| 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 | |
| 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. (Rafael Garcia-Suarez) |
| 18 | |
| 19 | =head2 undef and signal handlers |
| 20 | |
| 21 | Undefining or deleting a signal handler via C<undef $SIG{FOO}> is now |
| 22 | equivalent to setting it to C<'DEFAULT'>. (Rafael) |
| 23 | |
| 24 | =head2 strictures and array/hash dereferencing in defined() |
| 25 | |
| 26 | C<defined @$foo> and C<defined %$bar> are now subject to C<strict 'refs'> |
| 27 | (that is, C<$foo> and C<$bar> shall be proper references there.) |
| 28 | (Nicholas Clark) |
| 29 | |
| 30 | (However, C<defined(@foo)> and C<defined(%bar)> are discouraged constructs |
| 31 | anyway.) |
| 32 | |
| 33 | =head2 C<(?p{})> has been removed |
| 34 | |
| 35 | The regular expression construct C<(?p{})>, which was deprecated in perl |
| 36 | 5.8, has been removed. Use C<(??{})> instead. (Rafael) |
| 37 | |
| 38 | =head2 Removal of the bytecode compiler and of perlcc |
| 39 | |
| 40 | C<perlcc>, the byteloader and the supporting modules (B::C, B::CC, |
| 41 | B::Bytecode, etc.) are no longer distributed with the perl sources. Those |
| 42 | experimental tools have never worked reliably, and, due to the lack of |
| 43 | volunteers to keep them in line with the perl interpreter developments, it |
| 44 | was decided to remove them instead of shipping a broken version of those. |
| 45 | The last version of those modules can be found with perl 5.9.4. |
| 46 | |
| 47 | However the B compiler framework stays supported in the perl core, as with |
| 48 | the more useful modules it has permitted (among others, B::Deparse and |
| 49 | B::Concise). |
| 50 | |
| 51 | =head2 Removal of the JPL |
| 52 | |
| 53 | The JPL (Java-Perl Linguo) has been removed from the perl sources tarball. |
| 54 | |
| 55 | =head2 Recursive inheritance detected earlier |
| 56 | |
| 57 | Perl will now immediately throw an exception if you modify any package's |
| 58 | C<@ISA> in such a way that it would cause recursive inheritance. |
| 59 | |
| 60 | Previously, the exception would not occur until Perl attempted to make |
| 61 | use of the recursive inheritance while resolving a method or doing a |
| 62 | C<$foo-E<gt>isa($bar)> lookup. |
| 63 | |
| 64 | =head1 Core Enhancements |
| 65 | |
| 66 | =head2 Regular expressions |
| 67 | |
| 68 | =over 4 |
| 69 | |
| 70 | =item Recursive Patterns |
| 71 | |
| 72 | It is now possible to write recursive patterns without using the C<(??{})> |
| 73 | construct. This new way is more efficient, and in many cases easier to |
| 74 | read. |
| 75 | |
| 76 | Each capturing parenthesis can now be treated as an independent pattern |
| 77 | that can be entered by using the C<(?PARNO)> syntax (C<PARNO> standing for |
| 78 | "parenthesis number"). For example, the following pattern will match |
| 79 | nested balanced angle brackets: |
| 80 | |
| 81 | / |
| 82 | ^ # start of line |
| 83 | ( # start capture buffer 1 |
| 84 | < # match an opening angle bracket |
| 85 | (?: # match one of: |
| 86 | (?> # don't backtrack over the inside of this group |
| 87 | [^<>]+ # one or more non angle brackets |
| 88 | ) # end non backtracking group |
| 89 | | # ... or ... |
| 90 | (?1) # recurse to bracket 1 and try it again |
| 91 | )* # 0 or more times. |
| 92 | > # match a closing angle bracket |
| 93 | ) # end capture buffer one |
| 94 | $ # end of line |
| 95 | /x |
| 96 | |
