=encoding utf8

=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 v5.15.0

=head1 DESCRIPTION

This document describes differences between the 5.15.0 release and
the 5.14.0 release.

If you are upgrading from an earlier release such as 5.YYY.YYY, first read
L<perl5YYYdelta>, which describes differences between 5.ZZZ.ZZZ and
5.YYY.YYY.

Some of the changes have been included in Perl 5.14.1.  These are
indicated with a "(5.14.1)" marker.

=head1 Notice

XXX Any important notices here

=head1 Core Enhancements

XXX New core language features go here. Summarise 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 ]

=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

[ List each incompatible change as a =head2 entry ]

=head1 Deprecations

XXX Any deprecated features, syntax, modules etc. should be listed here.
In particular, deprecated modules should be listed here even if they are
listed as an updated module in the L</Modules and Pragmata> section.

[ List each deprecation as a =head2 entry ]

=head1 Performance Enhancements

XXX Changes which enhance performance without changing behaviour go here. There
may well be none in a stable release.

[ List each enhancement as a =item entry ]

=over 4

=item *

XXX

=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<B> has been upgraded from version 1.29 to version 1.30.

=item *

L<B::Deparse> has been upgraded from version 1.03 to 1.05.

It addresses two regressions in Perl 5.14.0:

=over

=item *

Deparsing of the C<glob> operator and its diamond (C<< <> >>) form now
works again [RT #90898] (5.14.1).

=item *

The presence of subroutines named C<::::> or C<::::::> no longer causes
B::Deparse to hang (5.14.1).

=back

XXX Other Deparse fixes go here.

=item *

L<Devel::Peek> has been upgraded from version 1.07 to 1.08.

Its C<fill_mstats> function no longer refuses to write to copy-on-write
scalars.

=item *

L<Math::Complex> has been upgraded from version 1.56 to version 1.57.

Correct copy constructor usage.
Fix polarwise formatting with numeric format specifier.
More stable C<great_circle_direction> algorithm.

=item *

L<PerlIO::encoding> has been upgraded from version 0.14 to 0.15

=item *

L<PerlIO::scalar> has been upgraded from version 0.11 to 0.12.

It fixes a problem with C<< open my $fh, ">", \$scalar >> not working if
C<$scalar> is a copy-on-write scalar.

=item *

XXX If any changes are made, the version will need to be bumped again.
What blead has is currently (as of a9d1f3db, 7th of June) identical to
5.14.1's version.

L<Pod::Perldoc> has been upgraded from version 3.15_03 to 3.15_04.

It corrects the search paths on VMS [RT #90640].

=item *

L<Storable> has been upgraded from version 2.27 to version 2.28.

It no longer turns copy-on-write scalars into read-only scalars when
freezing and thawing.

=item *

L<Time::HiRes> has been upgraded from version 1.9721_01 to version 1.9722.

Portability fix, and avoiding some compiler warnings.

=item *

L<Module::CoreList> has been upgraded from version 2.49 to 2.50.

Updated for v5.12.4.

=item *

XXX

=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<perlfunc>

=over

=item *

C<given>, C<when> and C<default> are now listed in L<perlfunc> (5.14.1).

=back

=head3 L<perllol>

=over

=item *

L<perllol> has been expanded with examples using the new C<push $scalar>
syntax introduced in Perl 5.14.0 (5.14.1).

=back

=head3 L<perlop>

=over 4

=item *

The explanation of bitwise operators has been expanded to explain how they
work on Unicode strings (5.14.1).

=item *

The section on the triple-dot or yada-yada operator has been moved up, as
it used to separate two closely related sections about the comma operator
(5.14.1).

=item *

More examples for C<m//g> have been added (5.14.1).

=item *

The C<<< <<\FOO >>> here-doc syntax has been documented (5.14.1).

=back

=head3 L<perlrun>

=over

=item *

L<perlrun> has undergone a significant clean-up.  Most notably, the
B<-0x...> form of the B<-0> flag has been clarified, and the final section
on environment variables has been corrected and expanded (5.14.1).

=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.

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

=head2 New Diagnostics

XXX Newly added diagnostic messages go here

=over 4

=item *

Assigning to a temporary scalar returned from an XS lvalue subroutine now
produces a warning: "Useless assignment to a temporary".  This should help
PDL users [RT #31946].

=back

=head2 Changes to Existing Diagnostics

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

=over 4

=item *

XXX

=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<XXX>

=over 4

=item *

XXX

=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 *

F<regexp.h> has been modified for compatibility with GCC's B<-Werror>
option, as used by some projects that include perl's header files (5.14.1).

=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 summarising, although the bugs
that they represent may be covered elsewhere.

[ List each test improvement as a =item entry ]

=over 4

=item *

XXX

=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 XXX-some-platform

XXX

=back

=head2 Discontinued Platforms

XXX List any platforms that this version of perl no longer compiles on.

=over 4

=item XXX-some-platform

XXX

=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 XXX-some-platform

XXX

=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.

=over 4

=item *

The compiled representation of formats is now stored via the mg_ptr of
their PERL_MAGIC_fm. Previously it was stored in the string buffer,
beyond SvLEN(), the regular end of the string. SvCOMPILED() and
SvCOMPILED_{on,off}() now exist solely for compatibility for XS code.
The first is always 0, the other two now no-ops.

=back

=head1 Selected Bug Fixes

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

[ List each fix as a =item entry ]

=over 4

=item *

The new (in 5.14.0) regular expression modifier C</a> when repeated like
C</aa> forbids the characters outside the ASCII range that match
characters inside that range from matching under C</i>.  This did not
work under some circumstances, all involving alternation, such as:

 "\N{KELVIN SIGN}" =~ /k|foo/iaa;

succeeded inaprropriately.  This is now fixed.

