perldelta for e9827b374

[perl5.git] / pod / perldelta.pod

=encoding utf8

=for comment
To do:
3f40aba3 Merge branch 'ebcdic' into blead
df8c7dee Fix segfault in filehandle duplication
b66f3475 Fix PerlIO_get_cnt and friends

=head1 NAME

[ this is a template for a new perldelta file.  Any text flagged as XXX needs
to be processed before release. ]

perldelta - what is new for perl v5.19.4

=head1 DESCRIPTION

This document describes differences between the 5.19.3 release and the 5.19.4
release.

If you are upgrading from an earlier release such as 5.19.2, first read
L<perl5193delta>, which describes differences between 5.19.2 and 5.19.3.

=head1 Notice

XXX Any important notices here

=head1 Core Enhancements

XXX New core language features go here.  Summarize user-visible core language
enhancements.  Particularly prominent performance optimisations could go
here, but most should go in the L</Performance Enhancements> section.

[ List each enhancement as a =head2 entry ]

=head2 C<rand> now uses a consistent random number generator

Previously perl would use a platform specific random number generator, varying
between the libc rand(), random() or drand48().

This meant that the quality of perl's random numbers would vary from platform
to platform, from the 15 bits of rand() on Windows to 48-bits on POSIX
platforms such as Linux with drand48().

Perl now uses its own internal drand48() implementation on all platforms.
[perl #115928]

=head2 Better 64-bit support

On 64-bit platforms, the internal array functions now use 64-bit offsets,
allowing Perl arrays to hold more than 2**31 elements, if you have the memory
available.

The regular expression engine now supports strings longer than 2**31
characters.  [perl #112790, #116907]

=head2 New slice syntax

The new C<%hash{...}> and C<@array[...]> syntax returns a list of key/value (or
index/value) pairs.

=head1 Security

XXX Any security-related notices go here.  In particular, any security
vulnerabilities closed should be noted here rather than in the
L</Selected Bug Fixes> section.

[ List each security issue as a =head2 entry ]

=head1 Incompatible Changes

=head2 Locale decimal point character no longer leaks outside of
S<C<use locale>> scope (with the exception of $!)

This is actually a bug fix, but some code has come to rely on the bug being
present, so this change is listed here.  The current locale that the program is
running under is not supposed to be visible to Perl code except within the
scope of a S<C<use locale>>.  However, until now under certain circumstances,
the character used for a decimal point (often a comma) leaked outside the
scope.

This continues the work released in Perl 5.19.1.  It turns out that that did
not catch all the leaks, including C<printf> and C<sprintf> not respecting
S<C<use locale>>.  If your code is affected by this change, simply add a
S<C<use locale>>.

Now, the only known place where S<C<use locale>> is not respected is in the
stringification of L<$!|perlvar/$!>.

=head1 Deprecations

XXX Any deprecated features, syntax, modules etc. should be listed here.

=head2 Module removals

XXX Remove this section if inapplicable.

The following modules will be removed from the core distribution in a
future release, and will at that time need to be installed from CPAN.
Distributions on CPAN which require these modules will need to list them as
prerequisites.

The core versions of these modules will now issue C<"deprecated">-category
warnings to alert you to this fact.  To silence these deprecation warnings,
install the modules in question from CPAN.

Note that these are (with rare exceptions) fine modules that you are encouraged
to continue to use.  Their disinclusion from core primarily hinges on their
necessity to bootstrapping a fully functional, CPAN-capable Perl installation,
not usually on concerns over their design.

=over

XXX Note that deprecated modules should be listed here even if they are listed
as an updated module in the L</Modules and Pragmata> section.

=back

[ List each other deprecation as a =head2 entry ]

=head1 Performance Enhancements

=over 4

=item *

The trie performance enhancement for regular expressions has now been extended
to those compiled under C</iaa>.