| 97 | Note, users experienced with PCRE will find that the Perl implementation |
| 98 | of this feature differs from the PCRE one in that it is possible to |
| 99 | backtrack into a recursed pattern, whereas in PCRE the recursion is |
| 100 | atomic or "possessive" in nature. (Yves Orton) |
| 101 | |
| 102 | =item Named Capture Buffers |
| 103 | |
| 104 | It is now possible to name capturing parenthesis in a pattern and refer to |
| 105 | the captured contents by name. The naming syntax is C<< (?<NAME>....) >>. |
| 106 | It's possible to backreference to a named buffer with the C<< \k<NAME> >> |
| 107 | syntax. In code, the new magical hashes C<%+> and C<%-> can be used to |
| 108 | access the contents of the capture buffers. |
| 109 | |
| 110 | Thus, to replace all doubled chars, one could write |
| 111 | |
| 112 | s/(?<letter>.)\k<letter>/$+{letter}/g |
| 113 | |
| 114 | Only buffers with defined contents will be "visible" in the C<%+> hash, so |
| 115 | it's possible to do something like |
| 116 | |
| 117 | foreach my $name (keys %+) { |
| 118 | print "content of buffer '$name' is $+{$name}\n"; |
| 119 | } |
| 120 | |
| 121 | The C<%-> hash is a bit more complete, since it will contain array refs |
| 122 | holding values from all capture buffers similarly named, if there should |
| 123 | be many of them. |
| 124 | |
| 125 | C<%+> and C<%-> are implemented as tied hashes through the new module |
| 126 | C<Tie::Hash::NamedCapture>. |
| 127 | |
| 128 | Users exposed to the .NET regex engine will find that the perl |
| 129 | implementation differs in that the numerical ordering of the buffers |
| 130 | is sequential, and not "unnamed first, then named". Thus in the pattern |
| 131 | |
| 132 | /(A)(?<B>B)(C)(?<D>D)/ |
| 133 | |
| 134 | $1 will be 'A', $2 will be 'B', $3 will be 'C' and $4 will be 'D' and not |
| 135 | $1 is 'A', $2 is 'C' and $3 is 'B' and $4 is 'D' that a .NET programmer |
| 136 | would expect. This is considered a feature. :-) (Yves Orton) |
| 137 | |
| 138 | =item Possessive Quantifiers |
| 139 | |
| 140 | Perl now supports the "possessive quantifier" syntax of the "atomic match" |
| 141 | pattern. Basically a possessive quantifier matches as much as it can and never |
| 142 | gives any back. Thus it can be used to control backtracking. The syntax is |
| 143 | similar to non-greedy matching, except instead of using a '?' as the modifier |
| 144 | the '+' is used. Thus C<?+>, C<*+>, C<++>, C<{min,max}+> are now legal |
| 145 | quantifiers. (Yves Orton) |
| 146 | |
| 147 | =item Backtracking control verbs |
| 148 | |
| 149 | The regex engine now supports a number of special-purpose backtrack |
| 150 | control verbs: (*THEN), (*PRUNE), (*MARK), (*SKIP), (*COMMIT), (*FAIL) |
| 151 | and (*ACCEPT). See L<perlre> for their descriptions. (Yves Orton) |
| 152 | |
| 153 | =item Relative backreferences |
| 154 | |
| 155 | A new syntax C<\g{N}> or C<\gN> where "N" is a decimal integer allows a |
| 156 | safer form of back-reference notation as well as allowing relative |
| 157 | backreferences. This should make it easier to generate and embed patterns |
| 158 | that contain backreferences. See L<perlre/"Capture buffers">. (Yves Orton) |
| 159 | |
| 160 | =item C<\K> escape |
| 161 | |
| 162 | The functionality of Jeff Pinyan's module Regexp::Keep has been added to |
| 163 | the core. You can now use in regular expressions the special escape C<\K> |
