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   1  =head1 NAME
   2  
   3  perl581delta - what is new for perl v5.8.1
   4  
   5  =head1 DESCRIPTION
   6  
   7  This document describes differences between the 5.8.0 release and
   8  the 5.8.1 release.
   9  
  10  If you are upgrading from an earlier release such as 5.6.1, first read
  11  the L<perl58delta>, which describes differences between 5.6.0 and
  12  5.8.0.
  13  
  14  In case you are wondering about 5.6.1, it was bug-fix-wise rather
  15  identical to the development release 5.7.1.  Confused?  This timeline
  16  hopefully helps a bit: it lists the new major releases, their maintenance
  17  releases, and the development releases.
  18  
  19            New     Maintenance  Development
  20  
  21            5.6.0                             2000-Mar-22
  22                                 5.7.0        2000-Sep-02
  23                    5.6.1                     2001-Apr-08
  24                                 5.7.1        2001-Apr-09
  25                                 5.7.2        2001-Jul-13
  26                                 5.7.3        2002-Mar-05
  27            5.8.0                             2002-Jul-18
  28                    5.8.1                     2003-Sep-25
  29  
  30  =head1 Incompatible Changes
  31  
  32  =head2 Hash Randomisation
  33  
  34  Mainly due to security reasons, the "random ordering" of hashes
  35  has been made even more random.  Previously while the order of hash
  36  elements from keys(), values(), and each() was essentially random,
  37  it was still repeatable.  Now, however, the order varies between
  38  different runs of Perl.
  39  
  40  B<Perl has never guaranteed any ordering of the hash keys>, and the
  41  ordering has already changed several times during the lifetime of
  42  Perl 5.  Also, the ordering of hash keys has always been, and
  43  continues to be, affected by the insertion order.
  44  
  45  The added randomness may affect applications.
  46  
  47  One possible scenario is when output of an application has included
  48  hash data.  For example, if you have used the Data::Dumper module to
  49  dump data into different files, and then compared the files to see
  50  whether the data has changed, now you will have false positives since
  51  the order in which hashes are dumped will vary.  In general the cure
  52  is to sort the keys (or the values); in particular for Data::Dumper to
  53  use the C<Sortkeys> option.  If some particular order is really
  54  important, use tied hashes: for example the Tie::IxHash module
  55  which by default preserves the order in which the hash elements
  56  were added.
  57  
  58  More subtle problem is reliance on the order of "global destruction".
  59  That is what happens at the end of execution: Perl destroys all data
  60  structures, including user data.  If your destructors (the DESTROY
  61  subroutines) have assumed any particular ordering to the global
  62  destruction, there might be problems ahead.  For example, in a
  63  destructor of one object you cannot assume that objects of any other
  64  class are still available, unless you hold a reference to them.
  65  If the environment variable PERL_DESTRUCT_LEVEL is set to a non-zero
  66  value, or if Perl is exiting a spawned thread, it will also destruct
  67  the ordinary references and the symbol tables that are no longer in use.
  68  You can't call a class method or an ordinary function on a class that
  69  has been collected that way.
  70  
  71  The hash randomisation is certain to reveal hidden assumptions about
  72  some particular ordering of hash elements, and outright bugs: it
  73  revealed a few bugs in the Perl core and core modules.
  74  
  75  To disable the hash randomisation in runtime, set the environment
  76  variable PERL_HASH_SEED to 0 (zero) before running Perl (for more
  77  information see L<perlrun/PERL_HASH_SEED>), or to disable the feature
  78  completely in compile time, compile with C<-DNO_HASH_SEED> (see F<INSTALL>).
  79  
  80  See L<perlsec/"Algorithmic Complexity Attacks"> for the original
  81  rationale behind this change.
  82  
  83  =head2 UTF-8 On Filehandles No Longer Activated By Locale
  84  
  85  In Perl 5.8.0 all filehandles, including the standard filehandles,
  86  were implicitly set to be in Unicode UTF-8 if the locale settings
  87  indicated the use of UTF-8.  This feature caused too many problems,
  88  so the feature was turned off and redesigned: see L</"Core Enhancements">.
  89  
  90  =head2 Single-number v-strings are no longer v-strings before "=>"
  91  
  92  The version strings or v-strings (see L<perldata/"Version Strings">)
  93  feature introduced in Perl 5.6.0 has been a source of some confusion--
  94  especially when the user did not want to use it, but Perl thought it
  95  knew better.  Especially troublesome has been the feature that before
  96  a "=>" a version string (a "v" followed by digits) has been interpreted
  97  as a v-string instead of a string literal.  In other words:
  98  
  99      %h = ( v65 => 42 );
 100  
 101  has meant since Perl 5.6.0
 102  
 103      %h = ( 'A' => 42 );
 104  
 105  (at least in platforms of ASCII progeny)  Perl 5.8.1 restores the
 106  more natural interpretation
 107  
 108      %h = ( 'v65' => 42 );
 109  
 110  The multi-number v-strings like v65.66 and 65.66.67 still continue to
 111  be v-strings in Perl 5.8.
 112  
 113  =head2 (Win32) The -C Switch Has Been Repurposed
 114  
 115  The -C switch has changed in an incompatible way.  The old semantics
 116  of this switch only made sense in Win32 and only in the "use utf8"
 117  universe in 5.6.x releases, and do not make sense for the Unicode
 118  implementation in 5.8.0.  Since this switch could not have been used
 119  by anyone, it has been repurposed.  The behavior that this switch
 120  enabled in 5.6.x releases may be supported in a transparent,
 121  data-dependent fashion in a future release.
