3 perldelta - what's new for perl v5.7.0
7 This document describes differences between the 5.6.0 release and
10 =head1 Security Vulnerability Closed
12 A potential security vulnerability in the optional suidperl component
13 of Perl has been identified. The suidperl is neither built nor
14 installed by default. As of August the 20th, 2000, the only known
15 vulnerable platform is Linux, most likely all Linux distributions.
16 The CERT and various vendors have been alerted about the vulnerability.
18 The problem was caused by Perl trying to report a suspected security
19 exploit attempt using an external program, /bin/mail. In Linux
20 platforms the /bin/mail program had an undocumented feature which gave
21 access to a root shell, resulting in a serious compromise, instead of
22 reporting the exploit attempt. If you don't have /bin/mail or if you
23 have 'safe suid scripts' or if you haven't installed the suidperl, you
26 The exploit attempt reporting feature has been completely removed from
27 the Perl 5.7.0 release, so that particular vulnerability isn't there
28 anymore. However, further security vulnerabilities are,
29 unfortunately, always possible. The suidperl code is being reviewed
30 and if deemed too risky to continue being supported, in the extreme
31 case it may be completely removed in future releases. In any case,
32 suidperl should only be used by security experts who know exactly what
33 they are doing and why they are using suidperl instead of some other solution.
34 A good tool for similar needs is sudo: http://www.courtesan.com/sudo/
36 =head1 Incompatible Changes
38 =head2 Arrays Now Always Interpolate Into Double-Quoted Strings
40 Constructs like "foo@bar" now always assume the C<@bar> to be an array,
41 regardless of whether it is known that C<@bar> is an array.
43 =head2 bless(REF, REF) is now a fatal error
45 The semantics of bless(REF, REF) were unclear and until someone proves
46 it to make some sense, it is forbidden.
48 =head2 The eg/* Directory Removed
50 The very dusty examples in the eg/ directory have been removed.
51 Suggestions for new shiny examples welcome but the main issue is that
52 the examples need to be documented, tested, and--most importantly--maintained.
54 =head2 The lib/chat2.pl
56 The obsolete chat2 library that should never have been allowed
57 to escape the laboratory has been decommissioned.
59 =head2 Unimplemented (But Recognised) POSIX Regex Features Now Fatal
61 The unimplemented POSIX regex features [[.cc.]] and [[=c=]] are still
62 recognised but now cause fatal errors. The previous behaviour of
63 ignoring them by default and warning if requested was unacceptable
64 since it, in a way, falsely promised that the features could be used.
66 =head2 lstat(FILEHANDLE) now warns
68 lstat(FILEHANDLE) now gives a warning because the operation makes no sense.
69 In future releases this may become a fatal error.
71 =head2 Obsolete String Comparison Operators Removed
73 The long since deprecated uppercase aliases for the string comparison
74 operators (EQ, NE, LT, LE, GE, GT) have now been removed.
76 =head2 The Regular Expression Submatches Are Now Unset When Backtracking
78 The regular expression captured submatches ($1, $2, ...) are now
79 consistently unset if the match fails, instead of leaving false
80 data lying around in them.
82 =head2 tr///CU Removed, Not To Return
84 The tr///C and tr///U features have been removed and will not return;
85 the interface was a mistake. Sorry about that. For similar
86 functionality, see pack('U0', ...) and pack('C0', ...).
88 =head1 Core Enhancements
94 C<perl -d:Module=arg,arg,arg> now works (previously one couldn't pass
95 in multiple arguments.)
99 my __PACKAGE__ now works.
103 no Module; now works even if there is no "sub unimport" in the Module.
107 The numerical comparison operators return C<undef> if either operand
108 is a NaN. Previously the behaviour was unspecified.
112 C<pack('U0a*', ...)> can now be used to force a string to UTF8.
116 prototype(\&) is now available.
120 =head1 Modules and Pragmata
128 File::Temp, version 0.10, allows one to create temporary files
129 and directories in an easy, portable, and secure way.
133 The Storable extension, version 0.7.2, released the 14th of August
134 2000, has been added to the Perl distribution. Storable gives
135 persistence to Perl data structures by allowing the storage and
136 retrieval of Perl data to and from files in a fast and compact binary
141 =head2 Updated And Improved Modules and Pragmata
147 The attributes::reftype() now works on tied arguments.
151 AutoLoader can now be `stopped' by
157 B::Deparse now understands sub attributes.
161 Data::Dumper now works on negative number on 32-bit platforms where IV
162 (the Perl's integer datatype) is greater than 32 bits. Also, large
163 unsigned numbers are now dumped as such, not as large negative numbers.
167 CGI has been updated to version 2.72, released
168 the 20th of August 2000.
172 CPAN has been updated to version 1.57, released
173 the 16th of August 2000.
177 DB_File has been updated to version 1.73, released the
182 The English module can now be used without the infamous performance
185 use English '-no_performance_hit';
187 (Assuming, of course, that one doesn't need the troublesome variables
188 C<$`>, C<$&>, or C<$'>.) Also, introduce C<@LAST_MATCH_START> and
189 C<@LAST_MATCH_END> English aliases for C<@-> and C<@+>.
193 File::Find now has pre- and postprocessing callbacks.
194 It also correctly changes directories when chasing symbolic links.
195 Callbacks doing (naughtily) "next;" instead of "return;" now work.
199 File::Glob::glob() renamed to File::Glob::bsd_glob() to avoid
200 prototype mismatch with CORE::glob().
