=encoding utf8

=head1 NAME

perldelta - what is new for perl v5.25.9

=head1 DESCRIPTION

This document describes differences between the 5.25.8 release and the 5.25.9
release.

If you are upgrading from an earlier release such as 5.25.7, first read
L<perl5258delta>, which describes differences between 5.25.7 and 5.25.8.

=head1 Core Enhancements

=head2 New regular expression modifier C</xx>

Specifying two C<x> characters to modify a regular expression pattern
does everything that a single one does, but additionally TAB and SPACE
characters within a bracketed character class are generally ignored and
can be added to improve readability, like
S<C</[ ^ A-Z d-f p-x ]/xx>>.  Details are at
L<perlre/E<sol>x and E<sol>xx>.

=head1 Deprecations

=head2 String delimiters that aren't stand-alone graphemes are now deprecated

In order for Perl to eventually allow string delimiters to be Unicode
grapheme clusters (which look like a single character, but may be
a sequence of several ones), we have to stop allowing a single char
delimiter that isn't a grapheme by itself.  These are unlikely to exist
in actual code, as they would typically display as attached to the
character in front of them.

=head1 Performance Enhancements

=over 4

=item *

A hash in boolean context is now sometimes faster, e.g.

    if (!%h) { ... }

This was already special-cased, but some cases were missed, and even the
ones which weren't have been improved.

=item *

Several other ops may now also be faster in boolean context.

=back

=head1 Modules and Pragmata

=head2 Updated Modules and Pragmata

=over 4

=item *

L<attributes> has been upgraded from version 0.28 to 0.29.

The deprecation message for the C<:unique> and C<:locked> attributes
now mention they will disappear in Perl 5.28.

=item *

L<B::Deparse> has been upgraded from version 1.39 to 1.40.

=item *

L<B::Xref> has been upgraded from version 1.05 to 1.06.

It now uses 3-arg C<open()> instead of 2-arg C<open()>. [perl #130122]

=item *

L<Compress::Raw::Bzip2> has been upgraded from version 2.069 to 2.070.

=item *

L<Compress::Raw::Zlib> has been upgraded from version 2.069 to 2.070.

=item *

L<CPAN> has been upgraded from version 2.14_01 to 2.16.

=item *

L<Data::Dumper> was upgraded from version 2.166 to 2.167.

This fixes a stack management bug. [perl #130487].

=item *

L<DB_File> has been upgraded from version 1.838 to 1.840.

=item *

L<Devel::SelfStubber> has been upgraded from version 1.05 to 1.06.

It now uses 3-arg C<open()> instead of 2-arg C<open()>. [perl #130122]

=item *

L<diagnostics> has been upgraded from version 1.35 to 1.36.

It now uses 3-arg C<open()> instead of 2-arg C<open()>. [perl #130122]

=item *

L<DynaLoader> has been upgraded from version 1.40 to 1.41.

=item *

L<Errno> has been upgraded from version 1.27 to 1.28.

It now uses 3-arg C<open()> instead of 2-arg C<open()>. [perl #130122]

=item *

L<ExtUtils::Embed> has been upgraded from version 1.33 to 1.34.

It now uses 3-arg C<open()> instead of 2-arg C<open()>. [perl #130122]

=item *

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

Fixes the Unicode Bug in the range operator.

=item *

L<File::Glob> has been upgraded from version 1.27 to 1.28.

Issue a deprecation message for C<File::Glob::glob()>.

=item *

L<I18N::LangTags> has been upgraded from version 0.41 to 0.42.

It now uses 3-arg C<open()> instead of 2-arg C<open()>. [perl #130122]

=item *

L<lib> has been upgraded from version 0.63 to 0.64.

It now uses 3-arg C<open()> instead of 2-arg C<open()>. [perl #130122]

=item *

L<Module::CoreList> has been upgraded from version 5.20161220 to 5.20170120.

=item *

L<OS2::Process> has been upgraded from version 1.11 to 1.12.

It now uses 3-arg C<open()> instead of 2-arg C<open()>. [perl #130122]

=item *

L<overload> has been upgraded from version 1.27 to 1.28.

=item *

L<perl5db.pl> has been upgraded from version 1.50 to 1.51.