 122  
 123  For the new life of this switch, see L<"UTF-8 no longer default under
 124  UTF-8 locales">, and L<perlrun/-C>.
 125  
 126  =head2 (Win32) The /d Switch Of cmd.exe
 127  
 128  Perl 5.8.1 uses the /d switch when running the cmd.exe shell
 129  internally for system(), backticks, and when opening pipes to external
 130  programs.  The extra switch disables the execution of AutoRun commands
 131  from the registry, which is generally considered undesirable when
 132  running external programs.  If you wish to retain compatibility with
 133  the older behavior, set PERL5SHELL in your environment to C<cmd /x/c>.
 134  
 135  =head1 Core Enhancements
 136  
 137  =head2 UTF-8 no longer default under UTF-8 locales
 138  
 139  In Perl 5.8.0 many Unicode features were introduced.   One of them
 140  was found to be of more nuisance than benefit: the automagic
 141  (and silent) "UTF-8-ification" of filehandles, including the
 142  standard filehandles, if the user's locale settings indicated
 143  use of UTF-8.
 144  
 145  For example, if you had C<en_US.UTF-8> as your locale, your STDIN and
 146  STDOUT were automatically "UTF-8", in other words an implicit
 147  binmode(..., ":utf8") was made.  This meant that trying to print, say,
 148  chr(0xff), ended up printing the bytes 0xc3 0xbf.  Hardly what
 149  you had in mind unless you were aware of this feature of Perl 5.8.0.
 150  The problem is that the vast majority of people weren't: for example
 151  in RedHat releases 8 and 9 the B<default> locale setting is UTF-8, so
 152  all RedHat users got UTF-8 filehandles, whether they wanted it or not.
 153  The pain was intensified by the Unicode implementation of Perl 5.8.0
 154  (still) having nasty bugs, especially related to the use of s/// and
 155  tr///.  (Bugs that have been fixed in 5.8.1)
 156  
 157  Therefore a decision was made to backtrack the feature and change it
 158  from implicit silent default to explicit conscious option.  The new
 159  Perl command line option C<-C> and its counterpart environment
 160  variable PERL_UNICODE can now be used to control how Perl and Unicode
 161  interact at interfaces like I/O and for example the command line
 162  arguments.  See L<perlrun/-C> and L<perlrun/PERL_UNICODE> for more
 163  information.
 164  
 165  =head2 Unsafe signals again available
 166  
 167  In Perl 5.8.0 the so-called "safe signals" were introduced.  This
 168  means that Perl no longer handles signals immediately but instead
 169  "between opcodes", when it is safe to do so.  The earlier immediate
 170  handling easily could corrupt the internal state of Perl, resulting
 171  in mysterious crashes.
 172  
 173  However, the new safer model has its problems too.  Because now an
 174  opcode, a basic unit of Perl execution, is never interrupted but
 175  instead let to run to completion, certain operations that can take a
 176  long time now really do take a long time.  For example, certain
 177  network operations have their own blocking and timeout mechanisms, and
 178  being able to interrupt them immediately would be nice.
 179  
 180  Therefore perl 5.8.1 introduces a "backdoor" to restore the pre-5.8.0
 181  (pre-5.7.3, really) signal behaviour.  Just set the environment variable
 182  PERL_SIGNALS to C<unsafe>, and the old immediate (and unsafe)
 183  signal handling behaviour returns.  See L<perlrun/PERL_SIGNALS>
 184  and L<perlipc/"Deferred Signals (Safe Signals)">.
 185  
 186  In completely unrelated news, you can now use safe signals with
 187  POSIX::SigAction.  See L<POSIX/POSIX::SigAction>.
 188  
 189  =head2 Tied Arrays with Negative Array Indices
 190  
 191  Formerly, the indices passed to C<FETCH>, C<STORE>, C<EXISTS>, and
 192  C<DELETE> methods in tied array class were always non-negative.  If
 193  the actual argument was negative, Perl would call FETCHSIZE implicitly
 194  and add the result to the index before passing the result to the tied
 195  array method.  This behaviour is now optional.  If the tied array class
 196  contains a package variable named C<$NEGATIVE_INDICES> which is set to
 197  a true value, negative values will be passed to C<FETCH>, C<STORE>,
 198  C<EXISTS>, and C<DELETE> unchanged.
 199  
 200  =head2 local ${$x}
 201  
 202  The syntaxes
 203  
 204      local ${$x}
 205      local @{$x}
 206      local %{$x}
 207  
 208  now do localise variables, given that the $x is a valid variable name.
 209  
 210  =head2 Unicode Character Database 4.0.0
 211  
 212  The copy of the Unicode Character Database included in Perl 5.8 has
 213  been updated to 4.0.0 from 3.2.0.  This means for example that the
 214  Unicode character properties are as in Unicode 4.0.0.
 215  
 216  =head2 Deprecation Warnings
 217  
 218  There is one new feature deprecation.  Perl 5.8.0 forgot to add
 219  some deprecation warnings, these warnings have now been added.
 220  Finally, a reminder of an impending feature removal.
 221  
 222  =head3 (Reminder) Pseudo-hashes are deprecated (really)
 223  
 224  Pseudo-hashes were deprecated in Perl 5.8.0 and will be removed in
 225  Perl 5.10.0, see L<perl58delta> for details.  Each attempt to access
 226  pseudo-hashes will trigger the warning C<Pseudo-hashes are deprecated>.
 227  If you really want to continue using pseudo-hashes but not to see the
 228  deprecation warnings, use:
 229  
 230      no warnings 'deprecated';
 231  
 232  Or you can continue to use the L<fields> pragma, but please don't
 233  expect the data structures to be pseudohashes any more.
