[p5sagit/p5-mst-13.2.git] / pod / perl595delta.pod

=head1 NAME

perldelta - what is new for perl v5.9.5

=head1 DESCRIPTION

This document describes differences between the 5.9.4 and the 5.9.5
development releases. See L<perl590delta>, L<perl591delta>,
L<perl592delta>, L<perl593delta> and L<perl594delta> for the differences
between 5.8.0 and 5.9.4.

=head1 Incompatible Changes

=head2 Tainting and printf

When perl is run under taint mode, C<printf()> and C<sprintf()> will now
reject any tainted format argument.

=head2 Removal of the bytecode compiler and of perlcc

C<perlcc>, the byteloader and the supporting modules (B::C, B::CC,
B::Bytecode, etc.) are no longer distributed with the perl sources. Those
experimental tools have never worked reliably, and, due to the lack of
volunteers to keep them in line with the perl interpreter developments, it
was decided to remove them instead of shipping a broken version of those.
The last version of those modules can be found with perl 5.9.4.

However the B compiler framework stays supported in the perl core, as with
the more useful modules it has permitted (among others, B::Deparse and
B::Concise).

=head2 Removal of the JPL

The JPL (Java-Perl Linguo) has been removed from the perl sources tarball.

=head1 Core Enhancements

=head2 Regular expressions

=over 4

=item Recursive Patterns

It is now possible to write recursive patterns without using the C<(??{})>
construct. This new way is more efficient, and in many cases easier to
read.

Each capturing parenthesis can now be treated as an independent pattern
that can be entered by using the C<(?PARNO)> syntax (C<PARNO> standing for
"parenthesis number"). For example, the following pattern will match
nested balanced angle brackets:

    /
     ^                      # start of line
     (                      # start capture buffer 1
	<                   #   match an opening angle bracket
	(?:                 #   match one of:
	    (?>             #     don't backtrack over the inside of this group
		[^<>]+      #       one or more non angle brackets
	    )               #     end non backtracking group
	|                   #     ... or ...
	    (?1)            #     recurse to bracket 1 and try it again
	)*                  #   0 or more times.
	>                   #   match a closing angle bracket
     )                      # end capture buffer one
     $                      # end of line
    /x

Note, users experienced with PCRE will find that the Perl implementation
of this feature differs from the PCRE one in that it is possible to
backtrack into a recursed pattern, whereas in PCRE the recursion is
atomic or "possessive" in nature. (Yves Orton)

=item Named Capture Buffers

It is now possible to name capturing parenthesis in a pattern and refer to
the captured contents by name. The naming syntax is C<< (?<NAME>....) >>.
It's possible to backreference to a named buffer with the C<< \k<NAME> >>
syntax. In code, the new magical hash C<%+> can be used to access the
contents of the buffers.

Thus, to replace all doubled chars, one could write

    s/(?<letter>.)\k<letter>/$+{letter}/g

Only buffers with defined contents will be "visible" in the hash, so
it's possible to do something like

    foreach my $name (keys %+) {
        print "content of buffer '$name' is $+{$name}\n";
    }

Users exposed to the .NET regex engine will find that the perl
implementation differs in that the numerical ordering of the buffers
is sequential, and not "unnamed first, then named". Thus in the pattern

   /(A)(?<B>B)(C)(?<D>D)/

$1 will be 'A', $2 will be 'B', $3 will be 'C' and $4 will be 'D' and not
$1 is 'A', $2 is 'C' and $3 is 'B' and $4 is 'D' that a .NET programmer
would expect. This is considered a feature. :-) (Yves Orton)

=item Possessive Quantifiers

Perl now supports the "possessive quantifier" syntax of the "atomic match" 
pattern. Basically a possessive quantifier matches as much as it can and never
gives any back. Thus it can be used to control backtracking. The syntax is 
similar to non-greedy matching, except instead of using a '?' as the modifier
the '+' is used. Thus C<?+>, C<*+>, C<++>, C<{min,max}+> are now legal
quantifiers. (Yves Orton)

=item Backtracking control verbs

The regex engine now supports a number of special purpose backtrack
control verbs: (*COMMIT), (*MARK), (*CUT), (*ERROR), (*FAIL) and
(*ACCEPT). See L<perlre> for their descriptions.

=back

=head2 The C<_> prototype

A new prototype character has been added. C<_> is equivalent to C<$> (it
denotes a scalar), but defaults to C<$_> if the corresponding argument
isn't supplied. Due to the optional nature of the argument, you can only
use it at the end of a prototype, or before a semicolon.