Ignore F</dev/tty> on non-Unix systems. [perl #113960]

=item *

L<PerlIO::scalar> has been upgraded from version 0.25 to 0.26.

=item *

L<Pod::Html> has been upgraded from version 1.2201 to 1.2202.

=item *

L<re> has been upgraded from version 0.33 to 0.34

This adds support for the new L<C<E<47>xx>|perlre/E<sol>x and E<sol>xx>
regular expression pattern modifier, and a change to the L<S<C<use re
'strict'>>|re/'strict' mode> experimental feature.  When S<C<re
'strict'>> is enabled, a warning now will be generated for all
unescaped uses of the two characters C<}> and C<]> in regular
expression patterns (outside bracketed character classes) that are taken
literally.  This brings them more in line with the C<)> character which
is always a metacharacter unless escaped.  Being a metacharacter only
sometimes, depending on action at a distance, can lead to silently
having the pattern mean something quite different than was intended,
which the S<C<re 'strict'>> mode is intended to minimize.

=item *

L<Storable> has been upgraded from version 2.59 to 2.61.

Fixes [perl #130098].

=item *

L<Symbol> has been upgraded from version 1.07 to 1.08.

=item *

L<Term::ReadLine> has been upgraded from version 1.15 to 1.16.

It now uses 3-arg C<open()> instead of 2-arg C<open()>. [perl #130122]

=item *

L<Test> has been upgraded from version 1.29 to 1.30.

It now uses 3-arg C<open()> instead of 2-arg C<open()>. [perl #130122]

=item *

L<threads> has been upgraded from version 2.10 to 2.12.

Fixes [perl #130469].

=item *

L<threads::shared> has been upgraded from version 1.52 to 1.54.

This fixes [cpan #119529], [perl #130457]

=item *

L<Unicode::UCD> has been upgraded from version 0.67 to 0.68.

It now uses 3-arg C<open()> instead of 2-arg C<open()>. [perl #130122]

=item *

L<VMS::DCLsym> has been upgraded from version 1.07 to 1.08.

It now uses 3-arg C<open()> instead of 2-arg C<open()>. [perl #130122]

=item *

L<XSLoader> has been upgraded from version 0.24 to 0.26.

It now uses 3-arg C<open()> instead of 2-arg C<open()>. [perl #130122]

=back

=head1 Documentation

=head2 New Documentation

=head3 L<perldeprecation>

This file documents all upcoming deprecations, and some of the deprecations
which already have been removed. The purpose of this documentation is
two-fold: document what will disappear, and by which version, and serve
as a guide for people dealing with code which has features that no longer
work after an upgrade of their perl.

=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>.

=head2 New Diagnostics

=head3 New Warnings

=over 4

=item *

L<Use of unassigned code point or non-standalone grapheme for a delimiter will be a fatal error starting in Perl v5.30|perldiag/"Use of unassigned code point or non-standalone grapheme for a delimiter will be a fatal error starting in Perl v5.30">

See L</Deprecations>

=back

=head2 Changes to Existing Diagnostics

As of Perl 5.25.9, all new deprecations will come with a version in
which the feature will disappear. And with a few exceptions, most
existing deprecations will state when they'll disappear. As such, most
deprecation messages have changed.

=over 4

=item *

Attribute "locked" is deprecated, and will disappear in Perl 5.28

=item *

Attribute "unique" is deprecated, and will disappear in Perl 5.28

=item *

"\c%c" is more clearly written simply as "%s". This will be a fatal error
in Perl 5.28

=item *

Constants from lexical variables potentially modified elsewhere are
deprecated. This will not be allowed in Perl 5.32

=item *

Deprecated use of my() in false conditional. This will be a fatal error
in Perl 5.30

=item *

dump() better written as CORE::dump(). dump() will no longer be available 
in Perl 5.30

=item *

${^ENCODING} is no longer supported. Its use will be fatal in Perl 5.28

=item *

File::Glob::glob() will disappear in perl 5.30. Use File::Glob::bsd_glob()
instead.