 234  
 235  =head3 (Reminder) 5.005-style threads are deprecated (really)
 236  
 237  5.005-style threads (activated by C<use Thread;>) were deprecated in
 238  Perl 5.8.0 and will be removed after Perl 5.8, see L<perl58delta> for
 239  details.  Each 5.005-style thread creation will trigger the warning
 240  C<5.005 threads are deprecated>.  If you really want to continue
 241  using the 5.005 threads but not to see the deprecation warnings, use:
 242  
 243      no warnings 'deprecated';
 244  
 245  =head3 (Reminder) The $* variable is deprecated (really)
 246  
 247  The C<$*> variable controlling multi-line matching has been deprecated
 248  and will be removed after 5.8.  The variable has been deprecated for a
 249  long time, and a deprecation warning C<Use of $* is deprecated> is given,
 250  now the variable will just finally be removed.  The functionality has
 251  been supplanted by the C</s> and C</m> modifiers on pattern matching.
 252  If you really want to continue using the C<$*>-variable but not to see
 253  the deprecation warnings, use:
 254  
 255      no warnings 'deprecated';
 256  
 257  =head2 Miscellaneous Enhancements
 258  
 259  C<map> in void context is no longer expensive. C<map> is now context
 260  aware, and will not construct a list if called in void context.
 261  
 262  If a socket gets closed by the server while printing to it, the client
 263  now gets a SIGPIPE.  While this new feature was not planned, it fell
 264  naturally out of PerlIO changes, and is to be considered an accidental
 265  feature.
 266  
 267  PerlIO::get_layers(FH) returns the names of the PerlIO layers
 268  active on a filehandle.
 269  
 270  PerlIO::via layers can now have an optional UTF8 method to
 271  indicate whether the layer wants to "auto-:utf8" the stream.
 272  
 273  utf8::is_utf8() has been added as a quick way to test whether
 274  a scalar is encoded internally in UTF-8 (Unicode).
 275  
 276  =head1 Modules and Pragmata
 277  
 278  =head2 Updated Modules And Pragmata
 279  
 280  The following modules and pragmata have been updated since Perl 5.8.0:
 281  
 282  =over 4
 283  
 284  =item base
 285  
 286  =item B::Bytecode
 287  
 288  In much better shape than it used to be.  Still far from perfect, but
 289  maybe worth a try.
 290  
 291  =item B::Concise
 292  
 293  =item B::Deparse
 294  
 295  =item Benchmark
 296  
 297  An optional feature, C<:hireswallclock>, now allows for high
 298  resolution wall clock times (uses Time::HiRes).
 299  
 300  =item ByteLoader
 301  
 302  See B::Bytecode.
 303  
 304  =item bytes
 305  
 306  Now has bytes::substr.
 307  
 308  =item CGI
 309  
 310  =item charnames
 311  
 312  One can now have custom character name aliases.
 313  
 314  =item CPAN
 315  
 316  There is now a simple command line frontend to the CPAN.pm
 317  module called F<cpan>.
 318  
 319  =item Data::Dumper
 320  
 321  A new option, Pair, allows choosing the separator between hash keys
 322  and values.
 323  
 324  =item DB_File
 325  
 326  =item Devel::PPPort
 327  
 328  =item Digest::MD5
 329  
 330  =item Encode
 331  
 332  Significant updates on the encoding pragma functionality
 333  (tr/// and the DATA filehandle, formats).
 334  
 335  If a filehandle has been marked as to have an encoding, unmappable
 336  characters are detected already during input, not later (when the
 337  corrupted data is being used).
 338  
 339  The ISO 8859-6 conversion table has been corrected (the 0x30..0x39
 340  erroneously mapped to U+0660..U+0669, instead of U+0030..U+0039).  The
 341  GSM 03.38 conversion did not handle escape sequences correctly.  The
 342  UTF-7 encoding has been added (making Encode feature-complete with
 343  Unicode::String).
 344  
 345  =item fields
 346  
 347  =item libnet
 348  
 349  =item Math::BigInt
 350  
 351  A lot of bugs have been fixed since v1.60, the version included in Perl
 352  v5.8.0. Especially noteworthy are the bug in Calc that caused div and mod to
 353  fail for some large values, and the fixes to the handling of bad inputs.
 354  
 355  Some new features were added, e.g. the broot() method, you can now pass
 356  parameters to config() to change some settings at runtime, and it is now
 357  possible to trap the creation of NaN and infinity.
 358  
 359  As usual, some optimizations took place and made the math overall a tad
 360  faster. In some cases, quite a lot faster, actually. Especially alternative
 361  libraries like Math::BigInt::GMP benefit from this. In addition, a lot of the
 362  quite clunky routines like fsqrt() and flog() are now much much faster.
 363  
 364  =item MIME::Base64
 365  
 366  =item NEXT
 367  
 368  Diamond inheritance now works.
 369  
 370  =item Net::Ping
 371  
 372  =item PerlIO::scalar
 373  
 374  Reading from non-string scalars (like the special variables, see
 375  L<perlvar>) now works.
 376  
 377  =item podlators
 378  
 379  =item Pod::LaTeX
 380  
 381  =item PodParsers
 382  
 383  =item Pod::Perldoc
 384  
 385  Complete rewrite.  As a side-effect, no longer refuses to startup when
 386  run by root.
 387  
 388  =item Scalar::Util
 389  
 390  New utilities: refaddr, isvstring, looks_like_number, set_prototype.
 391  
 392  =item Storable
 393  
 394  Can now store code references (via B::Deparse, so not foolproof).
 395  
 396  =item strict
 397  
 398  Earlier versions of the strict pragma did not check the parameters
 399  implicitly passed to its "import" (use) and "unimport" (no) routine.