=back

=head1 Modules and Pragmata

XXX All changes to installed files in F<cpan/>, F<dist/>, F<ext/> and F<lib/>
go here.  If Module::CoreList is updated, generate an initial draft of the
following sections using F<Porting/corelist-perldelta.pl>, which prints stub
entries to STDOUT.  Results can be pasted in place of the '=head2' entries
below.  A paragraph summary for important changes should then be added by hand.
In an ideal world, dual-life modules would have a F<Changes> file that could be
cribbed.

[ Within each section, list entries as a =item entry ]

=head2 New Modules and Pragmata

=over 4

=item *

XXX

=back

=head2 Updated Modules and Pragmata

=over 4

=item *

L<autodie> has been upgraded from version 2.20 to 2.21.

Numerous improvements have been made, many speed-related.  See the F<Changes>
file in the CPAN distribution for full details.

=item *

L<B> has been upgraded from version 1.45 to 1.46.

The fix for [perl #118525] introduced a regression in the behaviour of
C<B::CV::GV>, changing the return value from a C<B::SPECIAL> object on a
C<NULL> C<CvGV> to C<undef>.  C<B::CV::GV> again returns a C<B::SPECIAL> object
in this case.  [perl #119351]

=item *

L<B::Concise> has been upgraded from version 0.98 to 0.99.

The handling of the C<glob> operator, broken since Perl 5.17.6, has been fixed
and handling of the new kvaslice and kvhslice operators have been added.

=item *

L<B::Deparse> has been upgraded from version 1.22 to 1.23.

The new kvaslice and kvhslice operators have been added.

=item *

L<Carp> has been upgraded from version 1.31 to 1.32.

=over 4

=item *

In stack traces, subroutine arguments that are strings are now quoted in a
consistent manner, regardless of what characters they contain and how they're
internally represented.

=item *

C<Carp> now takes care not to clobber the status variables $! and $^E.

=item *

C<Carp> now won't vivify the C<overload::StrVal> glob or subroutine or the
C<overload> stash.

=item *

C<Carp> now avoids some unwanted Unicode warnings on older Perls.  This doesn't
affect behaviour with current Perls.

=item *

C<Carp::Heavy> detects version mismatch with C<Carp>, to give a good error
message if a current (stub) C<Carp::Heavy> gets loaded by an old C<Carp> that
expects C<Carp::Heavy> to provide subroutines.

=back

=item *

L<charnames> has been upgraded from version 1.38 to 1.39.

This module now works on EBCDIC platforms.

=item *

L<CPAN::Meta> has been upgraded from version 2.132140 to 2.132510.

No changes have been made to the installed code other than the version bump to
keep in sync with the latest CPAN release.

=item *

L<CPAN::Meta::Requirements> has been upgraded from version 2.122 to 2.123.

No changes have been made to the installed code other than the version bump to
keep in sync with the latest CPAN release.

=item *

L<Data::Dumper> has been upgraded from version 2.148 to 2.149.

This upgrade is part of a larger change to make the array interface 64-bit safe
by using SSize_t instead of I32 for array indices.

In addition, an EBCDIC fix has been applied.

=item *

L<Devel::Peek> has been upgraded from version 1.13 to 1.14.

This upgrade is part of a larger change to preserve referential identity when
passing C<undef> to a subroutine by using NULL rather than &PL_sv_undef for
nonexistent array elements.

In addition, C<Dump> with no args was broken in Perl 5.19.3, but has now been
fixed.

=item *

L<DynaLoader> has been upgraded from version 1.19 to 1.20.

The documentation now makes it clear, as has always been the case, that
C<dl_unload_file> is only called automatically to unload all loaded shared
objects if the perl interpreter was built with the C macro
DL_UNLOAD_ALL_AT_EXIT defined.  Support for GNU DLD has also been removed.

=item *

L<Encode> has been upgraded from version 2.52 to 2.55.