=item *

%s() is deprecated on :utf8 handles. This will be a fatal error in Perl 5.30

=item *

$* is no longer supported. Its use will be fatal in Perl 5.30

=item *

$* is no longer supported. Its use will be fatal in Perl 5.30

=item *

Opening dirhandle %s also as a file. This will be a fatal error in Perl 5.28

=item *

Opening filehandle %s also as a directory. This will be a fatal
error in Perl 5.28

=item *

Setting $/ to a reference to %s as a form of slurp is deprecated,
treating as undef. This will be fatal in Perl 5.28

=item *

Unescaped left brace in regex is deprecated here (and will be fatal
in Perl 5.30), passed through in regex; marked by S<< E<lt>-- HERE >> in m/%s/

=item *

Unknown charname '' is deprecated. Its use will be fatal in Perl 5.28

=item *

Use of bare E<lt>E<lt> to mean E<lt>E<lt>"" is deprecated. Its use will be fatal in Perl 5.28

=item *

Use of code point 0x%s is deprecated; the permissible max is 0x%s.
This will be fatal in Perl 5.28

=item *

Use of comma-less variable list is deprecated. Its use will be fatal
in Perl 5.28

=item *

Use of inherited AUTOLOAD for non-method %s() is deprecated. This
will be fatal in Perl 5.28

=item * 

Use of strings with code points over 0xFF as arguments to %s operator
is deprecated. This will be a fatal error in Perl 5.28

=back

=head1 Utility Changes

=head2 F<c2ph> and F<pstruct>

=over 4

=item *

These old utilities have long since superceded by L<h2xs>, and are
now gone from the distribution.

=back

=head2 F<Porting/sync-with-cpan>

=over 4

=item *

Many improvements

=back


=head1 Configuration and Compilation

=over 4

=item *

The C<dtrace> build process has further changes:

=over

=item *

If the C<-xnolibs> is available, use that so a F<dtrace> perl can be
built within a FreeBSD jail.

=item *

On systems that build a dtrace object file (FreeBSD, Solaris and
SystemTap's dtrace emulation), copy the input objects to a separate
directory and process them there, and use those objects in the link,
since C<dtrace -G> also modifies these objects.

=item *

Add libelf to the build on FreeBSD 10.x, since dtrace adds references
to libelf symbols.

=item *

Generate a dummy dtrace_main.o if C<dtrace -G> fails to build it.  A
default build on Solaris generates probes from the unused inline
functions, while they don't on FreeBSD, which causes C<dtrace -G> to
fail.

=back

[perl #130108]

=item *

You can now disable perl's use of the PERL_HASH_SEED and
PERL_PERTURB_KEYS environment variables by configuring perl with
C<-Accflags=NO_PERL_HASH_ENV>.

=item *

You can now disable perl's use of the PERL_HASH_SEED_DEBUG environment
variable by configuring perl with
C<-Accflags=-DNO_PERL_HASH_SEED_DEBUG>.

=back

=head1 Internal Changes

=over 4

=item *

New versions of macros like C<isALPHA_utf8> and C<toLOWER_utf8>  have
been added, each with the
suffix C<_safe>, like C<isSPACE_utf8_safe>.  These take an extra
parameter, giving an upper limit of how far into the string it is safe
to read.  Using the old versions could cause attempts to read beyond the
end of the input buffer if the UTF-8 is not well-formed, and their use
now raises a deprecation warning.  Details are at
L<perlapi/Character classification>.

=item *

Calling macros like C<isALPHA_utf8> on malformed UTF-8 have issued a
deprecation warning since Perl v5.18.  They now die.
Similarly, macros like C<toLOWER_utf8> on malformed UTF-8 now die.

=item *

Calling the functions C<utf8n_to_uvchr> and its derivatives, while
passing a string length of 0 is now asserted against in DEBUGGING
builds, and otherwise returns the Unicode REPLACEMENT CHARACTER.   If
you have nothing to decode, you shouldn't call the decode function.

=item *

The functions C<utf8n_to_uvchr> and its derivatives now return the
Unicode REPLACEMENT CHARACTER if called with UTF-8 that has the overlong
malformation, and that malformation is allowed by the input parameters.
This malformation is where the UTF-8 looks valid syntactically, but
there is a shorter sequence that yields the same code point.  This has
been forbidden since Unicode version 3.1.

=item *

The functions C<utf8n_to_uvchr> and its derivatives now accept an input
flag to allow the overflow malformation.  This malformation is when the
UTF-8 may be syntactically valid, but the code point it represents is
not capable of being represented in the word length on the platform.
What "allowed" means in this case is that the function doesn't return an
error, and advances the parse pointer to beyond the UTF-8 in question,
but it returns the Unicode REPLACEMENT CHARACTER as the value of the
code point (since the real value is not representable).