 400  This caused the false idiom such as:
 401  
 402          use strict qw(@ISA);
 403          @ISA = qw(Foo);
 404  
 405  This however (probably) raised the false expectation that the strict
 406  refs, vars and subs were being enforced (and that @ISA was somehow
 407  "declared").  But the strict refs, vars, and subs are B<not> enforced
 408  when using this false idiom.
 409  
 410  Starting from Perl 5.8.1, the above B<will> cause an error to be
 411  raised.  This may cause programs which used to execute seemingly
 412  correctly without warnings and errors to fail when run under 5.8.1.
 413  This happens because
 414  
 415          use strict qw(@ISA);
 416  
 417  will now fail with the error:
 418  
 419          Unknown 'strict' tag(s) '@ISA'
 420  
 421  The remedy to this problem is to replace this code with the correct idiom:
 422  
 423          use strict;
 424          use vars qw(@ISA);
 425          @ISA = qw(Foo);
 426  
 427  =item Term::ANSIcolor
 428  
 429  =item Test::Harness
 430  
 431  Now much more picky about extra or missing output from test scripts.
 432  
 433  =item Test::More
 434  
 435  =item Test::Simple
 436  
 437  =item Text::Balanced
 438  
 439  =item Time::HiRes
 440  
 441  Use of nanosleep(), if available, allows mixing subsecond sleeps with
 442  alarms.
 443  
 444  =item threads
 445  
 446  Several fixes, for example for join() problems and memory
 447  leaks.  In some platforms (like Linux) that use glibc the minimum memory
 448  footprint of one ithread has been reduced by several hundred kilobytes.
 449  
 450  =item threads::shared
 451  
 452  Many memory leaks have been fixed.
 453  
 454  =item Unicode::Collate
 455  
 456  =item Unicode::Normalize
 457  
 458  =item Win32::GetFolderPath
 459  
 460  =item Win32::GetOSVersion
 461  
 462  Now returns extra information.
 463  
 464  =back
 465  
 466  =head1 Utility Changes
 467  
 468  The C<h2xs> utility now produces a more modern layout:
 469  F<Foo-Bar/lib/Foo/Bar.pm> instead of F<Foo/Bar/Bar.pm>.
 470  Also, the boilerplate test is now called F<t/Foo-Bar.t>
 471  instead of F<t/1.t>.
 472  
 473  The Perl debugger (F<lib/perl5db.pl>) has now been extensively
 474  documented and bugs found while documenting have been fixed.
 475  
 476  C<perldoc> has been rewritten from scratch to be more robust and
 477  feature rich.
 478  
 479  C<perlcc -B> works now at least somewhat better, while C<perlcc -c>
 480  is rather more broken.  (The Perl compiler suite as a whole continues
 481  to be experimental.)
 482  
 483  =head1 New Documentation
 484  
 485  perl573delta has been added to list the differences between the
 486  (now quite obsolete) development releases 5.7.2 and 5.7.3.
 487  
 488  perl58delta has been added: it is the perldelta of 5.8.0, detailing
 489  the differences between 5.6.0 and 5.8.0.
 490  
 491  perlartistic has been added: it is the Artistic License in pod format,
 492  making it easier for modules to refer to it.
 493  
 494  perlcheat has been added: it is a Perl cheat sheet.
 495  
 496  perlgpl has been added: it is the GNU General Public License in pod
 497  format, making it easier for modules to refer to it.
 498  
 499  perlmacosx has been added to tell about the installation and use
 500  of Perl in Mac OS X.
 501  
 502  perlos400 has been added to tell about the installation and use
 503  of Perl in OS/400 PASE.
 504  
 505  perlreref has been added: it is a regular expressions quick reference.
 506  
 507  =head1 Installation and Configuration Improvements
 508  
 509  The UNIX standard Perl location, F</usr/bin/perl>, is no longer
 510  overwritten by default if it exists.  This change was very prudent
 511  because so many UNIX vendors already provide a F</usr/bin/perl>,
 512  but simultaneously many system utilities may depend on that
 513  exact version of Perl, so better not to overwrite it.
 514  
 515  One can now specify installation directories for site and vendor man
 516  and HTML pages, and site and vendor scripts.  See F<INSTALL>.
 517  
 518  One can now specify a destination directory for Perl installation
 519  by specifying the DESTDIR variable for C<make install>.  (This feature
 520  is slightly different from the previous C<Configure -Dinstallprefix=...>.)
 521  See F<INSTALL>.
 522  
 523  gcc versions 3.x introduced a new warning that caused a lot of noise
 524  during Perl compilation: C<gcc -Ialreadyknowndirectory (warning:
 525  changing search order)>.  This warning has now been avoided by
 526  Configure weeding out such directories before the compilation.
 527  
 528  One can now build subsets of Perl core modules by using the
 529  Configure flags C<-Dnoextensions=...> and C<-Donlyextensions=...>,
 530  see F<INSTALL>.
 531  
 532  =head2 Platform-specific enhancements
 533  
 534  In Cygwin Perl can now be built with threads (C<Configure -Duseithreads>).
 535  This works with both Cygwin 1.3.22 and Cygwin 1.5.3.
 536  
 537  In newer FreeBSD releases Perl 5.8.0 compilation failed because of
 538  trying to use F<malloc.h>, which in FreeBSD is just a dummy file, and
 539  a fatal error to even try to use.  Now F<malloc.h> is not used.