An erroneous early return in C<decode_utf8> has been removed, and a bug in
C<_utf8_on> under COW has been fixed.  Encode also now uses L<parent> rather
than L<base> throughout.

=item *

L<Exporter> has been upgraded from version 5.69 to 5.70.

A number of typos have been corrected in the documentation.

=item *

L<ExtUtils::CBuilder> has been upgraded from version 0.280205 to 0.280212.

No changes have been made to the installed code other than the version bump to
keep in sync with the latest CPAN release.

=item *

L<ExtUtils::Command> has been upgraded from version 1.17 to 1.18.

No changes have been made to the installed code other than the version bump to
keep in sync with the latest CPAN release.

=item *

L<ExtUtils::MakeMaker> has been upgraded from version 6.72 to 6.76.

Numerous updates and bug fixes are incorporated.  See the F<Changes> file for
full details.

=item *

L<ExtUtils::ParseXS> has been upgraded from version 3.21 to 3.23.

Unquoted "here-doc" markers for typemaps can now be optionally followed by a
semicolon, just like quoted markers.  [perl #119761]

=item *

L<File::Find> has been upgraded from version 1.24 to 1.25.

Better diagnostics are now provided in the case of a failed C<chdir>.

=item *

L<File::Glob> has been upgraded from version 1.20 to 1.21.

C<glob> now warns in the context of C<use warnings "syscalls";> if the supplied
pattern has an internal NUL (C<"\0">) character.

=item *

L<FileCache> has been upgraded from version 1.08 to 1.09.

This upgrade is part of a larger change to use L<parent> rather than L<base>.

=item *

L<Hash::Util::FieldHash> has been upgraded from version 1.12 to 1.13.

This upgrade is part of a larger change to use L<parent> rather than L<base>.

=item *

L<HTTP::Tiny> has been upgraded from version 0.034 to 0.035.

Encoded data from C<post_form> now preserves term order if data is provided as
an array reference.  (They are still sorted for consistency if provided as a
hash reference.)

=item *

L<I18N::LangTags> has been upgraded from version 0.39 to 0.40.

Bosnian has now joined Croatian and Serbian in the lists of mutually
intelligible Slavic languages.  [perl #72594]

=item *

L<IO> has been upgraded from version 1.28 to 1.29.

A minor internals-only change has been made to the XS code.

=item *

L<IPC::Open3> has been upgraded from version 1.15 to 1.16.

This upgrade is part of a larger change to preserve referential identity when
passing C<undef> to a subroutine by using NULL rather than &PL_sv_undef for
nonexistent array elements.

=item *

L<Locale::Codes> has been upgraded from version 3.26 to 3.27.

New codes have been added and the (deprecated) set of FIPS-10 country codes has
been removed.

=item *

L<Math::BigInt> has been upgraded from version 1.9992 to 1.9993.

Cleaned up the L<Math::BigInt> and L<Math::BigFloat> documentation to be more
consistent with other Perl documentation.  [perl #86686]

Added a C<bint> method for rounding towards zero.  [perl #85296]

=item *

L<Math::BigInt::FastCalc> has been upgraded from version 0.30 to 0.31.

This upgrade is part of a larger change to make the array interface 64-bit safe
by using SSize_t instead of I32 for array indices.

=item *

L<Module::CoreList> has been upgraded from version 2.97 to 2.98.

The list of Perl versions covered has been updated.

=item *

L<Module::Load::Conditional> has been upgraded from version 0.54 to 0.58.

C<requires> has been made more robust.  [cpan #83728]

=item *

L<Module::Metadata> has been upgraded from version 1.000014 to 1.000018.

The module's DESCRIPTION has been re-worded regarding safety/security to
satisfy CVE-2013-1437.  Also, versions are now detainted if needed.  [cpan
#88576]

=item *

L<mro> has been upgraded from version 1.13 to 1.14.

This upgrade is part of a larger change to make the array interface 64-bit safe
by using SSize_t instead of I32 for array indices.

