perl5120delta(1)



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

NAME
       perl5120delta - what is new for perl v5.12.0

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

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

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

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

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

       There are several advantages to this:

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

       o   $VERSION is set at compile time

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

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

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

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

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

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

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

           use 5.12.0;

       means:

           use strict;
           use feature ':5.12';

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

       Changes to type-based dispatch

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

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

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

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

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

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

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

       Smart match and overloading

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

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

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

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

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

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

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

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

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

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

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

       o   "length undef" now returns undef.

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

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

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

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

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

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

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

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

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

       The following items are now deprecated:

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

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

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

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

               my $pi = 4;

           because no attribute processing is done for an empty list.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

           Version 2.06_01 has been added to the Perl core.

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

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

           Version 0.001 has been added to the Perl core.

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

           Version 0.223 has been added to the Perl core.

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

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

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

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

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

       "bignum"
           Upgraded from version 0.22 to 0.23.

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

           Upgraded from version 1.06 to 1.07.

       "constant"
           Upgraded from version 1.13 to 1.20.

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

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

           Upgraded from version 1.17 to 1.19.

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

           "feature" now includes the "unicode_strings" feature:

               use feature "unicode_strings";

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

           Upgraded from version 1.11 to 1.16.

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

           Upgraded from version 0.02 to 0.03.

       "lib"
           Upgraded from version 0.5565 to 0.62.

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

           Upgraded from version 1.00 to 1.02.

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

           Upgraded from version 1.06 to 1.10.

       "threads"
           Upgraded from version 1.67 to 1.75.

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

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

           Upgraded from version 0.74 to 0.82.

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

           Upgraded from version 1.06 to 1.09.

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

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

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

       "AutoLoader"
           Upgraded from version 5.63 to 5.70.

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

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

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

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

       "CGI"
           Upgraded from version 3.29 to 3.48.

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

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

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

       "CPAN"
           Upgraded from version 1.9205 to 1.94_56.

       "CPANPLUS"
           Upgraded from version 0.84 to 0.90.

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

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

       "DB_File"
           Upgraded from version 1.816_1 to 1.820.

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

       "Digest"
           Upgraded from version 1.15 to 1.16.

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

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

       "Encode"
           Upgraded from version 2.23 to 2.39.

       "Exporter"
           Upgraded from version 5.62 to 5.64_01.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

       "NEXT"
           Upgraded from version 0.60_01 to 0.64.

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

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

       "PerlIO"
           Upgraded from version 1.04 to 1.06.

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

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

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

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

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

       "Safe"
           Upgraded from version 2.12 to 2.22.

       "SelfLoader"
           Upgraded from version 1.11 to 1.17.

       "Storable"
           Upgraded from version 2.18 to 2.22.

       "Switch"
           Upgraded from version 2.13 to 2.16.

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

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

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

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

       "Test"
           Upgraded from version 1.25 to 1.25_02.

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

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

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

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

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

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

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

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

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

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

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

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

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

       "Win32"
           Upgraded from version 0.34 to 0.39.

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

       "XSLoader"
           Upgraded from version 0.08 to 0.10.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

   Deprecated Modules and Pragmata
       See "Deprecated Modules" above.

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

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

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

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

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

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

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

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

       o   Documented -X overloading.

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

       o   Documented "when" as a syntax modifier.

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

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

       o   Correct previous documentation: v-strings are not deprecated

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

       o   Security contact information is now part of perlsec.

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

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

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

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

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

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

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

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

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

       o   Empty "DESTROY" methods are no longer called.

       o   "Perl_sv_utf8_upgrade()" is now faster.

       o   "keys" on empty hash is now faster.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

           Two flag bits are currently supported.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

               TEST_JOBS=3 make test_harness  # Run 3 tests in parallel

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

           o   "Bad plugin affecting keyword '%s'"

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

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

           o   "Lexing code internal error (%s)"

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

           o   "Overloaded dereference did not return a reference"

           o   "Overloaded qr did not return a REGEXP"

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

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

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

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

               This uses a new warnings category: "imprecision".

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

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

           o   "Prototype after '%s'"

           o   "panic: sv_chop %s"

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

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

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

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

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

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

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

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

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

           The two warnings:

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

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

             no warnings 'illegalproto';

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

       o   "Deep recursion on subroutine "%s""

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

       The following diagnostic messages have been removed:

       o   "Runaway format"

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

       o   The debugger now works with lvalue subroutines.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

               Exiting given via last at foo.pl line 123

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

       MirOS BSD
           Perl should now build on MirOS BSD.

   Discontinued Platforms
       Domain/OS
       MiNT
       Tenon MachTen

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

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

           o   Hints changes mean that AIX 4.2 should work again.

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

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

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

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

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

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

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

       NetBSD
           o   Hints now supports versions 5.*.

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

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

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

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

           o   VMS now supports "getgrgid".

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

       If the bug you are reporting has security implications, which make it
       inappropriate to send to a publicly archived mailing list, then please
       send it to perl5-security-report@perl.org. This points to a closed
       subscription unarchived mailing list, which includes all the core
       committers, who will be able to help assess the impact of issues,
       figure out a resolution, and help co-ordinate the release of patches to
       mitigate or fix the problem across all platforms on which Perl is
       supported. Please only use this address for security issues in the Perl
       core, not for modules independently distributed on CPAN.

SEE ALSO
       The Changes file for an explanation of how to view exhaustive details
       on what changed.

       The INSTALL file for how to build Perl.

       The README file for general stuff.

       The Artistic and Copying files for copyright information.

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

perl v5.26.0                      2017-09-12                  PERL5120DELTA(1)

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