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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 | |
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14 | =head2 Tainting and printf |
15 | |
16 | When perl is run under taint mode, C<printf()> and C<sprintf()> will now |
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17 | reject any tainted format argument. (Rafael Garcia-Suarez) |
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18 | |
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19 | =head2 undef and signal handlers |
20 | |
21 | Undefining or deleting a signal handler via C<undef $SIG{FOO}> is now |
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22 | equivalent to setting it to C<'DEFAULT'>. (Rafael) |
23 | |
24 | =head2 strictures and array/hash dereferencing in defined() |
25 | |
26 | C<defined @$foo> and C<defined %$bar> are now subject to C<strict 'refs'> |
27 | (that is, C<$foo> and C<$bar> shall be proper references there.) |
28 | (Nicholas Clark) |
29 | |
30 | (However, C<defined(@foo)> and C<defined(%bar)> are discouraged constructs |
31 | anyway.) |
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32 | |
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33 | =head2 Removal of the bytecode compiler and of perlcc |
34 | |
35 | C<perlcc>, the byteloader and the supporting modules (B::C, B::CC, |
36 | B::Bytecode, etc.) are no longer distributed with the perl sources. Those |
37 | experimental tools have never worked reliably, and, due to the lack of |
38 | volunteers to keep them in line with the perl interpreter developments, it |
39 | was decided to remove them instead of shipping a broken version of those. |
40 | The last version of those modules can be found with perl 5.9.4. |
41 | |
42 | However the B compiler framework stays supported in the perl core, as with |
43 | the more useful modules it has permitted (among others, B::Deparse and |
44 | B::Concise). |
45 | |
46 | =head2 Removal of the JPL |
47 | |
48 | The JPL (Java-Perl Linguo) has been removed from the perl sources tarball. |
49 | |
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50 | =head1 Core Enhancements |
51 | |
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52 | =head2 Regular expressions |
53 | |
54 | =over 4 |
55 | |
56 | =item Recursive Patterns |
57 | |
58 | It is now possible to write recursive patterns without using the C<(??{})> |
59 | construct. This new way is more efficient, and in many cases easier to |
60 | read. |
61 | |
62 | Each capturing parenthesis can now be treated as an independent pattern |
63 | that can be entered by using the C<(?PARNO)> syntax (C<PARNO> standing for |
64 | "parenthesis number"). For example, the following pattern will match |
65 | nested balanced angle brackets: |
66 | |
67 | / |
68 | ^ # start of line |
69 | ( # start capture buffer 1 |
70 | < # match an opening angle bracket |
71 | (?: # match one of: |
72 | (?> # don't backtrack over the inside of this group |
73 | [^<>]+ # one or more non angle brackets |
74 | ) # end non backtracking group |
75 | | # ... or ... |
76 | (?1) # recurse to bracket 1 and try it again |
77 | )* # 0 or more times. |
78 | > # match a closing angle bracket |
79 | ) # end capture buffer one |
80 | $ # end of line |
81 | /x |
82 | |
83 | Note, users experienced with PCRE will find that the Perl implementation |
84 | of this feature differs from the PCRE one in that it is possible to |
85 | backtrack into a recursed pattern, whereas in PCRE the recursion is |
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86 | atomic or "possessive" in nature. (Yves Orton) |
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87 | |
88 | =item Named Capture Buffers |
89 | |
90 | It is now possible to name capturing parenthesis in a pattern and refer to |
91 | the captured contents by name. The naming syntax is C<< (?<NAME>....) >>. |
92 | It's possible to backreference to a named buffer with the C<< \k<NAME> >> |
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93 | syntax. In code, the new magical hashes C<%+> and C<%-> can be used to |
94 | access the contents of the capture buffers. |
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95 | |
96 | Thus, to replace all doubled chars, one could write |
97 | |
98 | s/(?<letter>.)\k<letter>/$+{letter}/g |
99 | |
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100 | Only buffers with defined contents will be "visible" in the C<%+> hash, so |
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101 | it's possible to do something like |
102 | |
103 | foreach my $name (keys %+) { |
104 | print "content of buffer '$name' is $+{$name}\n"; |
105 | } |
106 | |
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107 | The C<%-> hash is a bit more complete, since it will contain array refs |
108 | holding values from all capture buffers similarly named, if there should |
