[p5sagit/p5-mst-13.2.git] / pod / perl5112delta.pod

=head1 NAME

[ Any text flagged as XXX needs to be processed before release. ]

perldelta - what is new for perl v5.11.2

=head1 DESCRIPTION

This document describes differences between the 5.11.1 release and
the 5.11.2 release.

=head1 Notice

XXX Unlikely to need this section.

=head1 Incompatible Changes

=head2 Use of C<:=> to mean an empty attribute list is now deprecated.

An accident of Perl's parser means that these constructions are all equivalent:

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

with the C<:> being treated as the start of an attribute list, which ends
before the C<=>. 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 means that C<:=> 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) the
avoid the warning by adding a space before the C<=>.

=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.

=head2 qr overloading

It is now possible to overload the C<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 C<=~> operator, or when it is
interpolated into a regexp. See L<overload>.

=head2 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 allow
a completely non-Perl sublanguage to be parsed inline, with the right
ops cleanly generated.  This feature is currently considered experimental.

See L<perlapi/PL_keyword_plugin> for the mechanism.  The Perl core source
distribution also includes a new module L<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.

=head2 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.

=head2 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 C<&> sigil.)

=head1 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.

=head1 Modules and Pragmata

XXX All changes to installed files in F<cpan/>, F<dist/>, F<ext/> and F<lib/>
go here, in a list ordered by distribution name. Minimally it should be the
module version, but it's more useful to the end user to give a paragraph's
summary of the module's changes. In an ideal world, dual-life modules would
have a F<Changes> file that could be cribbed.

=head2 New Modules and Pragmata

=over 4

=item C<XXX>

XXX

=back

=head2 Pragmata Changes

=over 4

=item C<XXX>

XXX

=back

=head2 Updated Modules

=over 4

=item C<XXX>

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>.

=over 4

=item F<XXX>

XXX

=back

=head1 New Documentation

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

=over 4

=item L<XXX>

XXX

=back

=head1 Changes to Existing Documentation

XXX Changes which significantly change existing files in F<pod/> go here.
Any changes to F<pod/perldiag.pod> should go in L</New or Changed Diagnostics>.


=head1 Performance Enhancements

=over 4

=item *

Reversing an array to itself (as in C<@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 C<EXISTS> and C<DELETE> methods.

=back

=head1 Installation and Configuration Improvements

XXX Changes to F<Configure>, F<installperl>, F<installman>, and analogous tools
go here.

=head2 Configuration improvements

XXX

=head2 Compilation improvements

XXX

=head2 Platform Specific Changes

=over 4

=item XXX-some-platform

XXX

=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>.

=over 4

=item *

XXX

=back

=head1 New or Changed Diagnostics

XXX New or changed warnings emitted by the core's C<C> code go here.

=over 4

=item C<XXX>

XXX

=back

=head1 Changed Internals

=over 4

=item *

C<Perl_pmflag> has been removed from the 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
F<toke.c>, and prior to 5.10, F<regcomp.c>. In core, it has been replaced by a
static function.

=back

=head1 New Tests

XXX Changes which create B<new> files in F<t/> go here. Changes to
existing files in F<t/> aren't worth summarising, although the bugs that
they represent may be.

=over 4

=item F<XXX>

XXX

=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 5.10.1 or 5.11.1.

=over 4

=item *

XXX

=back

=head1 Deprecations

XXX Add any new known deprecations here.

The following items are now deprecated.

=over 4

=item *

XXX

=back

=head1 Platform Specific Notes

XXX Any changes specific to a particular platform. VMS and Win32 are the usual
stars here. It's probably best to group changes under the same section layout
as the main perldelta