This has a small incompatible consequence: the prototype() function has
been adjusted to return C<_> for some built-ins in appropriate cases (for
example, C<prototype('CORE::rmdir')>). (Rafael Garcia-Suarez)

=head2 UNITCHECK blocks

C<UNITCHECK>, a new special code block has been introduced, in addition to
C<BEGIN>, C<CHECK>, C<INIT> and C<END>.

C<CHECK> and C<INIT> blocks, while useful for some specialized purposes,
are always executed at the transition between the compilation and the
execution of the main program, and thus are useless whenever code is
loaded at runtime. On the other hand, C<UNITCHECK> blocks are executed
just after the unit which defined them has been compiled. See L<perlmod>
for more information. (Alex Gough)

=head2 UCD 5.0.0

The copy of the Unicode Character Database included in Perl 5.9 has
been updated to version 5.0.0.

=head1 Modules and Pragmas

=head2 New Core Modules

=over 4

=item *

C<Locale::Maketext::Simple>, needed by CPANPLUS, is a simple wrapper around
C<Locale::Maketext::Lexicon>. Note that C<Locale::Maketext::Lexicon> isn't
included in the perl core; the behaviour of C<Locale::Maketext::Simple>
gracefully degrades when the later isn't present.

=item *

C<Params::Check> implements a generic input parsing/checking mechanism. It
is used by CPANPLUS.

=back

=head2 Module changes

=over 4

=item C<base>

The C<base> pragma now warns if a class tries to inherit from itself.

=item C<warnings>

The C<warnings> pragma doesn't load C<Carp> anymore. That means that code
that used C<Carp> routines without having loaded it at compile time might
need to be adjusted; typically, the following (faulty) code won't work
anymore, and will require parentheses to be added after the function name:

    use warnings;
    require Carp;
    Carp::confess "argh";

=back

=head1 Utility Changes

=head1 Documentation

=head1 Performance Enhancements

=head1 Installation and Configuration Improvements

=head2 C++ compatibility

Efforts have been made to make perl and the core XS modules compilable
with various C++ compilers (although the situation is not perfect with
some of the compilers on some of the platforms tested.)

=head2 Ports

Perl has been reported to work on MidnightBSD.

=head1 Selected Bug Fixes

PerlIO::scalar will now prevent writing to read-only scalars. Moreover,
seek() is now supported with PerlIO::scalar-based filehandles, the
underlying string being zero-filled as needed.

study() never worked for UTF-8 strings, but could lead to false results.
It's now a no-op on UTF-8 data. (Yves Orton)

The signals SIGILL, SIGBUS and SIGSEGV are now always delivered in an
"unsafe" manner (contrary to other signals, that are deferred until the
perl interpreter reaches a reasonably stable state; see
L<perlipc/"Deferred Signals (Safe Signals)">).

=head1 New or Changed Diagnostics

=head1 Changed Internals

The anonymous hash and array constructors now take 1 op in the optree
instead of 3, now that pp_anonhash and pp_anonlist return a reference to
an hash/array when the op is flagged with OPf_SPECIAL (Nicholas Clark).

=head1 Known Problems

=head2 Platform Specific Problems

=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/rt3/ .  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.