 540  
 541  Perl is now known to build also in Hitachi HI-UXMPP.
 542  
 543  Perl is now known to build again in LynxOS.
 544  
 545  Mac OS X now installs with Perl version number embedded in
 546  installation directory names for easier upgrading of user-compiled
 547  Perl, and the installation directories in general are more standard.
 548  In other words, the default installation no longer breaks the
 549  Apple-provided Perl.  On the other hand, with C<Configure -Dprefix=/usr>
 550  you can now really replace the Apple-supplied Perl (B<please be careful>).
 551  
 552  Mac OS X now builds Perl statically by default.  This change was done
 553  mainly for faster startup times.  The Apple-provided Perl is still
 554  dynamically linked and shared, and you can enable the sharedness for
 555  your own Perl builds by C<Configure -Duseshrplib>.
 556  
 557  Perl has been ported to IBM's OS/400 PASE environment.  The best way
 558  to build a Perl for PASE is to use an AIX host as a cross-compilation
 559  environment.  See README.os400.
 560  
 561  Yet another cross-compilation option has been added: now Perl builds
 562  on OpenZaurus, an Linux distribution based on Mandrake + Embedix for
 563  the Sharp Zaurus PDA.  See the Cross/README file.
 564  
 565  Tru64 when using gcc 3 drops the optimisation for F<toke.c> to C<-O2>
 566  because of gigantic memory use with the default C<-O3>.
 567  
 568  Tru64 can now build Perl with the newer Berkeley DBs.
 569  
 570  Building Perl on WinCE has been much enhanced, see F<README.ce>
 571  and F<README.perlce>.
 572  
 573  =head1 Selected Bug Fixes
 574  
 575  =head2 Closures, eval and lexicals
 576  
 577  There have been many fixes in the area of anonymous subs, lexicals and
 578  closures.  Although this means that Perl is now more "correct", it is
 579  possible that some existing code will break that happens to rely on
 580  the faulty behaviour.  In practice this is unlikely unless your code
 581  contains a very complex nesting of anonymous subs, evals and lexicals.
 582  
 583  =head2 Generic fixes
 584  
 585  If an input filehandle is marked C<:utf8> and Perl sees illegal UTF-8
 586  coming in when doing C<< <FH> >>, if warnings are enabled a warning is
 587  immediately given - instead of being silent about it and Perl being
 588  unhappy about the broken data later.  (The C<:encoding(utf8)> layer
 589  also works the same way.)
 590  
 591  binmode(SOCKET, ":utf8") only worked on the input side, not on the
 592  output side of the socket.  Now it works both ways.
 593  
 594  For threaded Perls certain system database functions like getpwent()
 595  and getgrent() now grow their result buffer dynamically, instead of
 596  failing.  This means that at sites with lots of users and groups the
 597  functions no longer fail by returning only partial results.
 598  
 599  Perl 5.8.0 had accidentally broken the capability for users
 600  to define their own uppercase<->lowercase Unicode mappings
 601  (as advertised by the Camel).  This feature has been fixed and
 602  is also documented better.
 603  
 604  In 5.8.0 this
 605  
 606      $some_unicode .= <FH>;
 607  
 608  didn't work correctly but instead corrupted the data.  This has now
 609  been fixed.
 610  
 611  Tied methods like FETCH etc. may now safely access tied values, i.e.
 612  resulting in a recursive call to FETCH etc.  Remember to break the
 613  recursion, though.
 614  
 615  At startup Perl blocks the SIGFPE signal away since there isn't much
 616  Perl can do about it.  Previously this blocking was in effect also for
 617  programs executed from within Perl.  Now Perl restores the original
 618  SIGFPE handling routine, whatever it was, before running external
 619  programs.
 620  
 621  Linenumbers in Perl scripts may now be greater than 65536, or 2**16.
 622  (Perl scripts have always been able to be larger than that, it's just
 623  that the linenumber for reported errors and warnings have "wrapped
 624  around".)  While scripts that large usually indicate a need to rethink
 625  your code a bit, such Perl scripts do exist, for example as results
 626  from generated code.  Now linenumbers can go all the way to
 627  4294967296, or 2**32.
 628  
 629  =head2 Platform-specific fixes
 630  
 631  Linux
 632  
 633  =over 4
 634  
 635  =item *
 636  
 637  Setting $0 works again (with certain limitations that
 638  Perl cannot do much about: see L<perlvar/$0>)
 639  
 640  =back
 641  
 642  HP-UX
 643  
 644  =over 4
 645  
 646  =item *
 647  
 648  Setting $0 now works.
 649  
 650  =back
 651  
 652  VMS
 653  
 654  =over 4
 655  
 656  =item *
 657  
 658  Configuration now tests for the presence of C<poll()>, and IO::Poll
 659  now uses the vendor-supplied function if detected.
 660  
 661  =item *
 662  
 663  A rare access violation at Perl start-up could occur if the Perl image was
 664  installed with privileges or if there was an identifier with the
 665  subsystem attribute set in the process's rightslist.  Either of these
 666  circumstances triggered tainting code that contained a pointer bug. 
 667  The faulty pointer arithmetic has been fixed.
 668  
 669  =item *
 670  
 671  The length limit on values (not keys) in the %ENV hash has been raised
 672  from 255 bytes to 32640 bytes (except when the PERL_ENV_TABLES setting
 673  overrides the default use of logical names for %ENV).  If it is
 674  necessary to access these long values from outside Perl, be aware that
 675  they are implemented using search list logical names that store the
 676  value in pieces, each 255-byte piece (up to 128 of them) being an
 677  element in the search list. When doing a lookup in %ENV from within
 678  Perl, the elements are combined into a single value.  The existing
 679  VMS-specific ability to access individual elements of a search list
 680  logical name via the $ENV{'foo;N'} syntax (where N is the search list
 681  index) is unimpaired.