=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 B<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
Commit	Line	Data
d5114285	1	=head1 NAME
	2
	3	[ Any text flagged as XXX needs to be processed before release. ]
	4
	5	perldelta - what is new for perl v5.11.2
	6
	7	=head1 DESCRIPTION
	8
	9	This document describes differences between the 5.11.1 release and
	10	the 5.11.2 release.
	11
	12	=head1 Notice
	13
	14	XXX Unlikely to need this section.
	15
	16	=head1 Incompatible Changes
	17
d83f38d8	18	=head2 Use of C<:=> to mean an empty attribute list is now deprecated.
d5114285	19
d83f38d8	20	An accident of Perl's parser means that these constructions are all equivalent:
d5114285	21
d83f38d8	22	my $pi := 4;
	23	my $pi : = 4;
	24	my $pi : = 4;
	25
	26	with the C<:> being treated as the start of an attribute list, which ends
	27	before the C<=>. As whitespace is not significant here, all are parsed as an
	28	empty attribute list, hence all the above are equivalent to, and better written
	29	as
	30
	31	my $pi = 4;
	32
	33	because no attribute processing is done for an empty list.
	34
	35	As is, this means that C<:=> cannot be used as a new token, without silently
	36	changing the meaning of existing code. Hence that particular form is now
	37	deprecated, and will become a syntax error. If it is absolutely necessary to
	38	have empty attribute lists (for example, because of a code generator) the
	39	avoid the warning by adding a space before the C<=>.
d5114285	40
	41	=head1 Core Enhancements
	42
	43	XXX New core language features go here. Summarise user-visible core language
	44	enhancements. Particularly prominent performance optimisations could go
	45	here, but most should go in the L</Performance Enhancements> section.
	46
97352077	47	=head2 qr overloading
	48
	49	It is now possible to overload the C<qr//> operator, that is, conversion
	50	to regexp, like it was already possible to overload conversion to
	51	boolean, string or number of objects. It is invoked when an object
	52	appears on the right hand side of the C<=~> operator, or when it is
	53	interpolated into a regexp. See L<overload>.
	54
88e1f1a2	55	=head2 Pluggable keywords
	56
	57	Extension modules can now cleanly hook into the Perl parser to define new
	58	kinds of keyword-headed expression and compound statement. The syntax
	59	following the keyword is defined entirely by the extension. This allow
	60	a completely non-Perl sublanguage to be parsed inline, with the right
580561a3	61	ops cleanly generated. This feature is currently considered experimental.
88e1f1a2	62
	63	See L<perlapi/PL_keyword_plugin> for the mechanism. The Perl core source
	64	distribution also includes a new module L<XS::APItest::KeywordRPN>, which
	65	implements reverse Polish notation arithmetic via pluggable keywords.
	66	This module is mainly used for test purposes, and is not normally
	67	installed, but also serves as an example of how to use the new mechanism.
	68
580561a3	69	=head2 APIs for more internals
	70
	71	The lowest layers of the lexer and parts of the pad system now have C
	72	APIs available to XS extensions. These are necessary to support proper
	73	use of pluggable keywords, but have other uses too. The new APIs are
	74	experimental, and only cover a small proportion of what would be necessary
	75	to take full advantage of the core's facilities in these areas. It is
	76	intended that the Perl 5.13 development cycle will see the addition of
	77	a full range of clean, supported interfaces.
	78
f7461760	79	=head2 Overridable function lookup
	80
	81	Where an extension module hooks the creation of rv2cv ops, to modify
	82	the subroutine lookup process, this now works correctly for bareword
	83	subroutine calls. This means that prototypes on subroutines referenced
	84	this way will be processed correctly. (Previously bareword subroutine
	85	names were initially looked up, for parsing purposes, by an unhookable
	86	mechanism, so extensions could only properly influence subroutine names
	87	that appeared with an C<&> sigil.)
	88
d5114285	89	=head1 New Platforms
	90
	91	XXX List any platforms that this version of perl compiles on, that previous
	92	versions did not. These will either be enabled by new files in the F<hints/>
	93	directories, or new subdirectories and F<README> files at the top level of the
	94	source tree.
	95
	96	=head1 Modules and Pragmata
	97
	98	XXX All changes to installed files in F<cpan/>, F<dist/>, F<ext/> and F<lib/>
	99	go here, in a list ordered by distribution name. Minimally it should be the
	100	module version, but it's more useful to the end user to give a paragraph's
	101	summary of the module's changes. In an ideal world, dual-life modules would
	102	have a F<Changes> file that could be cribbed.
	103
	104	=head2 New Modules and Pragmata
	105
	106	=over 4
	107
	108	=item C<XXX>
	109
	110	XXX
	111
	112	=back
	113
	114	=head2 Pragmata Changes
	115
	116	=over 4
	117
	118	=item C<XXX>
	119
	120	XXX
	121
	122	=back
	123
	124	=head2 Updated Modules
	125
	126	=over 4
	127
	128	=item C<XXX>
	129
	130	XXX
	131
	132	=back
	133
	134	=head1 Utility Changes
	135
	136	XXX Changes to installed programs such as F<perlbug> and F<xsubpp> go
	137	here. Most of these are built within the directories F<utils> and F<x2p>.