=head1 SEE ALSO

The F<Changes> file for 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
f6eae373	1	=head1 NAME
	2
	3	perldelta - what is new for perl v5.9.5
	4
	5	=head1 DESCRIPTION
	6
	7	This document describes differences between the 5.9.4 and the 5.9.5
	8	development releases. See L<perl590delta>, L<perl591delta>,
	9	L<perl592delta>, L<perl593delta> and L<perl594delta> for the differences
	10	between 5.8.0 and 5.9.4.
	11
	12	=head1 Incompatible Changes
	13
20ee07fb	14	=head2 Tainting and printf
	15
	16	When perl is run under taint mode, C<printf()> and C<sprintf()> will now
	17	reject any tainted format argument.
	18
73966613	19	=head2 Removal of the bytecode compiler and of perlcc
	20
	21	C<perlcc>, the byteloader and the supporting modules (B::C, B::CC,
	22	B::Bytecode, etc.) are no longer distributed with the perl sources. Those
	23	experimental tools have never worked reliably, and, due to the lack of
	24	volunteers to keep them in line with the perl interpreter developments, it
	25	was decided to remove them instead of shipping a broken version of those.
	26	The last version of those modules can be found with perl 5.9.4.
	27
	28	However the B compiler framework stays supported in the perl core, as with
	29	the more useful modules it has permitted (among others, B::Deparse and
	30	B::Concise).
	31
	32	=head2 Removal of the JPL
	33
	34	The JPL (Java-Perl Linguo) has been removed from the perl sources tarball.
	35
f6eae373	36	=head1 Core Enhancements
f6eae373	37
072f65b4	38	=head2 Regular expressions
	39
	40	=over 4
	41
	42	=item Recursive Patterns
	43
	44	It is now possible to write recursive patterns without using the C<(??{})>
	45	construct. This new way is more efficient, and in many cases easier to
	46	read.
	47
	48	Each capturing parenthesis can now be treated as an independent pattern
	49	that can be entered by using the C<(?PARNO)> syntax (C<PARNO> standing for
	50	"parenthesis number"). For example, the following pattern will match
	51	nested balanced angle brackets:
	52
	53	/
	54	^ # start of line
	55	( # start capture buffer 1
	56	< # match an opening angle bracket
	57	(?: # match one of:
	58	(?> # don't backtrack over the inside of this group
	59	[^<>]+ # one or more non angle brackets
	60	) # end non backtracking group
	61	\| # ... or ...
	62	(?1) # recurse to bracket 1 and try it again
	63	)* # 0 or more times.
	64	> # match a closing angle bracket
	65	) # end capture buffer one
	66	$ # end of line
	67	/x
	68
	69	Note, users experienced with PCRE will find that the Perl implementation
	70	of this feature differs from the PCRE one in that it is possible to
	71	backtrack into a recursed pattern, whereas in PCRE the recursion is
73966613	72	atomic or "possessive" in nature. (Yves Orton)
072f65b4	73
	74	=item Named Capture Buffers
	75
	76	It is now possible to name capturing parenthesis in a pattern and refer to
	77	the captured contents by name. The naming syntax is C<< (?<NAME>....) >>.
	78	It's possible to backreference to a named buffer with the C<< \k<NAME> >>
	79	syntax. In code, the new magical hash C<%+> can be used to access the
	80	contents of the buffers.
	81
	82	Thus, to replace all doubled chars, one could write
	83
	84	s/(?<letter>.)\k<letter>/$+{letter}/g
	85
	86	Only buffers with defined contents will be "visible" in the hash, so
	87	it's possible to do something like
	88
	89	foreach my $name (keys %+) {
	90	print "content of buffer '$name' is $+{$name}\n";
	91	}
	92
	93	Users exposed to the .NET regex engine will find that the perl
	94	implementation differs in that the numerical ordering of the buffers
	95	is sequential, and not "unnamed first, then named". Thus in the pattern
	96
	97	/(A)(?<B>B)(C)(?<D>D)/
	98
	99	$1 will be 'A', $2 will be 'B', $3 will be 'C' and $4 will be 'D' and not
	100	$1 is 'A', $2 is 'C' and $3 is 'B' and $4 is 'D' that a .NET programmer
73966613	101	would expect. This is considered a feature. :-) (Yves Orton)
072f65b4	102
b9b4dddf	103	=item Possessive Quantifiers
	104
	105	Perl now supports the "possessive quantifier" syntax of the "atomic match"
	106	pattern. Basically a possessive quantifier matches as much as it can and never
	107	gives any back. Thus it can be used to control backtracking. The syntax is
	108	similar to non-greedy matching, except instead of using a '?' as the modifier
	109	the '+' is used. Thus C<?+>, C<*+>, C<++>, C<{min,max}+> are now legal
73966613	110	quantifiers. (Yves Orton)
b9b4dddf	111
24b23f37	112	=item Backtracking control verbs
	113
	114	The regex engine now supports a number of special purpose backtrack
e2e6a0f1	115	control verbs: (COMMIT), (MARK), (CUT), (ERROR), (*FAIL) and
e2e6a0f1	116	(*ACCEPT). See L<perlre> for their descriptions.
24b23f37	117
072f65b4	118	=back
072f65b4	119
d5494b07	120	=head2 The C<_> prototype
	121
	122	A new prototype character has been added. C<_> is equivalent to C<$> (it