=item *

L<Opcode> has been upgraded from version 1.25 to 1.26.

The new kvaslice and kvhslice operators have been added.

=item *

L<parent> has been upgraded from version 0.226 to 0.227.

No changes have been made to the installed code other than the version bump to
keep in sync with the latest CPAN release.

=item *

L<Parse::CPAN::Meta> has been upgraded from version 1.4405 to 1.4407.

No changes have been made to the installed code other than the version bump to
keep in sync with the latest CPAN release.

=item *

L<Perl::OSType> has been upgraded from version 1.003 to 1.005.

The Unix OSType 'bitrig' has been added.

=item *

L<perlfaq> has been upgraded from version 5.0150043 to 5.0150044.

The use of C<gensym> in a number of examples has been removed, the use of C<&>
in subroutine calls is now clarified and several new questions have been
answered.

=item *

L<Pod::Html> has been upgraded from version 1.20 to 1.21.

This upgrade is part of a larger change to use L<parent> rather than L<base>.

=item *

L<re> has been upgraded from version 0.25 to 0.26.

This upgrade is part of a larger change to support 64-bit string lengths in the
regular expression engine.

=item *

L<Scalar::Util> has been upgraded from version 1.31 to 1.32.

The documentation of C<blessed> has been improved to mention the fact that
package "0" is defined but false.

=item *

L<Socket> has been upgraded from version 2.011 to 2.012.

Syntax errors when building on the WinCE platform have been fixed.  [cpan
#87389]

=item *

L<Storable> has been upgraded from version 2.46 to 2.47.

This upgrade is part of a larger change to preserve referential identity when
passing C<undef> to a subroutine by using NULL rather than &PL_sv_undef for
nonexistent array elements.

=item *

L<Term::ReadLine> has been upgraded from version 1.10 to 1.14.

Term::ReadLine::EditLine support has been added.

=item *

L<Time::Piece> has been upgraded from version 1.22 to 1.23.

Day of year parsing (like "%y%j") has been fixed.

=item *

L<Unicode::Collate> has been upgraded from version 0.98 to 0.99.

By default, out-of-range values are replaced with C<U+FFFD> (REPLACEMENT
CHARACTER) when C<UCA_Version> E<gt>= 22, or ignored when C<UCA_Version> E<lt>=
20.  When C<UCA_Version> E<gt>= 22, the weights of out-of-range values can be
overridden.

=item *

L<Unicode::UCD> has been upgraded from version 0.53 to 0.54.

This module now works on EBCDIC platforms.

=item *

L<version> has been upgraded from version 0.9903 to 0.9904.

No changes have been made to the installed code other than the version bump to
keep in sync with the latest CPAN release.

=item *

L<warnings> has been upgraded from version 1.18 to 1.19.

The C<syscalls> warnings category has been added to check for embedded NUL
(C<"\0">) characters in pathnames and string arguments to other system calls.

=item *

L<XS::Typemap> has been upgraded from version 0.10 to 0.11.

XXX TODO

=back

=head2 Removed Modules and Pragmata

=over 4

=item *

XXX

=back

=head1 Documentation

XXX Changes to files in F<pod/> go here.  Consider grouping entries by
file and be sure to link to the appropriate page, e.g. L<perlfunc>.

=head2 New Documentation

XXX Changes which create B<new> files in F<pod/> go here.

=head3 L<XXX>

XXX Description of the purpose of the new file here

=head2 Changes to Existing Documentation

XXX Changes which significantly change existing files in F<pod/> go here.
However, any changes to F<pod/perldiag.pod> should go in the L</Diagnostics>
section.

=head3 L<XXX>

=over 4

=item *

XXX Description of the change here

=back

=head1 Diagnostics

The following additions or changes have been made to diagnostic output,
including warnings and fatal error messages.  For the complete list of
diagnostic messages, see L<perldiag>.