 682  
 683  =item *
 684  
 685  The piping implementation now uses local rather than global DCL
 686  symbols for inter-process communication.
 687  
 688  =item *
 689  
 690  File::Find could become confused when navigating to a relative
 691  directory whose name collided with a logical name.  This problem has
 692  been corrected by adding directory syntax to relative path names, thus
 693  preventing logical name translation.
 694  
 695  =back
 696  
 697  Win32
 698  
 699  =over 4
 700  
 701  =item *
 702  
 703  A memory leak in the fork() emulation has been fixed.
 704  
 705  =item *
 706  
 707  The return value of the ioctl() built-in function was accidentally
 708  broken in 5.8.0.  This has been corrected.
 709  
 710  =item *
 711  
 712  The internal message loop executed by perl during blocking operations
 713  sometimes interfered with messages that were external to Perl.
 714  This often resulted in blocking operations terminating prematurely or
 715  returning incorrect results, when Perl was executing under environments
 716  that could generate Windows messages.  This has been corrected.
 717  
 718  =item *
 719  
 720  Pipes and sockets are now automatically in binary mode.
 721  
 722  =item *
 723  
 724  The four-argument form of select() did not preserve $! (errno) properly
 725  when there were errors in the underlying call.  This is now fixed.
 726  
 727  =item *
 728  
 729  The "CR CR LF" problem of has been fixed, binmode(FH, ":crlf")
 730  is now effectively a no-op.
 731  
 732  =back
 733  
 734  =head1 New or Changed Diagnostics
 735  
 736  All the warnings related to pack() and unpack() were made more
 737  informative and consistent.
 738  
 739  =head2 Changed "A thread exited while %d threads were running"
 740  
 741  The old version
 742  
 743      A thread exited while %d other threads were still running
 744  
 745  was misleading because the "other" included also the thread giving
 746  the warning.
 747  
 748  =head2 Removed "Attempt to clear a restricted hash"
 749  
 750  It is not illegal to clear a restricted hash, so the warning
 751  was removed.
 752  
 753  =head2 New "Illegal declaration of anonymous subroutine"
 754  
 755  You must specify the block of code for C<sub>.
 756  
 757  =head2 Changed "Invalid range "%s" in transliteration operator"
 758  
 759  The old version
 760  
 761      Invalid [] range "%s" in transliteration operator
 762  
 763  was simply wrong because there are no "[] ranges" in tr///.
 764  
 765  =head2 New "Missing control char name in \c"
 766  
 767  Self-explanatory.
 768  
 769  =head2 New "Newline in left-justified string for %s"
 770  
 771  The padding spaces would appear after the newline, which is
 772  probably not what you had in mind.
 773  
 774  =head2 New "Possible precedence problem on bitwise %c operator"
 775  
 776  If you think this
 777  
 778      $x & $y == 0
 779  
 780  tests whether the bitwise AND of $x and $y is zero,
 781  you will like this warning.
 782  
 783  =head2 New "Pseudo-hashes are deprecated"
 784  
 785  This warning should have been already in 5.8.0, since they are.
 786  
 787  =head2 New "read() on %s filehandle %s"
 788  
 789  You cannot read() (or sysread()) from a closed or unopened filehandle.
 790  
 791  =head2 New "5.005 threads are deprecated"
 792  
 793  This warning should have been already in 5.8.0, since they are.
 794  
 795  =head2 New "Tied variable freed while still in use"
 796  
 797  Something pulled the plug on a live tied variable, Perl plays
 798  safe by bailing out.
 799  
 800  =head2 New "To%s: illegal mapping '%s'"
 801  
 802  An illegal user-defined Unicode casemapping was specified.
 803  
 804  =head2 New "Use of freed value in iteration"
 805  
 806  Something modified the values being iterated over.  This is not good.
 807  
 808  =head1 Changed Internals
 809  
 810  These news matter to you only if you either write XS code or like to
 811  know about or hack Perl internals (using Devel::Peek or any of the
 812  C<B::> modules counts), or like to run Perl with the C<-D> option.
 813  
 814  The embedding examples of L<perlembed> have been reviewed to be
 815  up to date and consistent: for example, the correct use of
 816  PERL_SYS_INIT3() and PERL_SYS_TERM().
 817  
 818  Extensive reworking of the pad code (the code responsible
 819  for lexical variables) has been conducted by Dave Mitchell.
 820  
 821  Extensive work on the v-strings by John Peacock.
 822  
 823  UTF-8 length and position cache: to speed up the handling of Unicode
 824  (UTF-8) scalars, a cache was introduced.  Potential problems exist if
 825  an extension bypasses the official APIs and directly modifies the PV
 826  of an SV: the UTF-8 cache does not get cleared as it should.
 827  
 828  APIs obsoleted in Perl 5.8.0, like sv_2pv, sv_catpvn, sv_catsv,
 829  sv_setsv, are again available.
 830  
 831  Certain Perl core C APIs like cxinc and regatom are no longer
 832  available at all to code outside the Perl core of the Perl core
 833  extensions.  This is intentional.  They never should have been
 834  available with the shorter names, and if you application depends on
 835  them, you should (be ashamed and) contact perl5-porters to discuss
 836  what are the proper APIs.