=item *

5.14.0 introduced some memory leaks in regular expression character
classes such as C<[\w\s]>, which have now been fixed (5.14.1).

=item *

An edge case in regular expression matching could potentially loop.
This happened only under C</i> in bracketed character classes that have
characters with multi-character folds, and the target string to match
against includes the first portion of the fold, followed by another
character that has a multi-character fold that begins with the remaining
portion of the fold, plus some more.

 "s\N{U+DF}" =~ /[\x{DF}foo]/i

is one such case.  C<\xDF> folds to C<"ss"> (5.14.1).

=item *

A few characters in regular expression pattern matches did not
match correctly in some circumstances, all involving C</i>.  The
affected characters are:
COMBINING GREEK YPOGEGRAMMENI,
GREEK CAPITAL LETTER IOTA,
GREEK CAPITAL LETTER UPSILON,
GREEK PROSGEGRAMMENI,
GREEK SMALL LETTER IOTA WITH DIALYTIKA AND OXIA,
GREEK SMALL LETTER IOTA WITH DIALYTIKA AND TONOS,
GREEK SMALL LETTER UPSILON WITH DIALYTIKA AND OXIA,
GREEK SMALL LETTER UPSILON WITH DIALYTIKA AND TONOS,
LATIN SMALL LETTER LONG S,
LATIN SMALL LIGATURE LONG S T,
and
LATIN SMALL LIGATURE ST.

=item *

Formats: number of edge cases have been fixed with formats and formline;
in particular, where the format itself is potentially variable (such as
with ties and overloading), and where the format and data differ in their
encoding. In both these cases, it used to possible for the output to be
corrupted.

=item *

A bug has been fixed that would cause a "Use of freed value in iteration"
error if the next two hash elements that would be iterated over are
deleted [RT #85026] (5.14.1).

=item *

Passing the same constant subroutine to both C<index> and C<formline> no
longer causes one or the other to fail [RT #89218] (5.14.1).

=item *

XXX Someone tell me whether this first clause is correct (see commit
765f542d):

Copy-on-write scalars were introduced in 5.10.0.  These occur when
C<__PACKAGE__> or a hash key is a assigned to a scalar.  Several parts
of Perl were not updated to account for them, but have now been fixed:

=over

=item *

C<utf8::decode> had a nasty bug that would modify copy-on-write scalars'
string buffers in place (i.e., skipping the copy).  This could result in
hashes having two elements with the same key [RT #91834].

=item *

Lvalue subroutines were not allowing COW scalars to be returned.  This was
fixed for lvalue scalar context in Perl 5.12.3 and 5.14.0, but list context
was not fixed until this release.

=item *

Elements of restricted hashes (see the L<fields> pragma) containing
copy-on-write values couldn't be deleted, nor could such hashes be cleared
(C<%hash = ()>).

=item *

Localising a tied variable used to make it read-only if it contained a
copy-on-write string.

=item *

L<Storable>, L<Devel::Peek> and L<PerlIO::scalar> had similar problems.
See L</Updated Modules and Pragmata>, above.

=back

=item *

There have been various fixes to lvalue subroutines:

XXX Should these first three go under New Features?

=over

=item *

Explicit return now returns the actual argument passed to return, instead
of copying it [RT #72724].

=item *

Lvalue subroutines used to enforce lvalue syntax (i.e., whatever can go on
the left-hand side of C<=>) for the last statement and the arguments to
return.  Since lvalue subroutines are not always called in lvalue context,
this restriction has been lifted.

=item *

Lvalue subroutines are less restrictive as to what values can be returned.
It used to croak on values returned by C<shift> and C<delete> and from
other subroutines, but no longer does so.

=item *

Empty lvalue subroutines (C<sub :lvalue {}>) used to return C<@_> in list
context.  In fact, all subroutines used to, but regular subs were fixed in
Perl 5.8.2.  Now lvalue subroutines have been likewise fixed.

=item *

Lvalue subroutines used to copy their return values in rvalue context.  Not
only was this a waste of CPU cycles, but it also caused bugs.  A C<($)>
prototype would cause an lvalue sub to copy its return value [RT #62498],
and C<while(lvalue_sub() =~ m/.../g) { ... }> would loop endlessly
[RT #78680].

=item *

Autovivification now works on values returned from lvalue subroutines
[RT #7946].

=item *

XXX This entry is probably too sarcastic in its use of "inanities".  But
I'm too tired to think of a better wording.

When called in pass-by-reference context (e.g., subroutine arguments or a
list passed to C<for>), an lvalue subroutine returning arrays or hashes
used to bind the arrays (or hashes) to scalar variables--something that is
not supposed to happen.  This could result in "Bizzare copy of ARRAY"
errors or C<print> ignoring its arguments.  It also made inanities like
C<@{\$_}> "work".  This was fixed in 5.14.0 if an array were the first
thing returned from the subroutine (but not for C<$scalar, @array> or
hashes being returned).  Now a more general fix has been applied
[RT #23790].

=back

=item *

List assignment to lexical variables declared with attributes in the same
statement (C<my ($x,@y) : blimp = (72,94)>) stopped working in Perl 5.8.0.
It has now been fixed.

=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, unless
they were specific to a particular platform (see below).

This is a list of some significant unfixed bugs, which are regressions
from either 5.XXX.XXX or 5.XXX.XXX.

[ 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 The list of people to thank goes here.

=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 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