	138
	139	=over 4
	140
	141	=item F<XXX>
	142
	143	XXX
	144
	145	=back
	146
	147	=head1 New Documentation
	148
	149	XXX Changes which create B<new> files in F<pod/> go here.
	150
	151	=over 4
	152
153	=item L<XXX>
154
155	XXX
156
157	=back
158
159	=head1 Changes to Existing Documentation
160
161	XXX Changes which significantly change existing files in F<pod/> go here.
162	Any changes to F<pod/perldiag.pod> should go in L</New or Changed Diagnostics>.
163
164
165	=head1 Performance Enhancements
166
d5114285	167	=over 4
	168
	169	=item *
	170
437d4214	171	Reversing an array to itself (as in C<@a = reverse @a>) in void context now
	172	happens in-place and is several orders of magnitude faster than it used to be.
	173	It will also preserve non-existent elements whenever possible, i.e. for non
	174	magical arrays or tied arrays with C<EXISTS> and C<DELETE> methods.
d5114285	175
	176	=back
	177
	178	=head1 Installation and Configuration Improvements
	179
	180	XXX Changes to F<Configure>, F<installperl>, F<installman>, and analogous tools
	181	go here.
	182
	183	=head2 Configuration improvements
	184
	185	XXX
	186
	187	=head2 Compilation improvements
	188
	189	XXX
	190
	191	=head2 Platform Specific Changes
	192
	193	=over 4
	194
	195	=item XXX-some-platform
	196
	197	XXX
	198
	199	=back
	200
	201	=head1 Selected Bug Fixes
	202
	203	XXX Important bug fixes in the core language are summarised here.
	204	Bug fixes in files in F<ext/> and F<lib/> are best summarised in
	205	L</Modules and Pragmata>.
	206
	207	=over 4
	208
	209	=item *
	210
	211	XXX
	212
	213	=back
	214
	215	=head1 New or Changed Diagnostics
	216
	217	XXX New or changed warnings emitted by the core's C<C> code go here.
	218
	219	=over 4
	220
	221	=item C<XXX>
	222
	223	XXX
	224
	225	=back
	226
	227	=head1 Changed Internals
	228
d5114285	229	=over 4
	230
	231	=item *
	232
879d0c72	233	C<Perl_pmflag> has been removed from the public API. Calling it now generates
	234	a deprecation warning, and it will be removed in a future release. Although
	235	listed as part of the API, it was never documented, and only ever used in
	236	F<toke.c>, and prior to 5.10, F<regcomp.c>. In core, it has been replaced by a
	237	static function.
d5114285	238
	239	=back
	240
	241	=head1 New Tests
	242
	243	XXX Changes which create B<new> files in F<t/> go here. Changes to
	244	existing files in F<t/> aren't worth summarising, although the bugs that
	245	they represent may be.
	246
	247	=over 4
	248
	249	=item F<XXX>
	250
	251	XXX
	252
	253	=back
	254
	255	=head1 Known Problems
	256
	257	XXX Descriptions of platform agnostic bugs we know we can't fix go here. Any
	258	tests that had to be C<TODO>ed for the release would be noted here, unless
	259	they were specific to a particular platform (see below).
	260
	261	This is a list of some significant unfixed bugs, which are regressions
	262	from either 5.10.1 or 5.11.1.
	263
	264	=over 4
	265
	266	=item *
	267
	268	XXX
	269
	270	=back
	271
	272	=head1 Deprecations
	273
	274	XXX Add any new known deprecations here.
	275
	276	The following items are now deprecated.
	277
	278	=over 4
	279
	280	=item *
	281
	282	XXX
	283
	284	=back
	285
	286	=head1 Platform Specific Notes
	287
	288	XXX Any changes specific to a particular platform. VMS and Win32 are the usual
	289	stars here. It's probably best to group changes under the same section layout
	290	as the main perldelta
	291
	292	=head1 Obituary
	293
	294	XXX If any significant core contributor has died, we've added a short obituary
	295	here.
	296
	297	=head1 Acknowledgements
	298
	299	XXX The list of people to thank goes here.
	300
	301
302	=head1 Reporting Bugs
303
304	If you find what you think is a bug, you might check the articles
305	recently posted to the comp.lang.perl.misc newsgroup and the perl
306	bug database at http://rt.perl.org/perlbug/ . There may also be
307	information at http://www.perl.org/ , the Perl Home Page.
308
309	If you believe you have an unreported bug, please run the B<perlbug>
310	program included with your release. Be sure to trim your bug down
311	to a tiny but sufficient test case. Your bug report, along with the
312	output of C<perl -V>, will be sent off to perlbug@perl.org to be
313	analysed by the Perl porting team.
314
315	If the bug you are reporting has security implications, which make it
316	inappropriate to send to a publicly archived mailing list, then please send
317	it to perl5-security-report@perl.org. This points to a closed subscription
318	unarchived mailing list, which includes all the core committers, who be able
319	to help assess the impact of issues, figure out a resolution, and help
320	co-ordinate the release of patches to mitigate or fix the problem across all
321	platforms on which Perl is supported. Please only use this address for
322	security issues in the Perl core, not for modules independently
323	distributed on CPAN.
324
325	=head1 SEE ALSO
326
327	The F<Changes> file for an explanation of how to view exhaustive details
328	on what changed.
329
330	The F<INSTALL> file for how to build Perl.
331
332	The F<README> file for general stuff.
333
334	The F<Artistic> and F<Copying> files for copyright information.
335
336	=cut