109 | be many of them. |
110 | |
111 | C<%+> and C<%-> are implemented as tied hashes through the new module |
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112 | C<Tie::Hash::NamedCapture>. |
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113 | |
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114 | Users exposed to the .NET regex engine will find that the perl |
115 | implementation differs in that the numerical ordering of the buffers |
116 | is sequential, and not "unnamed first, then named". Thus in the pattern |
117 | |
118 | /(A)(?<B>B)(C)(?<D>D)/ |
119 | |
120 | $1 will be 'A', $2 will be 'B', $3 will be 'C' and $4 will be 'D' and not |
121 | $1 is 'A', $2 is 'C' and $3 is 'B' and $4 is 'D' that a .NET programmer |
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122 | would expect. This is considered a feature. :-) (Yves Orton) |
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123 | |
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124 | =item Possessive Quantifiers |
125 | |
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126 | Perl now supports the "possessive quantifier" syntax of the "atomic match" |
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127 | pattern. Basically a possessive quantifier matches as much as it can and never |
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128 | gives any back. Thus it can be used to control backtracking. The syntax is |
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129 | similar to non-greedy matching, except instead of using a '?' as the modifier |
130 | the '+' is used. Thus C<?+>, C<*+>, C<++>, C<{min,max}+> are now legal |
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131 | quantifiers. (Yves Orton) |
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132 | |
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133 | =item Backtracking control verbs |
134 | |
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135 | The regex engine now supports a number of special-purpose backtrack |
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136 | control verbs: (*THEN), (*PRUNE), (*MARK), (*SKIP), (*COMMIT), (*FAIL) |
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137 | and (*ACCEPT). See L<perlre> for their descriptions. (Yves Orton) |
138 | |
139 | =item Relative backreferences |
140 | |
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141 | A new syntax C<\g{N}> or C<\gN> where "N" is a decimal integer allows a |
142 | safer form of back-reference notation as well as allowing relative |
143 | backreferences. This should make it easier to generate and embed patterns |
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144 | that contain backreferences. See L<perlre/"Capture buffers">. (Yves Orton) |
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145 | |
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146 | =item C<\K> escape |
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147 | |
148 | The functionality of Jeff Pinyan's module Regexp::Keep has been added to |
149 | the core. You can now use in regular expressions the special escape C<\K> |
150 | as a way to do something like floating length positive lookbehind. It is |
151 | also useful in substitutions like: |
152 | |
153 | s/(foo)bar/$1/g |
154 | |
155 | that can now be converted to |
156 | |
157 | s/foo\Kbar//g |
158 | |
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159 | which is much more efficient. (Yves Orton) |
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160 | |
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161 | =back |
162 | |
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163 | =head2 The C<_> prototype |
164 | |
165 | A new prototype character has been added. C<_> is equivalent to C<$> (it |
166 | denotes a scalar), but defaults to C<$_> if the corresponding argument |
167 | isn't supplied. Due to the optional nature of the argument, you can only |
168 | use it at the end of a prototype, or before a semicolon. |
169 | |
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170 | This has a small incompatible consequence: the prototype() function has |
171 | been adjusted to return C<_> for some built-ins in appropriate cases (for |
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172 | example, C<prototype('CORE::rmdir')>). (Rafael) |
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173 | |
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174 | =head2 UNITCHECK blocks |
175 | |
176 | C<UNITCHECK>, a new special code block has been introduced, in addition to |
177 | C<BEGIN>, C<CHECK>, C<INIT> and C<END>. |
178 | |
179 | C<CHECK> and C<INIT> blocks, while useful for some specialized purposes, |
180 | are always executed at the transition between the compilation and the |
181 | execution of the main program, and thus are useless whenever code is |
