version 2.12 to 2.22.

       Upgraded from version 1.11 to 1.17.

       Upgraded from version 2.18 to 2.22.

       Upgraded from version 2.13 to 2.16.

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

       Upgraded from version 0.22 to 0.27.

       Upgraded from version 1.12 to 2.02.

       Upgraded from version 0.18 to 0.20.

       Upgraded from version 1.25 to 1.25_02.

       Upgraded from version 2.64 to 3.17.

       Upgraded from version 0.72 to 0.94.

       Upgraded from version 2.0.0 to 2.02.

       Upgraded from version 3.26 to 3.27.

       Upgraded from version 3.03 to 3.03_01.

       Upgraded from version 2.00 to 2.11.

       Upgraded from version 2.01 to 2.09.

       Upgraded from version 1.37 to 1.38.

       Upgraded from version 1.9711 to 1.9719.

       Upgraded from version 1.18 to 1.1901_01.

       Upgraded from version 1.12 to 1.15.

       Upgraded from version 0.52 to 0.52_01.

       Upgraded from version 1.02 to 1.03.

       Upgraded from version 0.34 to 0.39.

       Upgraded from version 0.1001_01 to 0.1101.

       Upgraded from version 0.08 to 0.10.

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

       Removed from the Perl core.  Prior version was 'undef'.

       Removed from the Perl core.  Prior version was 5.50.

       Removed from the Perl core.  Prior version was 'undef'.

       Removed from the Perl core.  Prior version was 1.03.

       Removed from the Perl core.  Prior version was 6.42.

       Removed from the Perl core.  Prior version was 6.42.

       Removed from the Perl core.  Prior version was 2.3.

       Removed from the Perl core.  Prior version was 0.02.

       Removed from the Perl core.  Prior version was 0.02.

       Removed from the Perl core.  Prior version was 0.01.

       Removed from the Perl core.  Prior version was 0.01.

       Removed from the Perl core.  Prior version was 0.26_01.

       Removed from the Perl core.  Prior version was 0.01.

       Removed from the Perl core.  Prior version was 1.1.

   Deprecated Modules and Pragmata
   See "Deprecated Modules" above.


   New Documentation
   *   perlhaiku contains instructions on how to build perl for the Haiku

   *   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.

   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.

   *   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

   *   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

   *   Documented "when" as a syntax modifier.

   *   Eliminated "Old Perl threads tutorial", which described 5005

       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.

   * 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.

Selected 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.

   *   "Perl_sv_utf8_upgrade()" is now faster.

   *   "keys" on empty hash is now faster.

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

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

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

Installation and Configuration Improvements

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

   *   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

   *   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".

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

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

   *   "perl -V" now reports use of the compile-time options

   *   As part of the flattening of ext, all extensions on all platforms
       are built by This replaces the Unix-specific
       ext/util/make_ext, VMS-specific and Win32-specific

Internal Changes

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

   *   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

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

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

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

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

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

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

   *   "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

   *   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

       Two flag bits are currently supported.

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

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

       There is also a wrapper that takes constant strings,

   *   The function "Perl_croak_xs_usage" has been added as a wrapper to

   *   Perl now exports the functions "PerlIO_find_layer" and

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

   *   "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

   *   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

   *   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/ 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


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

           TEST_JOBS=3 make test_harness  # Run 3 tests in parallel

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

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

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

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

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

   *   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

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

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

   *   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

   *   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

   *   t/op/reg_posixcc.t checks that POSIX character classes behave

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

   *   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

   *   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.

New or Changed Diagnostics

   New Diagnostics
   *   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

       *   "lvalue attribute ignored after the subroutine has been

           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

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

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

   *   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

   *   "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

   *   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

       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"

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

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

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

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.  It also
       now handles C++ style comments ("//") properly in enums.

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

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

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

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

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

Selected Bug Fixes

   *   U+0FFFF is now a legal character in regular expressions.

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

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

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

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

   *   Fixes for lexer API changes in 5.11.2 which broke NYTProf's savesrc

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

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

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

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

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

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

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

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

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

   *   Smart match against @_ sometimes gave false negatives. [perl

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

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

   *   Tie::Hash::NamedCapture::* will not abort if passed bad input (RT

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

   *   "-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. (This fix
       is also present in 5.10.1)

   *   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

   *   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

   *   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

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

   *   "shmget" was limited to a 32 bit segment size on a 64 bit OS [RT

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

           Exiting given via last at line 123

   *   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

   *   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

   *   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

   *   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

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

   *   Use of a UTF-8 "tr//" within a closure could cause a segfault [RT

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

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

   *   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

   *   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

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

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

Platform Specific Changes

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

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

   MirOS BSD
       Perl should now build on MirOS BSD.

   Discontinued Platforms
   Tenon MachTen

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

       *   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.

       *   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 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,

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

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

       *   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.

       *   Hints now supports versions 5.*.

       *   "-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
 ; 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.

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

       *   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

       *   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

       *   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

           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

       *   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.

Known Problems

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

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

   *   "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

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

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

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


   *   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

       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;


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

   Perl continues to flourish into its third decade thanks to a vibrant
   community of users and developers.  The following people are known to
   have contributed the improvements that became Perl 5.12.0:

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

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

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

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

Reporting Bugs

   If you find what you think is a bug, you might check the articles
   recently posted to the comp.lang.perl.misc newsgroup and the perl bug
   database at <>. There may also be
   information at <>, 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 to be analyzed by
   the Perl porting team.

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


   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.

   <> for a list of issues found
   after this release, as well as a list of CPAN modules known to be
   incompatible with this release.


Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.

Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.

Free Software

Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.

Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.

Free Books

The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.

Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.


Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.

Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.