XXX New or changed warnings emitted by the core's C<C> code go here.  Also
include any changes in L<perldiag> that reconcile it to the C<C> code.

=head2 New Diagnostics

XXX Newly added diagnostic messages go under here, separated into New Errors
and New Warnings

=head3 New Errors

=over 4

=item *

XXX L<message|perldiag/"message">

=back

=head3 New Warnings

=over 4

=item *

L<Invalid \0 character in %s for %s: %s\0%s|perldiag/"Invalid \0 character in %s for %s: %s\0%s">

(W syscalls) Embedded \0 characters in pathnames or other system call arguments
produce a warning as of 5.20.  The parts after the \0 were formerly ignored by
system calls.

=back

=head2 Changes to Existing Diagnostics

XXX Changes (i.e. rewording) of diagnostic messages go here

=over 4

=item *

Warnings and errors from the regexp engine are now UTF-8 clean

=item *

The "Unknown switch condition" error message has some slight changes.  This
error triggers when there is an unknown condition in a C<(?(foo))> conditional.
The error message used to read:

    Unknown switch condition (?(%s in regex;

But what %s could be was mostly up to luck.  For C<(?(foobar))>, you might have
seen "fo" or "f".  For Unicode characters, you would generally get a corrupted
string.  The message has been changed to read:

    Unknown switch condition (?(...)) in regex;

Additionally, the C<'E<lt>-- HERE'> marker in the error will now point to the
correct spot in the regex.

=back

=head1 Utility Changes

XXX Changes to installed programs such as F<perlbug> and F<xsubpp> go here.
Most of these are built within the directories F<utils> and F<x2p>.

[ List utility changes as a =head3 entry for each utility and =item
entries for each change
Use L<XXX> with program names to get proper documentation linking. ]

=head3 L<find2perl>

=over 4

=item *

L<find2perl> now handles C<?> wildcards correctly.  [perl #113054]

=back

=head1 Configuration and Compilation

XXX Changes to F<Configure>, F<installperl>, F<installman>, and analogous tools
go here.  Any other changes to the Perl build process should be listed here.
However, any platform-specific changes should be listed in the
L</Platform Support> section, instead.

[ List changes as a =item entry ].

=over 4

=item *

The F<Makefile.PL> for C<SDBM_File> now generates a better F<Makefile>, which
avoids a race condition during parallel makes, which could cause the build to
fail.  This is the last known parallel make problem (on *nix platforms), and
therefore we believe that a parallel make should now always be error free.

=for comment

Strictly only for a build where build files such as F<Makefile.SH> have not
been updated by C<git> in an already configured and built tree.

=back

=head1 Testing

XXX Any significant changes to the testing of a freshly built perl should be
listed here.  Changes which create B<new> files in F<t/> go here as do any
large changes to the testing harness (e.g. when parallel testing was added).
Changes to existing files in F<t/> aren't worth summarizing, although the bugs
that they represent may be covered elsewhere.

[ List each test improvement as a =item entry ]

=over 4

=item *

The test script F<t/bigmem/regexp.t> has been added to test that regular
expression matches on very large strings now succeed as expected.

=item *

Various cases of C<die>, C<last>, C<goto> and C<exit> triggering C<DESTROY> are
now tested by the new test script F<t/op/rt119311.t>.

=item *

The new test script F<t/win32/signal.t> tests that $! and $^E are now preserved
across signal handlers by the Win32 signal emulation code.

=item *

The test script F<t/x2p/find2perl.t> has been added to test the F<find2perl>
program on platforms where it is practical to do so.

=back

=head1 Platform Support

XXX Any changes to platform support should be listed in the sections below.

[ Within the sections, list each platform as a =item entry with specific
changes as paragraphs below it. ]

=head2 New Platforms

XXX List any platforms that this version of perl compiles on, that previous
versions did not.  These will either be enabled by new files in the F<hints/>
directories, or new subdirectories and F<README> files at the top level of the
source tree.