	123	denotes a scalar), but defaults to C<$_> if the corresponding argument
	124	isn't supplied. Due to the optional nature of the argument, you can only
	125	use it at the end of a prototype, or before a semicolon.
	126
73966613	127	This has a small incompatible consequence: the prototype() function has
	128	been adjusted to return C<_> for some built-ins in appropriate cases (for
	129	example, C<prototype('CORE::rmdir')>). (Rafael Garcia-Suarez)
	130
49f595a6	131	=head2 UNITCHECK blocks
	132
	133	C<UNITCHECK>, a new special code block has been introduced, in addition to
	134	C<BEGIN>, C<CHECK>, C<INIT> and C<END>.
	135
	136	C<CHECK> and C<INIT> blocks, while useful for some specialized purposes,
	137	are always executed at the transition between the compilation and the
	138	execution of the main program, and thus are useless whenever code is
	139	loaded at runtime. On the other hand, C<UNITCHECK> blocks are executed
	140	just after the unit which defined them has been compiled. See L<perlmod>
	141	for more information. (Alex Gough)
	142
73966613	143	=head2 UCD 5.0.0
	144
	145	The copy of the Unicode Character Database included in Perl 5.9 has
	146	been updated to version 5.0.0.
	147
f6eae373	148	=head1 Modules and Pragmas
	149
	150	=head2 New Core Modules
	151
73966613	152	=over 4
	153
	154	=item *
	155
	156	C<Locale::Maketext::Simple>, needed by CPANPLUS, is a simple wrapper around
	157	C<Locale::Maketext::Lexicon>. Note that C<Locale::Maketext::Lexicon> isn't
	158	included in the perl core; the behaviour of C<Locale::Maketext::Simple>
	159	gracefully degrades when the later isn't present.
	160
	161	=item *
	162
	163	C<Params::Check> implements a generic input parsing/checking mechanism. It
	164	is used by CPANPLUS.
	165
	166	=back
	167
d5494b07	168	=head2 Module changes
	169
	170	=over 4
	171
	172	=item C<base>
	173
	174	The C<base> pragma now warns if a class tries to inherit from itself.
	175
18857c0b	176	=item C<warnings>
	177
	178	The C<warnings> pragma doesn't load C<Carp> anymore. That means that code
	179	that used C<Carp> routines without having loaded it at compile time might
	180	need to be adjusted; typically, the following (faulty) code won't work
	181	anymore, and will require parentheses to be added after the function name:
	182
	183	use warnings;
	184	require Carp;
	185	Carp::confess "argh";
	186
d5494b07	187	=back
d5494b07	188
f6eae373	189	=head1 Utility Changes
	190
	191	=head1 Documentation
	192
	193	=head1 Performance Enhancements
	194
	195	=head1 Installation and Configuration Improvements
	196
73966613	197	=head2 C++ compatibility
	198
	199	Efforts have been made to make perl and the core XS modules compilable
	200	with various C++ compilers (although the situation is not perfect with
	201	some of the compilers on some of the platforms tested.)
	202
	203	=head2 Ports
	204
	205	Perl has been reported to work on MidnightBSD.
	206
f6eae373	207	=head1 Selected Bug Fixes
f6eae373	208
49f595a6	209	PerlIO::scalar will now prevent writing to read-only scalars. Moreover,
	210	seek() is now supported with PerlIO::scalar-based filehandles, the
	211	underlying string being zero-filled as needed.
73966613	212
	213	study() never worked for UTF-8 strings, but could lead to false results.
	214	It's now a no-op on UTF-8 data. (Yves Orton)
	215
49f595a6	216	The signals SIGILL, SIGBUS and SIGSEGV are now always delivered in an
	217	"unsafe" manner (contrary to other signals, that are deferred until the
	218	perl interpreter reaches a reasonably stable state; see
	219	L<perlipc/"Deferred Signals (Safe Signals)">).
	220
f6eae373	221	=head1 New or Changed Diagnostics
	222
	223	=head1 Changed Internals
	224
73966613	225	The anonymous hash and array constructors now take 1 op in the optree
	226	instead of 3, now that pp_anonhash and pp_anonlist return a reference to
	227	an hash/array when the op is flagged with OPf_SPECIAL (Nicholas Clark).
	228
f6eae373	229	=head1 Known Problems
	230
	231	=head2 Platform Specific Problems
	232
	233	=head1 Reporting Bugs
	234
	235	If you find what you think is a bug, you might check the articles
	236	recently posted to the comp.lang.perl.misc newsgroup and the perl
	237	bug database at http://rt.perl.org/rt3/ . There may also be
	238	information at http://www.perl.org/ , the Perl Home Page.
	239
	240	If you believe you have an unreported bug, please run the B<perlbug>
	241	program included with your release. Be sure to trim your bug down
	242	to a tiny but sufficient test case. Your bug report, along with the
	243	output of C<perl -V>, will be sent off to perlbug@perl.org to be
	244	analysed by the Perl porting team.
	245
	246	=head1 SEE ALSO
	247
	248	The F<Changes> file for exhaustive details on what changed.
	249
	250	The F<INSTALL> file for how to build Perl.
	251
	252	The F<README> file for general stuff.
	253
	254	The F<Artistic> and F<Copying> files for copyright information.
	255
	256	=cut