182 | loaded at runtime. On the other hand, C<UNITCHECK> blocks are executed |
183 | just after the unit which defined them has been compiled. See L<perlmod> |
184 | for more information. (Alex Gough) |
185 | |
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186 | =head2 readpipe() is now overridable |
187 | |
188 | The built-in function readpipe() is now overridable. Overriding it permits |
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189 | also to override its operator counterpart, C<qx//> (a.k.a. C<``>). (Rafael) |
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190 | |
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191 | =head2 UCD 5.0.0 |
192 | |
193 | The copy of the Unicode Character Database included in Perl 5.9 has |
194 | been updated to version 5.0.0. |
195 | |
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196 | =head2 Smart match |
197 | |
198 | The smart match operator (C<~~>) is now available by default (you don't |
199 | need to enable it with C<use feature> any longer). (Michael G Schwern) |
200 | |
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201 | =head1 Modules and Pragmas |
202 | |
203 | =head2 New Core Modules |
204 | |
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205 | =over 4 |
206 | |
207 | =item * |
208 | |
209 | C<Locale::Maketext::Simple>, needed by CPANPLUS, is a simple wrapper around |
210 | C<Locale::Maketext::Lexicon>. Note that C<Locale::Maketext::Lexicon> isn't |
211 | included in the perl core; the behaviour of C<Locale::Maketext::Simple> |
212 | gracefully degrades when the later isn't present. |
213 | |
214 | =item * |
215 | |
216 | C<Params::Check> implements a generic input parsing/checking mechanism. It |
217 | is used by CPANPLUS. |
218 | |
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219 | =item * |
220 | |
221 | C<Term::UI> simplifies the task to ask questions at a terminal prompt. |
222 | |
223 | =item * |
224 | |
225 | C<Object::Accessor> provides an interface to create per-object accessors. |
226 | |
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227 | =item * |
228 | |
229 | C<Module::Pluggable> is a simple framework to create modules that accept |
230 | pluggable sub-modules. |
231 | |
232 | =item * |
233 | |
234 | C<Module::Load::Conditional> provides simple ways to query and possibly |
235 | load installed modules. |
236 | |
237 | =item * |
238 | |
239 | C<Time::Piece> provides an object oriented interface to time functions, |
240 | overriding the built-ins localtime() and gmtime(). |
241 | |
242 | =item * |
243 | |
244 | C<IPC::Cmd> helps to find and run external commands, possibly |
245 | interactively. |
246 | |
247 | =item * |
248 | |
249 | C<File::Fetch> provide a simple generic file fetching mechanism. |
250 | |
251 | =item * |
252 | |
253 | C<Archive::Extract> is a generic archive extraction mechanism |
254 | for F<.tar> (plain, gziped or bzipped) or F<.zip> files. |
255 | |
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256 | =back |
257 | |
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258 | =head2 Module changes |
259 | |
260 | =over 4 |
261 | |
262 | =item C<base> |
263 | |
264 | The C<base> pragma now warns if a class tries to inherit from itself. |
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265 | (Curtis "Ovid" Poe) |
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266 | |
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267 | =item C<warnings> |
268 | |
269 | The C<warnings> pragma doesn't load C<Carp> anymore. That means that code |
270 | that used C<Carp> routines without having loaded it at compile time might |
271 | need to be adjusted; typically, the following (faulty) code won't work |
272 | anymore, and will require parentheses to be added after the function name: |
273 | |
274 | use warnings; |
275 | require Carp; |
276 | Carp::confess "argh"; |
277 | |
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278 | =item C<less> |
279 | |
280 | C<less> now does something useful (or at least it tries to). In fact, it |
281 | has been turned into a lexical pragma. So, in your modules, you can now |
282 | test whether your users have requested to use less CPU, or less memory, |
283 | less magic, or maybe even less fat. See L<less> for more. (Joshua ben |
284 | Jore) |
285 | |
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286 | =item C<Attribute::Handlers> |
287 | |
288 | C<Attribute::Handlers> can now report the caller's file and line number. |
289 | (David Feldman) |
290 | |
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291 | =item C<B::Lint> |
292 | |
293 | C<B::Lint> is now based on C<Module::Pluggable>, and so can be extended |
294 | with plugins. (Joshua ben Jore) |
295 | |
296 | =item C<B> |
297 | |
298 | It's now possible to access the lexical pragma hints (C<%^H>) by using the |