| 164 | as a way to do something like floating length positive lookbehind. It is |
| 165 | also useful in substitutions like: |
| 166 | |
| 167 | s/(foo)bar/$1/g |
| 168 | |
| 169 | that can now be converted to |
| 170 | |
| 171 | s/foo\Kbar//g |
| 172 | |
| 173 | which is much more efficient. (Yves Orton) |
| 174 | |
| 175 | =item Vertical and horizontal whitespace, and linebreak |
| 176 | |
| 177 | Regular expressions now recognize the C<\v> and C<\h> escapes, that match |
| 178 | vertical and horizontal whitespace, respectively. C<\V> and C<\H> |
| 179 | logically match their complements. |
| 180 | |
| 181 | C<\R> matches a generic linebreak, that is, vertical whitespace, plus |
| 182 | the multi-character sequence C<"\x0D\x0A">. |
| 183 | |
| 184 | =back |
| 185 | |
| 186 | =head2 The C<_> prototype |
| 187 | |
| 188 | A new prototype character has been added. C<_> is equivalent to C<$> (it |
| 189 | denotes a scalar), but defaults to C<$_> if the corresponding argument |
| 190 | isn't supplied. Due to the optional nature of the argument, you can only |
| 191 | use it at the end of a prototype, or before a semicolon. |
| 192 | |
| 193 | This has a small incompatible consequence: the prototype() function has |
| 194 | been adjusted to return C<_> for some built-ins in appropriate cases (for |
| 195 | example, C<prototype('CORE::rmdir')>). (Rafael) |
| 196 | |
| 197 | =head2 UNITCHECK blocks |
| 198 | |
| 199 | C<UNITCHECK>, a new special code block has been introduced, in addition to |
| 200 | C<BEGIN>, C<CHECK>, C<INIT> and C<END>. |
| 201 | |
| 202 | C<CHECK> and C<INIT> blocks, while useful for some specialized purposes, |
| 203 | are always executed at the transition between the compilation and the |
| 204 | execution of the main program, and thus are useless whenever code is |
| 205 | loaded at runtime. On the other hand, C<UNITCHECK> blocks are executed |
| 206 | just after the unit which defined them has been compiled. See L<perlmod> |
| 207 | for more information. (Alex Gough) |
| 208 | |
| 209 | =head2 readpipe() is now overridable |
| 210 | |
| 211 | The built-in function readpipe() is now overridable. Overriding it permits |
| 212 | also to override its operator counterpart, C<qx//> (a.k.a. C<``>). |
| 213 | Moreover, it now defaults to C<$_> if no argument is provided. (Rafael) |
| 214 | |
| 215 | =head2 default argument for readline() |
| 216 | |
| 217 | readline() now defaults to C<*ARGV> if no argument is provided. (Rafael) |
| 218 | |
| 219 | =head2 UCD 5.0.0 |
| 220 | |
| 221 | The copy of the Unicode Character Database included in Perl 5.9 has |
| 222 | been updated to version 5.0.0. |
| 223 | |
| 224 | =head2 Smart match |
| 225 | |
| 226 | The smart match operator (C<~~>) is now available by default (you don't |
| 227 | need to enable it with C<use feature> any longer). (Michael G Schwern) |
| 228 | |
| 229 | =head2 Implicit loading of C<feature> |
| 230 | |
| 231 | The C<feature> pragma is now implicitly loaded when you require a minimal |
| 232 | perl version (with the C<use VERSION> construct) greater than, or equal |
| 233 | to, 5.9.5. |
| 234 | |
| 235 | =head1 Modules and Pragmas |
| 236 | |
| 237 | =head2 New Pragma, C<mro> |
| 238 | |
| 239 | A new pragma, C<mro> (for Method Resolution Order) has been added. It |
| 240 | permits to switch, on a per-class basis, the algorithm that perl uses to |
| 241 | find inherited methods in case of a mutiple inheritance hierachy. The |
