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1 =head1 NAME 2 3 perl593delta - what is new for perl v5.9.3 4 5 =head1 DESCRIPTION 6 7 This document describes differences between the 5.9.2 and the 5.9.3 8 development releases. See L<perl590delta>, L<perl591delta> and 9 L<perl592delta> for the differences between 5.8.0 and 5.9.2. 10 11 =head1 Incompatible Changes 12 13 =head2 Parsing of C<-f _> 14 15 The identifier C<_> is now forced to be a bareword after a filetest 16 operator. This solves a number of misparsing issues when a global C<_> 17 subroutine is defined. 18 19 =head2 C<mkdir()> 20 21 C<mkdir()> without arguments now defaults to C<$_>. 22 23 =head2 Magic goto and eval 24 25 The construct C<eval { goto &foo }> is now disallowed. (Note that the 26 similar construct, but with C<eval("")> instead, was already forbidden.) 27 28 =head2 C<$#> has been removed 29 30 The deprecated C<$#> variable (output format for numbers) has been 31 removed. A new warning, C<$# is no longer supported>, has been added. 32 33 =head2 C<:unique> 34 35 The C<:unique> attribute has been made a no-op, since its current 36 implementation was fundamentally flawed and not threadsafe. 37 38 =head2 Scoping of the C<sort> pragma 39 40 The C<sort> pragma is now lexically scoped. Its effect used to be global. 41 42 =head1 Core Enhancements 43 44 =head2 The C<feature> pragma 45 46 The C<feature> pragma is used to enable new syntax that would break Perl's 47 backwards-compatibility with older releases of the language. It's a lexical 48 pragma, like C<strict> or C<warnings>. 49 50 Currently the following new features are available: C<switch> (adds a 51 switch statement), C<~~> (adds a Perl 6-like smart match operator), C<say> 52 (adds a C<say> built-in function), and C<err> (adds an C<err> keyword). 53 Those features are described below. 54 55 Note that C<err> low-precedence defined-or operator used to be enabled by 56 default (although as a weak keyword, meaning that any function would 57 override it). It's now only recognized when explicitly turned on (and is 58 then a regular keyword). 59 60 Those features, and the C<feature> pragma itself, have been contributed by 61 Robin Houston. 62 63 =head2 Switch and Smart Match operator 64 65 Perl 5 now has a switch statement. It's available when C<use feature 66 'switch'> is in effect. This feature introduces three new keywords, 67 C<given>, C<when>, and C<default>: 68 69 given ($foo) { 70 when (/^abc/) { $abc = 1; } 71 when (/^def/) { $def = 1; } 72 when (/^xyz/) { $xyz = 1; } 73 default { $nothing = 1; } 74 } 75 76 A more complete description of how Perl matches the switch variable 77 against the C<when> conditions is given in L<perlsyn/"Switch statements">. 78 79 This kind of match is called I<smart match>, and it's also possible to use 80 it outside of switch statements, via the new C<~~> operator (enabled via 81 the C<use feature '~~'> directive). See L<perlsyn/"Smart matching in 82 detail">. 83 84 =head2 C<say()> 85 86 say() is a new built-in, only available when C<use feature 'say'> is in 87 effect, that is similar to print(), but that implicitly appends a newline 88 to the printed string. See L<perlfunc/say>. 89 90 =head2 C<CLONE_SKIP()> 91 92 Perl has now support for the C<CLONE_SKIP> special subroutine. Like 93 C<CLONE>, C<CLONE_SKIP> is called once per package; however, it is called 94 just before cloning starts, and in the context of the parent thread. If it 95 returns a true value, then no objects of that class will be cloned. See 96 L<perlmod> for details. (Contributed by Dave Mitchell.) 97 98 =head2 C<${^CHILD_ERROR_NATIVE}> 99 100 A new internal variable, C<${^CHILD_ERROR_NATIVE}>, gives the native 101 status returned by the last pipe close, backtick command, successful call 102 to wait() or waitpid(), or from the system() operator. See L<perlrun> for 103 details. (Contributed by Gisle Aas.) 104 105 =head2 Assertions 106 107 The support for assertions, introduced in perl 5.9.0, has been improved. 108 The syntax for the C<-A> command-line switch has changed; it now accepts 109 an optional module name, defaulting to C<assertions::activate>. See 110 L<assertions> and L<perlrun>. (Contributed by Salvador Fandiño García.) 111 112 =head2 Unicode Character Database 4.1.0 113 114 The copy of the Unicode Character Database included in Perl 5.9 has 115 been updated to 4.1.0. 116 117 =head2 C<no VERSION> 118 119 You can now use C<no> followed by a version number to specify that you 120 want to use a version of perl older than the specified one. 121 122 =head2 Recursive sort subs 123 124 You can now use recursive subroutines with sort(), thanks to Robin Houston. 