=over 4

=item Bitrig

Compile support has been added for Bitrig, a fork of OpenBSD.

=back

=head2 Discontinued Platforms

Configure hints and conditional code for several very old platforms has been
removed.  We have not received reports for these in many years, typically not
since Perl 5.6.0.

=over 4

=item AT&T 3b1

Configure support for the 3b1, also known as the AT&T Unix PC (and the similar
AT&T 7300), has been removed.

=back

=head2 Platform-Specific Notes

XXX List any changes for specific platforms.  This could include configuration
and compilation changes or changes in portability/compatibility.  However,
changes within modules for platforms should generally be listed in the
L</Modules and Pragmata> section.

=over 4

=item WinCE

The building of XS modules has largely been restored.  Several still cannot
(yet) be built but it is now possible to build Perl on WinCE with only a couple
of further patches (to L<Socket> and L<ExtUtils::MakeMaker>), hopefully to be
incorporated soon.

=item GNU/Hurd

The BSD compatibility library C<libbsd> is no longer required for builds.

=back

=head1 Internal Changes

XXX Changes which affect the interface available to C<XS> code go here.  Other
significant internal changes for future core maintainers should be noted as
well.

[ List each change as a =item entry ]

=over 4

=item *

The internal representation has changed for the match variables $1, $2 etc.,
$`, $&, $', ${^PREMATCH}, ${^MATCH} and ${^POSTMATCH}.  It uses slightly less
memory, avoids string comparisons and numeric conversions during lookup, and
uses 23 fewer lines of C.  This change should not affect any external code.

=item *

Arrays now use NULL internally to represent unused slots, instead of
&PL_sv_undef.  &PL_sv_undef is no longer treated as a special value, so
av_store(av, 0, &PL_sv_undef) will cause element 0 of that array to hold a
read-only undefined scalar.  C<$array[0] = anything> will croak and
C<\$array[0]> will compare equal to C<\undef>.

=back

=head1 Selected Bug Fixes

XXX Important bug fixes in the core language are summarized here.  Bug fixes in
files in F<ext/> and F<lib/> are best summarized in L</Modules and Pragmata>.

[ List each fix as a =item entry ]

=over 4

=item *

The value of $^E is now saved across signal handlers on Windows.  [perl #85104]

=item *

A lexical filehandle (as in C<open my $fh...>) is usually given a name based on
the current package and the name of the variable, e.g. "main::$fh".  Under
recursion, the filehandle was losing the "$fh" part of the name.  This has been
fixed.

=item *

Perl 5.19.3 accidentally extended the previous bug to all closures, even when
not called recursively, i.e. lexical handles in closure would always be called
"main::" or "MyPackage::" etc.  This has been fixed.

=item *

Uninitialized values returned by XSUBs are no longer exempt from uninitialized
warnings.  [perl #118693]

=item *

C<elsif ("")> no longer erroneously produces a warning about void context.
[perl #118753]

=item *

Passing C<undef> to a subroutine now causes @_ to contain the same read-only
undefined scalar that C<undef> returns.  Furthermore, C<exists $_[0]> will now
return true if C<undef> was the first argument.  [perl #7508, #109726]

=item *

Passing a nonexistent array element to a subroutine does not usually autovivify
it unless the subroutine modifies its argument.  This did not work correctly
with negative indices and with nonexistent elements within the array.  The
element would be vivified immediately.  The delayed vivification has been
extended to work with those.  [perl #118691]

=item *

Assigning references or globs to the scalar returned by $#foo after the @foo
array has been freed no longer causes assertion failures on debugging builds
and memory leaks on regular builds.

=item *

Perl 5.19.2 threw line numbers off after some cases of line breaks following
keywords, such as

   1 unless
   1;

This has been fixed.  [perl #118931]

=item *

On 64-bit platforms, large ranges like 1..1000000000000 no longer crash, but
eat up all your memory instead.  [perl #119161]

=item *

C<__DATA__> now puts the C<DATA> handle in the right package, even if the
current package has been renamed through glob assignment.