| 242 | default MRO hasn't changed (DFS, for Depth First Search). Another MRO is |
| 243 | available: the C3 algorithm. See L<mro> for more information. |
| 244 | (Brandon Black) |
| 245 | |
| 246 | =head2 bignum, bigint, bigrat |
| 247 | |
| 248 | The three numeric pragmas C<bignum>, C<bigint> and C<bigrat> are now |
| 249 | lexically scoped. (Tels) |
| 250 | |
| 251 | =head2 New Core Modules |
| 252 | |
| 253 | =over 4 |
| 254 | |
| 255 | =item * |
| 256 | |
| 257 | C<Locale::Maketext::Simple>, needed by CPANPLUS, is a simple wrapper around |
| 258 | C<Locale::Maketext::Lexicon>. Note that C<Locale::Maketext::Lexicon> isn't |
| 259 | included in the perl core; the behaviour of C<Locale::Maketext::Simple> |
| 260 | gracefully degrades when the later isn't present. |
| 261 | |
| 262 | =item * |
| 263 | |
| 264 | C<Params::Check> implements a generic input parsing/checking mechanism. It |
| 265 | is used by CPANPLUS. |
| 266 | |
| 267 | =item * |
| 268 | |
| 269 | C<Term::UI> simplifies the task to ask questions at a terminal prompt. |
| 270 | |
| 271 | =item * |
| 272 | |
| 273 | C<Object::Accessor> provides an interface to create per-object accessors. |
| 274 | |
| 275 | =item * |
| 276 | |
| 277 | C<Module::Pluggable> is a simple framework to create modules that accept |
| 278 | pluggable sub-modules. |
| 279 | |
| 280 | =item * |
| 281 | |
| 282 | C<Module::Load::Conditional> provides simple ways to query and possibly |
| 283 | load installed modules. |
| 284 | |
| 285 | =item * |
| 286 | |
| 287 | C<Time::Piece> provides an object oriented interface to time functions, |
| 288 | overriding the built-ins localtime() and gmtime(). |
| 289 | |
| 290 | =item * |
| 291 | |
| 292 | C<IPC::Cmd> helps to find and run external commands, possibly |
| 293 | interactively. |
| 294 | |
| 295 | =item * |
| 296 | |
| 297 | C<File::Fetch> provide a simple generic file fetching mechanism. |
| 298 | |
| 299 | =item * |
| 300 | |
| 301 | C<Archive::Extract> is a generic archive extraction mechanism |
| 302 | for F<.tar> (plain, gziped or bzipped) or F<.zip> files. |
| 303 | |
| 304 | =item * |
| 305 | |
| 306 | C<CPANPLUS> provides an API and a command-line tool to access the CPAN |
| 307 | mirrors. |
| 308 | |
| 309 | =back |
| 310 | |
| 311 | =head2 Module changes |
| 312 | |
| 313 | =over 4 |
| 314 | |
| 315 | =item C<assertions> |
| 316 | |
| 317 | The C<assertions> pragma, its submodules C<assertions::activate> and |
| 318 | C<assertions::compat> and the B<-A> command-line switch have been removed. |
| 319 | The interface was not judged mature enough for inclusion in a stable |
| 320 | release. |
| 321 | |
| 322 | =item C<base> |
| 323 | |
| 324 | The C<base> pragma now warns if a class tries to inherit from itself. |
| 325 | (Curtis "Ovid" Poe) |
| 326 | |
| 327 | =item C<strict> and C<warnings> |
| 328 | |
| 329 | C<strict> and C<warnings> will now complain loudly if they are loaded via |
| 330 | incorrect casing (as in C<use Strict;>). (Johan Vromans) |
| 331 | |
| 332 | =item C<warnings> |
| 333 | |
| 334 | The C<warnings> pragma doesn't load C<Carp> anymore. That means that code |
| 335 | that used C<Carp> routines without having loaded it at compile time might |
| 336 | need to be adjusted; typically, the following (faulty) code won't work |
| 337 | anymore, and will require parentheses to be added after the function name: |
| 338 | |
| 339 | use warnings; |
| 340 | require Carp; |