125 126 =head2 Effect of pragmas in eval 127 128 The compile-time value of the C<%^H> hint variable can now propagate into 129 eval("")uated code. This makes it more useful to implement lexical 130 pragmas. 131 132 As a side-effect of this, the overloaded-ness of constants now propagates 133 into eval(""). 134 135 =head2 New B<-E> command-line switch 136 137 B<-E> is equivalent to B<-e>, but it implicitly enables all 138 optional features (like C<use feature ":5.10">). 139 140 =head2 C<chdir>, C<chmod> and C<chown> on filehandles 141 142 C<chdir>, C<chmod> and C<chown> can now work on filehandles as well as 143 filenames, if the system supports respectively C<fchdir>, C<fchmod> and 144 C<fchown>, thanks to a patch provided by Gisle Aas. 145 146 =head2 OS groups 147 148 C<$(> and C<$)> now return groups in the order where the OS returns them, 149 thanks to Gisle Aas. This wasn't previously the case. 150 151 =head1 Modules and Pragmata 152 153 =head2 New Core Modules 154 155 =over 4 156 157 =item * 158 159 A new pragma, C<feature>, has been added; see above in L</"Core 160 Enhancements">. 161 162 =item * 163 164 C<assertions::compat>, also available on CPAN, allows the use of assertions on 165 perl versions prior to 5.9.0 (that is the first one to natively support 166 them). 167 168 =item * 169 170 C<Math::BigInt::FastCalc> is an XS-enabled, and thus faster, version of 171 C<Math::BigInt::Calc>. 172 173 =item * 174 175 C<Compress::Zlib> is an interface to the zlib compression library. It 176 comes with a bundled version of zlib, so having a working zlib is not a 177 prerequisite to install it. It's used by C<Archive::Tar> (see below). 178 179 =item * 180 181 C<IO::Zlib> is an C<IO::>-style interface to C<Compress::Zlib>. 182 183 =item * 184 185 C<Archive::Tar> is a module to manipulate C<tar> archives. 186 187 =item * 188 189 C<Digest::SHA> is a module used to calculate many types of SHA digests, 190 has been included for SHA support in the CPAN module. 191 192 =item * 193 194 C<ExtUtils::CBuilder> and C<ExtUtils::ParseXS> have been added. 195 196 =back 197 198 =head1 Utility Changes 199 200 =head2 C<ptar> 201 202 C<ptar> is a pure perl implementation of C<tar>, that comes with 203 C<Archive::Tar>. 204 205 =head2 C<ptardiff> 206 207 C<ptardiff> is a small script used to generate a diff between the contents 208 of a tar archive and a directory tree. Like C<ptar>, it comes with 209 C<Archive::Tar>. 210 211 =head2 C<shasum> 212 213 This command-line utility, used to print or to check SHA digests, comes 214 with the new C<Digest::SHA> module. 215 216 =head2 C<h2xs> enhancements 217 218 C<h2xs> implements a new option C<--use-xsloader> to force use of 219 C<XSLoader> even in backwards compatible modules. 220 221 The handling of authors' names that had apostrophes has been fixed. 222 223 Any enums with negative values are now skipped. 224 225 =head2 C<perlivp> enhancements 226 227 C<perlivp> no longer checks for F<*.ph> files by default. Use the new C<-a> 228 option to run I<all> tests. 229 230 =head1 Documentation 231 232 =head2 Perl Glossary 233 234 The L<perlglossary> manpage is a glossary of terms used in the Perl 235 documentation, technical and otherwise, kindly provided by O'Reilly Media, 236 Inc. 237 238 L<perltodo> now lists a rough roadmap to Perl 5.10. 239 240 =head1 Performance Enhancements 241 242 =head2 XS-assisted SWASHGET 243 244 Some pure-perl code that perl was using to retrieve Unicode properties and 245 transliteration mappings has been reimplemented in XS. 246 247 =head2 Constant subroutines 248 249 The interpreter internals now support a far more memory efficient form of 250 inlineable constants. Storing a reference to a constant value in a symbol 251 table is equivalent to a full typeglob referencing a constant subroutine, 252 but using about 400 bytes less memory. This proxy constant subroutine is 253 automatically upgraded to a real typeglob with subroutine if necessary. 254 The approach taken is analogous to the existing space optimisation for 255 subroutine stub declarations, which are stored as plain scalars in place 256 of the full typeglob. 257 258 Several of the core modules have been converted to use this feature for 259 their system dependent constants - as a result C<use POSIX;> now takes about 260 200K less memory. 261 262 =head2 C<PERL_DONT_CREATE_GVSV> 263 264 The new compilation flag C<PERL_DONT_CREATE_GVSV>, introduced as an option 265 in perl 5.8.8, is turned on by default in perl 5.9.3. It prevents perl 266 from creating an empty scalar with every new typeglob. See L<perl588delta> 267 for details. 268 269 =head2 Weak references are cheaper 270 271 Weak reference creation is now I<O(1)> rather than I<O(n)>, courtesy of 272 Nicholas Clark. Weak reference deletion remains I<O(n)>, but if deletion only 273 happens at program exit, it may be skipped completely. 