 837  
 838  Certain Perl core C APIs like C<Perl_list> are no longer available
 839  without their C<Perl_> prefix.  If your XS module stops working
 840  because some functions cannot be found, in many cases a simple fix is
 841  to add the C<Perl_> prefix to the function and the thread context
 842  C<aTHX_> as the first argument of the function call.  This is also how
 843  it should always have been done: letting the Perl_-less forms to leak
 844  from the core was an accident.  For cleaner embedding you can also
 845  force this for all APIs by defining at compile time the cpp define
 846  PERL_NO_SHORT_NAMES.
 847  
 848  Perl_save_bool() has been added.
 849  
 850  Regexp objects (those created with C<qr>) now have S-magic rather than
 851  R-magic.  This fixed regexps of the form /...(??{...;$x})/ to no
 852  longer ignore changes made to $x.  The S-magic avoids dropping
 853  the caching optimization and making (??{...}) constructs obscenely
 854  slow (and consequently useless).  See also L<perlguts/"Magic Variables">.
 855  Regexp::Copy was affected by this change.
 856  
 857  The Perl internal debugging macros DEBUG() and DEB() have been renamed
 858  to PERL_DEBUG() and PERL_DEB() to avoid namespace conflicts.
 859  
 860  C<-DL> removed (the leaktest had been broken and unsupported for years,
 861  use alternative debugging mallocs or tools like valgrind and Purify).
 862  
 863  Verbose modifier C<v> added for C<-DXv> and C<-Dsv>, see L<perlrun>.
 864  
 865  =head1 New Tests
 866  
 867  In Perl 5.8.0 there were about 69000 separate tests in about 700 test files,
 868  in Perl 5.8.1 there are about 77000 separate tests in about 780 test files.
 869  The exact numbers depend on the Perl configuration and on the operating
 870  system platform.
 871  
 872  =head1 Known Problems
 873  
 874  The hash randomisation mentioned in L</Incompatible Changes> is definitely
 875  problematic: it will wake dormant bugs and shake out bad assumptions.
 876  
 877  If you want to use mod_perl 2.x with Perl 5.8.1, you will need
 878  mod_perl-1.99_10 or higher.  Earlier versions of mod_perl 2.x
 879  do not work with the randomised hashes.  (mod_perl 1.x works fine.)
 880  You will also need Apache::Test 1.04 or higher.
 881  
 882  Many of the rarer platforms that worked 100% or pretty close to it
 883  with perl 5.8.0 have been left a little bit untended since their
 884  maintainers have been otherwise busy lately, and therefore there will
 885  be more failures on those platforms.  Such platforms include Mac OS
 886  Classic, IBM z/OS (and other EBCDIC platforms), and NetWare.  The most
 887  common Perl platforms (Unix and Unix-like, Microsoft platforms, and
 888  VMS) have large enough testing and expert population that they are
 889  doing well.
 890  
 891  =head2 Tied hashes in scalar context
 892  
 893  Tied hashes do not currently return anything useful in scalar context,
 894  for example when used as boolean tests:
 895  
 896      if (%tied_hash) { ... }
 897  
 898  The current nonsensical behaviour is always to return false,
 899  regardless of whether the hash is empty or has elements.
 900  
 901  The root cause is that there is no interface for the implementors of
 902  tied hashes to implement the behaviour of a hash in scalar context.
 903  
 904  =head2 Net::Ping 450_service and 510_ping_udp failures
 905  
 906  The subtests 9 and 18 of lib/Net/Ping/t/450_service.t, and the
 907  subtest 2 of lib/Net/Ping/t/510_ping_udp.t might fail if you have
 908  an unusual networking setup.  For example in the latter case the
 909  test is trying to send a UDP ping to the IP address 127.0.0.1.
 910  
 911  =head2 B::C
 912  
 913  The C-generating compiler backend B::C (the frontend being
 914  C<perlcc -c>) is even more broken than it used to be because of
 915  the extensive lexical variable changes.  (The good news is that
 916  B::Bytecode and ByteLoader are better than they used to be.)
 917  
 918  =head1 Platform Specific Problems
 919  
 920  =head2 EBCDIC Platforms
 921  
 922  IBM z/OS and other EBCDIC platforms continue to be problematic
 923  regarding Unicode support.  Many Unicode tests are skipped when
 924  they really should be fixed.
 925  
 926  =head2 Cygwin 1.5 problems
 927  
 928  In Cygwin 1.5 the F<io/tell> and F<op/sysio> tests have failures for
 929  some yet unknown reason.  In 1.5.5 the threads tests stress_cv,
 930  stress_re, and stress_string are failing unless the environment
 931  variable PERLIO is set to "perlio" (which makes also the io/tell
 932  failure go away).
 933  
 934  Perl 5.8.1 does build and work well with Cygwin 1.3: with (uname -a)
 935  C<CYGWIN_NT-5.0 ... 1.3.22(0.78/3/2) 2003-03-18 09:20 i686 ...>
 936  a 100% "make test"  was achieved with C<Configure -des -Duseithreads>.
 937  
 938  =head2 HP-UX: HP cc warnings about sendfile and sendpath
 939  
 940  With certain HP C compiler releases (e.g. B.11.11.02) you will
 941  get many warnings like this (lines wrapped for easier reading):
 942  
 943    cc: "/usr/include/sys/socket.h", line 504: warning 562:
 944      Redeclaration of "sendfile" with a different storage class specifier:
 945        "sendfile" will have internal linkage.
 946    cc: "/usr/include/sys/socket.h", line 505: warning 562:
 947      Redeclaration of "sendpath" with a different storage class specifier:
 948        "sendpath" will have internal linkage.
 949  
 950  The warnings show up both during the build of Perl and during certain
 951  lib/ExtUtils tests that invoke the C compiler.  The warning, however,
 952  is not serious and can be ignored.