| 341 | Carp::confess "argh"; |
| 342 | |
| 343 | =item C<less> |
| 344 | |
| 345 | C<less> now does something useful (or at least it tries to). In fact, it |
| 346 | has been turned into a lexical pragma. So, in your modules, you can now |
| 347 | test whether your users have requested to use less CPU, or less memory, |
| 348 | less magic, or maybe even less fat. See L<less> for more. (Joshua ben |
| 349 | Jore) |
| 350 | |
| 351 | =item C<Attribute::Handlers> |
| 352 | |
| 353 | C<Attribute::Handlers> can now report the caller's file and line number. |
| 354 | (David Feldman) |
| 355 | |
| 356 | =item C<B::Lint> |
| 357 | |
| 358 | C<B::Lint> is now based on C<Module::Pluggable>, and so can be extended |
| 359 | with plugins. (Joshua ben Jore) |
| 360 | |
| 361 | =item C<B> |
| 362 | |
| 363 | It's now possible to access the lexical pragma hints (C<%^H>) by using the |
| 364 | method B::COP::hints_hash(). It returns a C<B::RHE> object, which in turn |
| 365 | can be used to get a hash reference via the method B::RHE::HASH(). (Joshua |
| 366 | ben Jore) |
| 367 | |
| 368 | =for p5p XXX document this in B.pm too |
| 369 | |
| 370 | =item C<Thread> |
| 371 | |
| 372 | As the old 5005thread threading model has been removed, in favor of the |
| 373 | ithreads scheme, the C<Thread> module is now a compatibility wrapper, to |
| 374 | be used in old code only. |
| 375 | |
| 376 | =back |
| 377 | |
| 378 | =head1 Utility Changes |
| 379 | |
| 380 | =head2 C<cpanp> |
| 381 | |
| 382 | C<cpanp>, the CPANPLUS shell, has been added. (C<cpanp-run-perl>, an |
| 383 | helper for CPANPLUS operation, has been added too, but isn't intended for |
| 384 | direct use). |
| 385 | |
| 386 | =head2 C<cpan2dist> |
| 387 | |
| 388 | C<cpan2dist> is a new utility, that comes with CPANPLUS. It's a tool to |
| 389 | create distributions (or packages) from CPAN modules. |
| 390 | |
| 391 | =head2 C<pod2html> |
| 392 | |
| 393 | The output of C<pod2html> has been enhanced to be more customizable via |
| 394 | CSS. Some formatting problems were also corrected. (Jari Aalto) |
| 395 | |
| 396 | =head1 Documentation |
| 397 | |
| 398 | =head2 New manpage, perlunifaq |
| 399 | |
| 400 | A new manual page, L<perlunifaq> (the Perl Unicode FAQ), has been added |
| 401 | (Juerd Waalboer). |
| 402 | |
| 403 | =head1 Performance Enhancements |
| 404 | |
| 405 | =head1 Installation and Configuration Improvements |
| 406 | |
| 407 | =head2 C++ compatibility |
| 408 | |
| 409 | Efforts have been made to make perl and the core XS modules compilable |
| 410 | with various C++ compilers (although the situation is not perfect with |
| 411 | some of the compilers on some of the platforms tested.) |
| 412 | |
| 413 | =head2 Visual C++ |
| 414 | |
| 415 | Perl now can be compiled with Microsoft Visual C++ 2005. |
| 416 | |
| 417 | =head2 Static build on Win32 |
| 418 | |
| 419 | It's now possible to build a C<perl-static.exe> that doesn't depend |
| 420 | on C<perl59.dll> on Win32. See the Win32 makefiles for details. |
| 421 | (Vadim Konovalov) |
| 422 | |
| 423 | =head2 C<d_pseudofork> |
| 424 | |
| 425 | A new configuration variable, available as C<$Config{d_pseudofork}> in |
| 426 | the L<Config> module, has been added, to distinguish real fork() support |
| 427 | from fake pseudofork used on Windows platforms. |
| 428 | |
| 429 | =head2 Ports |
| 430 | |
| 431 | Perl has been reported to work on MidnightBSD. |
| 432 | |