274 275 =head2 sort() enhancements 276 277 Salvador Fandiño provided improvements to reduce the memory usage of C<sort> 278 and to speed up some cases. 279 280 =head1 Installation and Configuration Improvements 281 282 =head2 Compilation improvements 283 284 Parallel makes should work properly now, although there may still be problems 285 if C<make test> is instructed to run in parallel. 286 287 Building with Borland's compilers on Win32 should work more smoothly. In 288 particular Steve Hay has worked to side step many warnings emitted by their 289 compilers and at least one C compiler internal error. 290 291 Perl extensions on Windows now can be statically built into the Perl DLL, 292 thanks to a work by Vadim Konovalov. 293 294 =head2 New Or Improved Platforms 295 296 Perl is being ported to Symbian OS. See L<perlsymbian> for more 297 information. 298 299 The VMS port has been improved. See L<perlvms>. 300 301 DynaLoader::dl_unload_file() now works on Windows. 302 303 Portability of Perl on various recent compilers on Windows has been 304 improved (Borland C++, Visual C++ 7.0). 305 306 =head2 New probes 307 308 C<Configure> will now detect C<clearenv> and C<unsetenv>, thanks to a 309 patch from Alan Burlison. It will also probe for C<futimes> (and use it 310 internally if available), and whether C<sprintf> correctly returns the 311 length of the formatted string. 312 313 =head2 Module auxiliary files 314 315 README files and changelogs for CPAN modules bundled with perl are no 316 longer installed. 317 318 =head1 Selected Bug Fixes 319 320 =head2 C<defined $$x> 321 322 C<use strict "refs"> was ignoring taking a hard reference in an argument 323 to defined(), as in : 324 325 use strict "refs"; 326 my $x = "foo"; 327 if (defined $$x) {...} 328 329 This now correctly produces the run-time error C<Can't use string as a 330 SCALAR ref while "strict refs" in use>. (However, C<defined @$foo> and 331 C<defined %$foo> are still allowed. Those constructs are discouraged 332 anyway.) 333 334 =head2 Calling CORE::require() 335 336 CORE::require() and CORE::do() were always parsed as require() and do() 337 when they were overridden. This is now fixed. 338 339 =head2 Subscripts of slices 340 341 You can now use a non-arrowed form for chained subscripts after a list 342 slice, like in: 343 344 ({foo => "bar"})[0]{foo} 345 346 This used to be a syntax error; a C<< -> >> was required. 347 348 =head2 Remove over-optimisation 349 350 Perl 5.9.2 introduced a change so that assignments of C<undef> to a 351 scalar, or of an empty list to an array or a hash, were optimised out. As 352 this could cause problems when C<goto> jumps were involved, this change 353 was backed out. 354 355 =head2 sprintf() fixes 356 357 Using the sprintf() function with some formats could lead to a buffer 358 overflow in some specific cases. This has been fixed, along with several 359 other bugs, notably in bounds checking. 360 361 In related fixes, it was possible for badly written code that did not follow 362 the documentation of C<Sys::Syslog> to have formatting vulnerabilities. 363 C<Sys::Syslog> has been changed to protect people from poor quality third 364 party code. 365 366 =head2 no warnings 'category' works correctly with -w 367 368 Previously when running with warnings enabled globally via C<-w>, selective 369 disabling of specific warning categories would actually turn off all warnings. 370 This is now fixed; now C<no warnings 'io';> will only turn off warnings in the 371 C<io> class. Previously it would erroneously turn off all warnings. 372 373 =head2 Smaller fixes 374 375 =over 4 376 377 =item * 378 379 C<FindBin> now works better with directories where access rights are more 380 restrictive than usual. 381 382 =item * 383 384 Several memory leaks in ithreads were closed. Also, ithreads were made 385 less memory-intensive. 386 387 =item * 388 389 Trailing spaces are now trimmed from C<$!> and C<$^E>. 390 391 =item * 392 393 Operations that require perl to read a process' list of groups, such as reads 394 of C<$(> and C<$)>, now dynamically allocate memory rather than using a 395 fixed sized array. The fixed size array could cause C stack exhaustion on 396 systems configured to use large numbers of groups. 397 398 =item * 399 400 C<PerlIO::scalar> now works better with non-default C<$/> settings. 401 402 =item * 403 404 The C<x> repetition operator is now able to operate on C<qw//> lists. This 405 used to raise a syntax error. 406 407 =item * 408 409 The debugger now traces correctly execution in eval("")uated code that 410 contains #line directives. 