299 | method B::COP::hints_hash(). It returns a C<B::RHE> object, which in turn |
300 | can be used to get a hash reference via the method B::RHE::HASH(). (Joshua |
301 | ben Jore) |
302 | |
303 | =for p5p XXX document this in B.pm too |
304 | |
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305 | =back |
306 | |
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307 | =head1 Utility Changes |
308 | |
309 | =head1 Documentation |
310 | |
311 | =head1 Performance Enhancements |
312 | |
313 | =head1 Installation and Configuration Improvements |
314 | |
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315 | =head2 C++ compatibility |
316 | |
317 | Efforts have been made to make perl and the core XS modules compilable |
318 | with various C++ compilers (although the situation is not perfect with |
319 | some of the compilers on some of the platforms tested.) |
320 | |
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321 | =head2 Static build on Win32 |
322 | |
323 | It's now possible to build a C<perl-static.exe> that doesn't depend |
324 | on C<perl59.dll> on Win32. See the Win32 makefiles for details. |
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325 | (Vadim Konovalov) |
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326 | |
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327 | =head2 Ports |
328 | |
329 | Perl has been reported to work on MidnightBSD. |
330 | |
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331 | =head1 Selected Bug Fixes |
332 | |
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333 | PerlIO::scalar will now prevent writing to read-only scalars. Moreover, |
334 | seek() is now supported with PerlIO::scalar-based filehandles, the |
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335 | underlying string being zero-filled as needed. (Rafael, Jarkko Hietaniemi) |
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336 | |
337 | study() never worked for UTF-8 strings, but could lead to false results. |
338 | It's now a no-op on UTF-8 data. (Yves Orton) |
339 | |
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340 | The signals SIGILL, SIGBUS and SIGSEGV are now always delivered in an |
341 | "unsafe" manner (contrary to other signals, that are deferred until the |
342 | perl interpreter reaches a reasonably stable state; see |
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343 | L<perlipc/"Deferred Signals (Safe Signals)">). (Rafael) |
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344 | |
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345 | When a module or a file is loaded through an @INC-hook, and when this hook |
346 | has set a filename entry in %INC, __FILE__ is now set for this module |
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347 | accordingly to the contents of that %INC entry. (Rafael) |
348 | |
349 | The C<-w> and C<-t> switches can now be used together without messing |
350 | up what categories of warnings are activated or not. (Rafael) |
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351 | |
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352 | =head1 New or Changed Diagnostics |
353 | |
354 | =head1 Changed Internals |
355 | |
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356 | The anonymous hash and array constructors now take 1 op in the optree |
357 | instead of 3, now that pp_anonhash and pp_anonlist return a reference to |
358 | an hash/array when the op is flagged with OPf_SPECIAL (Nicholas Clark). |
359 | |
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360 | =for p5p XXX have we some docs on how to create regexp engine plugins, since that's now possible ? (perlreguts) |
361 | |
362 | =for p5p XXX new BIND SV type, #29544, #29642 |
363 | |
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364 | =head1 Known Problems |
365 | |
366 | =head2 Platform Specific Problems |
367 | |
368 | =head1 Reporting Bugs |
369 | |
370 | If you find what you think is a bug, you might check the articles |
371 | recently posted to the comp.lang.perl.misc newsgroup and the perl |
372 | bug database at http://rt.perl.org/rt3/ . There may also be |
373 | information at http://www.perl.org/ , the Perl Home Page. |
374 | |
375 | If you believe you have an unreported bug, please run the B<perlbug> |
376 | program included with your release. Be sure to trim your bug down |
377 | to a tiny but sufficient test case. Your bug report, along with the |
378 | output of C<perl -V>, will be sent off to perlbug@perl.org to be |
379 | analysed by the Perl porting team. |
380 | |
381 | =head1 SEE ALSO |
382 | |
383 | The F<Changes> file for exhaustive details on what changed. |
384 | |
385 | The F<INSTALL> file for how to build Perl. |
386 | |
387 | The F<README> file for general stuff. |
388 | |
389 | The F<Artistic> and F<Copying> files for copyright information. |
390 | |
391 | =cut |