| 433 | =head1 Selected Bug Fixes |
| 434 | |
| 435 | PerlIO::scalar will now prevent writing to read-only scalars. Moreover, |
| 436 | seek() is now supported with PerlIO::scalar-based filehandles, the |
| 437 | underlying string being zero-filled as needed. (Rafael, Jarkko Hietaniemi) |
| 438 | |
| 439 | study() never worked for UTF-8 strings, but could lead to false results. |
| 440 | It's now a no-op on UTF-8 data. (Yves Orton) |
| 441 | |
| 442 | The signals SIGILL, SIGBUS and SIGSEGV are now always delivered in an |
| 443 | "unsafe" manner (contrary to other signals, that are deferred until the |
| 444 | perl interpreter reaches a reasonably stable state; see |
| 445 | L<perlipc/"Deferred Signals (Safe Signals)">). (Rafael) |
| 446 | |
| 447 | When a module or a file is loaded through an @INC-hook, and when this hook |
| 448 | has set a filename entry in %INC, __FILE__ is now set for this module |
| 449 | accordingly to the contents of that %INC entry. (Rafael) |
| 450 | |
| 451 | The C<-w> and C<-t> switches can now be used together without messing |
| 452 | up what categories of warnings are activated or not. (Rafael) |
| 453 | |
| 454 | Duping a filehandle which has the C<:utf8> PerlIO layer set will now |
| 455 | properly carry that layer on the duped filehandle. (Rafael) |
| 456 | |
| 457 | Localizing an hash element whose key was given as a variable didn't work |
| 458 | correctly if the variable was changed while the local() was in effect (as |
| 459 | in C<local $h{$x}; ++$x>). (Bo Lindbergh) |
| 460 | |
| 461 | =head1 New or Changed Diagnostics |
| 462 | |
| 463 | =head2 Deprecations |
| 464 | |
| 465 | Two deprecation warnings have been added: (Rafael) |
| 466 | |
| 467 | Opening dirhandle %s also as a file |
| 468 | Opening filehandle %s also as a directory |
| 469 | |
| 470 | =head1 Changed Internals |
| 471 | |
| 472 | The anonymous hash and array constructors now take 1 op in the optree |
| 473 | instead of 3, now that pp_anonhash and pp_anonlist return a reference to |
| 474 | an hash/array when the op is flagged with OPf_SPECIAL (Nicholas Clark). |
| 475 | |
| 476 | =for p5p XXX have we some docs on how to create regexp engine plugins, since that's now possible ? (perlreguts) |
| 477 | |
| 478 | =for p5p XXX new BIND SV type, #29544, #29642 |
| 479 | |
| 480 | =head1 Known Problems |
| 481 | |
| 482 | =head2 Platform Specific Problems |
| 483 | |
| 484 | =head1 Reporting Bugs |
| 485 | |
| 486 | If you find what you think is a bug, you might check the articles |
| 487 | recently posted to the comp.lang.perl.misc newsgroup and the perl |
| 488 | bug database at http://rt.perl.org/rt3/ . There may also be |
| 489 | information at http://www.perl.org/ , the Perl Home Page. |
| 490 | |
| 491 | If you believe you have an unreported bug, please run the B<perlbug> |
| 492 | program included with your release. Be sure to trim your bug down |
| 493 | to a tiny but sufficient test case. Your bug report, along with the |
| 494 | output of C<perl -V>, will be sent off to perlbug@perl.org to be |
| 495 | analysed by the Perl porting team. |
| 496 | |
| 497 | =head1 SEE ALSO |
| 498 | |
| 499 | The F<Changes> file for exhaustive details on what changed. |
| 500 | |
| 501 | The F<INSTALL> file for how to build Perl. |
| 502 | |
| 503 | The F<README> file for general stuff. |
| 504 | |
| 505 | The F<Artistic> and F<Copying> files for copyright information. |
| 506 | |
| 507 | =cut |