411 412 =item * 413 414 The value of the C<open> pragma is no longer ignored for three-argument 415 opens. 416 417 =item * 418 419 Perl will now use the C library calls C<unsetenv> and C<clearenv> if present 420 to delete keys from C<%ENV> and delete C<%ENV> entirely, thanks to a patch 421 from Alan Burlison. 422 423 =back 424 425 =head2 More Unicode Fixes 426 427 =over 4 428 429 =item * 430 431 chr() on a negative value now gives C<\x{FFFD}>, the Unicode replacement 432 character, unless when the C<bytes> pragma is in effect, where the low 433 eight bytes of the value are used. 434 435 =item * 436 437 Some case insensitive matches between UTF-8 encoded data and 8 bit regexps, 438 and vice versa, could give malformed character warnings. These have been 439 fixed by Dave Mitchell and Yves Orton. 440 441 =item * 442 443 C<lcfirst> and C<ucfirst> could corrupt the string for certain cases where 444 the length UTF-8 encoding of the string in lower case, upper case or title 445 case differed. This was fixed by Nicholas Clark. 446 447 =back 448 449 =head1 New or Changed Diagnostics 450 451 =head2 Attempt to set length of freed array 452 453 This is a new warning, produced in situations like the following one: 454 455 $r = do {my @a; \$#a}; 456 $$r = 503; 457 458 =head2 Non-string passed as bitmask 459 460 This is a new warning, produced when number has been passed as a argument to 461 select(), instead of a bitmask. 462 463 # Wrong, will now warn 464 $rin = fileno(STDIN); 465 ($nfound,$timeleft) = select($rout=$rin, undef, undef, $timeout); 466 467 # Should be 468 $rin = ''; 469 vec($rin,fileno(STDIN),1) = 1; 470 ($nfound,$timeleft) = select($rout=$rin, undef, undef, $timeout); 471 472 =head2 Search pattern not terminated or ternary operator parsed as search pattern 473 474 This syntax error indicates that the lexer couldn't find the final 475 delimiter of a C<?PATTERN?> construct. Mentioning the ternary operator in 476 this error message makes syntax diagnostic easier. 477 478 =head2 "%s" variable %s masks earlier declaration 479 480 This warning is now emitted in more consistent cases; in short, when one 481 of the declarations involved is a C<my> variable: 482 483 my $x; my $x; # warns 484 my $x; our $x; # warns 485 our $x; my $x; # warns 486 487 On the other hand, the following: 488 489 our $x; our $x; 490 491 now gives a C<"our" variable %s redeclared> warning. 492 493 =head2 readdir()/closedir()/etc. attempted on invalid dirhandle 494 495 These new warnings are now emitted when a dirhandle is used but is 496 either closed or not really a dirhandle. 497 498 =head1 Changed Internals 499 500 In general, the source code of perl has been refactored, tied up, and 501 optimized in many places. Also, memory management and allocation has been 502 improved in a couple of points. 503 504 Andy Lester supplied many improvements to determine which function 505 parameters and local variables could actually be declared C<const> to the C 506 compiler. Steve Peters provided new C<*_set> macros and reworked the core to 507 use these rather than assigning to macros in LVALUE context. 508 509 Dave Mitchell improved the lexer debugging output under C<-DT>. 510 511 A new file, F<mathoms.c>, has been added. It contains functions that are 512 no longer used in the perl core, but that remain available for binary or 513 source compatibility reasons. However, those functions will not be 514 compiled in if you add C<-DNO_MATHOMS> in the compiler flags. 515 516 The C<AvFLAGS> macro has been removed. 517 518 The C<av_*()> functions, used to manipulate arrays, no longer accept null 519 C<AV*> parameters. 520 521 =head2 B:: modules inheritance changed 522 523 The inheritance hierarchy of C<B::> modules has changed; C<B::NV> now 524 inherits from C<B::SV> (it used to inherit from C<B::IV>). 525 526 =head1 Reporting Bugs 527 528 If you find what you think is a bug, you might check the articles 529 recently posted to the comp.lang.perl.misc newsgroup and the perl 530 bug database at http://bugs.perl.org/ . There may also be 531 information at http://www.perl.org/ , the Perl Home Page. 532 533 If you believe you have an unreported bug, please run the B<perlbug> 534 program included with your release. Be sure to trim your bug down 535 to a tiny but sufficient test case. Your bug report, along with the 536 output of C<perl -V>, will be sent off to perlbug@perl.org to be 537 analysed by the Perl porting team. 538 539 =head1 SEE ALSO 540 541 The F<Changes> file for exhaustive details on what changed. 542 543 The F<INSTALL> file for how to build Perl. 544 545 The F<README> file for general stuff. 546 547 The F<Artistic> and F<Copying> files for copyright information. 548 549 =cut
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