=back

=head1 Selected Bug Fixes

=over 4

=item *

Under C<use utf8>, the entire Perl program is now checked that the UTF-8
is wellformed.  This resolves [perl #126310].

=item *

The range operator C<..> on strings now handles its arguments correctly when in
the scope of the L<< C<unicode_strings>|feature/"The 'unicode_strings' feature" >>
feature. The previous behaviour was sufficiently unexpected that we believe no
correct program could have made use of it.

=item *

The S<split> operator did not ensure enough space was allocated for
its return value in scalar context.  It could then write a single
pointer immediately beyond the end of the memory block allocated for
the stack.  [perl #130262]

=item *

Using a large code point with the C<W> pack template character with
the current output position aligned at just the right point could
cause a write a single zero byte immediately beyond the end of an
allocated buffer.  [perl #129149]

=item *

Supplying the form picture argument as part of the form argument list
where the picture specifies modifying the argument could cause an
access to the new freed compiled form.  [perl #129125]

=item *

Fix a problem with sort's build-in compare, where it would not sort
correctly with 64-bit integers, and non-long doubles. [perl #130335]

=item *

Fix issues with /(?{ ... E<lt>E<lt>EOF })/ that broke Method-Signatures. [perl #130398]

=item * 

Fix a macro which caused syntax error on an EBCDIC build.

=item *

Prevent tests from getting hung up on 'NonStop' option. [perl #130445]

=item *

Fixed an assertion failure with C<chop> and C<chomp>, which
could be triggered by C<chop(@x =~ tr/1/1/)>. [perl #130198].

=item *

Fixed a comment skipping error under C</x>; it could stop skipping a
byte early, which could be in the middle of a UTF-8 character.
[perl #130495].

=item *

F<perldb> now ignores F</dev/tty> on non-Unix systems. [perl #113960];

=item *

Fix assertion failure for C<{}-E<gt>$x> when C<$x> isn't defined. [perl #130496].

=item *

DragonFly BSD now has support for setproctitle(). [perl #130068].

=item *

Fix an assertion error which could be triggered when lookahead string
in patterns exceeded a minimum length. [perl #130522].

=item *

Only warn once per literal about a misplaced C<_>. [perl #70878].

=item *

Ensure range-start is set after error in C<tr///>. [perl #129342].

=item *

Don't read past start of string for unmatched backref; otherwise,
we may have heap buffer overflow. [perl #129377].

=item *

Properly recognize mathematical digit ranges starting at U+1D7E. 
C<use re 'strict'> is supposed to warn if you use a range whose start
and end digit aren't from the same group of 10. It didn't do that
for five groups of mathematical digits starting at U+1D7E.

=back


=head1 Acknowledgements

Perl 5.25.9 represents approximately 4 weeks of development since Perl 5.25.8
and contains approximately 24,000 lines of changes across 400 files from 23
authors.

Excluding auto-generated files, documentation and release tools, there were
approximately 17,000 lines of changes to 220 .pm, .t, .c and .h files.

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 5.25.9:

Aaron Crane, Abigail, Andreas König, Andy Lester, Aristotle Pagaltzis
Chris 'BinGOs' Williams, Craig A. Berry, Dagfinn Ilmari Mannsåker, Dan Collins,
David Mitchell, Father Chrysostomos, Hugo van der Sanden, James E Keenan,
Jerry D. Hedden, John Lightsey, Karl Williamson, Paul Marquess, Peter Avalos,
Sawyer X, Steve Hay, Tomasz Konojacki, Tony Cook, Zefram.

The list above is almost certainly incomplete as it is automatically generated
from version control history. In particular, it does not include the names of
the (very much appreciated) contributors who reported issues to the Perl bug
tracker.

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.

For a more complete list of all of Perl's historical contributors, please see
the F<AUTHORS> file in the Perl source distribution.

=head1 Reporting Bugs

If you find what you think is a bug, you might check the perl bug database
at L<https://rt.perl.org/> .  There may also be information at
L<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 see
L<perlsec/SECURITY VULNERABILITY CONTACT INFORMATION>
for details of how to report the issue.

=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