 953  
 954  =head2 IRIX: t/uni/tr_7jis.t falsely failing
 955  
 956  The test t/uni/tr_7jis.t is known to report failure under 'make test'
 957  or the test harness with certain releases of IRIX (at least IRIX 6.5
 958  and MIPSpro Compilers Version 7.3.1.1m), but if run manually the test
 959  fully passes.
 960  
 961  =head2 Mac OS X: no usemymalloc
 962  
 963  The Perl malloc (C<-Dusemymalloc>) does not work at all in Mac OS X.
 964  This is not that serious, though, since the native malloc works just
 965  fine.
 966  
 967  =head2 Tru64: No threaded builds with GNU cc (gcc)
 968  
 969  In the latest Tru64 releases (e.g. v5.1B or later) gcc cannot be used
 970  to compile a threaded Perl (-Duseithreads) because the system
 971  C<< <pthread.h> >> file doesn't know about gcc.
 972  
 973  =head2 Win32: sysopen, sysread, syswrite
 974  
 975  As of the 5.8.0 release, sysopen()/sysread()/syswrite() do not behave
 976  like they used to in 5.6.1 and earlier with respect to "text" mode.
 977  These built-ins now always operate in "binary" mode (even if sysopen()
 978  was passed the O_TEXT flag, or if binmode() was used on the file
 979  handle).  Note that this issue should only make a difference for disk
 980  files, as sockets and pipes have always been in "binary" mode in the
 981  Windows port.  As this behavior is currently considered a bug,
 982  compatible behavior may be re-introduced in a future release.  Until
 983  then, the use of sysopen(), sysread() and syswrite() is not supported
 984  for "text" mode operations.
 985  
 986  =head1 Future Directions
 987  
 988  The following things B<might> happen in future.  The first publicly
 989  available releases having these characteristics will be the developer
 990  releases Perl 5.9.x, culminating in the Perl 5.10.0 release.  These
 991  are our best guesses at the moment: we reserve the right to rethink.
 992  
 993  =over 4
 994  
 995  =item *
 996  
 997  PerlIO will become The Default.  Currently (in Perl 5.8.x) the stdio
 998  library is still used if Perl thinks it can use certain tricks to
 999  make stdio go B<really> fast.  For future releases our goal is to
1000  make PerlIO go even faster.
1001  
1002  =item *
1003  
1004  A new feature called I<assertions> will be available.  This means that
1005  one can have code called assertions sprinkled in the code: usually
1006  they are optimised away, but they can be enabled with the C<-A> option.
1007  
1008  =item *
1009  
1010  A new operator C<//> (defined-or) will be available.  This means that
1011  one will be able to say
1012  
1013      $a // $b
1014  
1015  instead of
1016  
1017     defined $a ? $a : $b
1018  
1019  and
1020  
1021     $c //= $d;
1022  
1023  instead of
1024  
1025     $c = $d unless defined $c;
1026  
1027  The operator will have the same precedence and associativity as C<||>.
1028  A source code patch against the Perl 5.8.1 sources will be available
1029  in CPAN as F<authors/id/H/HM/HMBRAND/dor-5.8.1.diff>.
1030  
1031  =item *
1032  
1033  C<unpack()> will default to unpacking the C<$_>.
1034  
1035  =item *
1036  
1037  Various Copy-On-Write techniques will be investigated in hopes
1038  of speeding up Perl.
1039  
1040  =item *
1041  
1042  CPANPLUS, Inline, and Module::Build will become core modules.
1043  
1044  =item *
1045  
1046  The ability to write true lexically scoped pragmas will be introduced.
1047  
1048  =item *
1049  
1050  Work will continue on the bytecompiler and byteloader.
1051  
1052  =item *
1053  
1054  v-strings as they currently exist are scheduled to be deprecated.  The
1055  v-less form (1.2.3) will become a "version object" when used with C<use>,
1056  C<require>, and C<$VERSION>.  $^V will also be a "version object" so the
1057  printf("%vd",...) construct will no longer be needed.  The v-ful version
1058  (v1.2.3) will become obsolete.  The equivalence of strings and v-strings (e.g.
1059  that currently 5.8.0 is equal to "\5\8\0") will go away.  B<There may be no
1060  deprecation warning for v-strings>, though: it is quite hard to detect when
1061  v-strings are being used safely, and when they are not.
1062  
1063  =item *
1064  
1065  5.005 Threads Will Be Removed
1066  
1067  =item *
1068  
1069  The C<$*> Variable Will Be Removed
1070  (it was deprecated a long time ago)
1071  
1072  =item *
1073  
1074  Pseudohashes Will Be Removed
1075  
1076  =back
1077  
1078  =head1 Reporting Bugs
1079  
1080  If you find what you think is a bug, you might check the articles
1081  recently posted to the comp.lang.perl.misc newsgroup and the perl
1082  bug database at http://bugs.perl.org/ .  There may also be
1083  information at http://www.perl.com/ , the Perl Home Page.
1084  
1085  If you believe you have an unreported bug, please run the B<perlbug>
1086  program included with your release.  Be sure to trim your bug down
1087  to a tiny but sufficient test case.  Your bug report, along with the
1088  output of C<perl -V>, will be sent off to perlbug@perl.org to be
1089  analysed by the Perl porting team.  You can browse and search
1090  the Perl 5 bugs at http://bugs.perl.org/
1091  
1092  =head1 SEE ALSO
1093  
1094  The F<Changes> file for exhaustive details on what changed.
1095  
1096  The F<INSTALL> file for how to build Perl.
1097  
1098  The F<README> file for general stuff.
1099  
1100  The F<Artistic> and F<Copying> files for copyright information.
1101  
1102  =cut