=item *

The string position set by C<pos> could shift if the string changed
representation internally to or from utf8.  This could happen, e.g., with
references to objects with string overloading.

=item *

Taking references to the return values of two C<pos> calls with the same
argument, and then assigning a reference to one and C<undef> to the other,
could result in assertion failures or memory leaks.

=item *

Elements of @- and @+ now update correctly when they refer to nonexistent
captures.  Previously, a referenced element (C<$ref = \$-[1]>) could refer to
the wrong match after subsequent matches.

=item *

When C<die>, C<last>, C<next>, C<redo>, C<goto> and C<exit> unwind the scope,
it is possible for C<DESTROY> recursively to call a subroutine or format that
is currently being exited.  It that case, sometimes the lexical variables
inside the sub would start out having values from the outer call, instead of
being undefined as they should.  This has been fixed.  [perl #119311]

=item *

${^MPEN} is no longer treated as a synonym for ${^MATCH}.

=item *

Perl now tries a little harder to return the correct line number in
C<(caller)[2]>.  [perl #115768]

=item *

Line numbers inside multiline quote-like operators are now reported correctly.
[perl #3643]

=item *

C<#line> directives inside code embedded in quote-like operators are now
respected.

=item *

Line numbers are now correct inside the second here-doc when two here-doc
markers occur on the same line.

=item *

Starting with Perl 5.12, line numbers were off by one if the B<-d> switch was
used on the #! line.  Now they are correct.

=item *

Perl 5.19.2 inadvertently stopped some lines of code from being available to
the debugger if C<=E<gt>> occurred at the beginning of a line and the previous
line ended with a keyword.  This is now fixed.

=item *

Perl 5.19.2 allowed the PERL5DB environment variable to contain multiple lines
of code, but those lines were not made available to the debugger.  Now they are
all stuffed into line number 0, accessible via C<$dbline[0]> in the debugger.

=item *

An optimisation in Perl 5.18 made incorrect assumptions causing a bad
interaction with the L<Devel::CallParser> CPAN module.  If the module was
loaded then lexical variables declared in separate statements following a
C<my(...)> list might fail to be cleared on scope exit.

=item *

C<&xsub> and C<goto &xsub> calls now allow the called subroutine to autovivify
elements of @_.

=item *

C<&xsub> and C<goto &xsub> no longer crash if *_ has been undefined and has no
ARRAY entry (i.e. @_ does not exist).

=item *

C<&xsub> and C<goto &xsub> now work with tied @_.

=item *

Overlong identifiers no longer cause a buffer overflow (and a crash).  They
started doing so in Perl 5.18.

=item *

The warning "Scalar value @hash{foo} better written as $hash{foo}" now produces
far fewer false positives.  In particular, C<@hash{+function_returning_a_list}>
and C<@hash{ qw "foo bar baz" }> no longer warn.  The same applies to array
slices.  [perl #28380, #114024]

=back

=head1 Known Problems

XXX Descriptions of platform agnostic bugs we know we can't fix go here.  Any
tests that had to be C<TODO>ed for the release would be noted here.  Unfixed
platform specific bugs also go here.

[ List each fix as a =item entry ]

=over 4

=item *

XXX

=back

=head1 Obituary

XXX If any significant core contributor has died, we've added a short obituary
here.

=head1 Acknowledgements

XXX Generate this with:

  perl Porting/acknowledgements.pl v5.19.3..HEAD

=head1 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 L<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 C<perl -V>,
will be sent off to perlbug@perl.org to be analysed by the Perl porting team.

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

=head1 SEE ALSO

The F<Changes> file for an explanation of how to view exhaustive details on
what changed.

The F<INSTALL> file for how to build Perl.

The F<README> file for general stuff.

The F<Artistic> and F<Copying> files for copyright information.

=cut