204 File::Spec has been updated to version 0.82, released the
209 Getopt::Long has been updated to version 2.23_05, released the 2nd of
214 IO::Poll has been thoroughly fixed.
218 IO::Socket::INET now works when given an unknown service name with
223 IPC::Open3 now allows the use of numeric file descriptors.
227 use lib now works identically to @INC. Removing directories
228 with 'no lib' now works.
232 Math::BigFloat now more robust (fewer "uninitialized" warnings).
236 Math::Complex now handles extreme values (e.g. cplx(1E20, 1E30)) more
241 The podlators bundle has been updated to version 1.02, released the
242 25th of April 2000. It contains the modules Pod::Man 1.04, Pod::Text
243 2.04, and modules Pod::Text::Color and Pod::Text::Termcap (no version
248 Pod::LaTeX has been updated to version 0.52, released the 15th of May
249 2000. Note that this is a complete rewrite which translates pod much
250 better, has many more options and much better documentation. It also
251 now uses the Pod::Parser backend, meaning that Pod::LaTeX will stay
252 abreast other pod translators.
256 Pod::Parser has been updated to version 1.17, released the 25th of
257 July 2000. It contains the modules Pod::Checker 1.20, Pod::Find 0.21,
258 Pod::InputObjects 1.13, Pod::ParseUtils 0.22, Pod::Parser 1.12,
259 Pod::Select 1.13, and Pod::Usage 1.13.
263 The 'debug' subpragma the 're' pragma now produces cleaner output.
267 C<%INC> now localised in a Safe compartment so that use/require work.
271 SelfLoader no longer loses C<$@> in AUTOLOAD.
275 The Shell module now has an OO interface.
279 Sys::Syslog now works on domain sockets. Also, a forked child
280 now exits correctly if it fails to open /dev/console.
284 Term::ANSIColor has been updated to version 1.03, released the 6th of
289 The Test module has been updated to version 1.14, released the 21st of June
290 1999. This is for all practical purposes identical to the previous release
291 of Test included with the Perl distribution, 1.13, but upgrading the module
292 stops the CPAN module from suggesting an upgrade.
296 Test::Harness output now prettier on failed test.
300 Text::Wrap::wtbrap now handles multiline strings properly.
304 UNIVERSAL::isa no longer caches methods incorrectly.
308 =head1 Utility Changes
310 =head2 cperl-mode version 4.31
312 The Emacs perl mode (emacs/cperl-mode.el) has been updated to version 4.31.
314 =head2 perlbc "activated"
316 The long-dormant perl bytecompiler has been added to the list of
317 installed utilities since the bytecompiler backend has been improved.
318 The bytecompiler is still very much experimental, though.
322 Perlbug is now much more robust. It also sends the bug report to perl.org,
325 =head2 perlcc now more cc-like and more robust
327 The perlcc utility has been rewritten and its user interface (that is,
328 command line) is much more like that of the UNIX C compiler, cc.
330 =head2 xsubpp now understands embedded pod
332 The xsubpp utility for extension writers now understands POD
333 documentation embedded in the *.xs files.
335 =head1 Improved Documentation
341 In many places say "alphanumeric characters" instead of "word
342 characters" because that was what was meant.
346 Eradicate "array context" from the documentation and diagnostics.
350 The return values of failing backticks (`, qx{}) are now documented
355 caller() return values now better documented.
359 SDBM_File, NDBM_File, ODBM_File, now tell about tying instead of
364 Document that the C<$(> special variable does not interpolate
365 in regular expressions.
369 The timeout unit of IO::Select is now documented to be identical
370 to the timeout unit of the 4-arg select(), that is, (optionally
371 fractional) seconds, or an undef to wait indefinitely.
375 Document the C<D> and C<d> magic types.
379 The ordering of PODs in perl.pod is now more sensible.
383 perlbook now only mentions the Camel III; all other book references
384 have been moved to perlfaq2; some good known books added.
388 Numerous missing warning/error messages added to perldiag.
392 Changed the description of perl6 in perlfaq1.
396 perlhack much extended.
404 Add perlxstut example for passing/returning refs to arrays.
408 POSIX module documentation embellished.
412 Clarified the status of shadow password support.
416 Reminded that preprocessors and source filters can alter
417 your code before Perl sees it and therefore debugging
418 can be somewhat surprising. ("I didn't write *that*!")
422 Removed incorrect documentation about implicit split to @_
423 in list context, which never really worked in Perl 5 anyway.
427 Explain that split /^/ is split /^/m.
431 Added many more sprintf() examples in perlfunc.
435 Documented the handling of negative indices to tied arrays.
439 The C<$yday> in localtime()/gmtime() is 0..364, not 1..365.
443 Documented that tr() is not tr(1): that is, do not expect regular expressions.
447 Warn about the vagaries of UDP.
451 The "uninitialized variable" warnings now say "concat or string" or
452 "join or string" instead of just "concat" or "join" since many users
453 found the "concat" a bit surprising when they were doing "just"
454 variable interpolation.
458 Documented that the values() are aliases, not copies.
462 =head2 New Documentation
468 perl56delta details the changes between the 5.005 release and the
473 perldebtut is a Perl debugging tutorial.
477 perlebcdic contains considerations for running Perl on EBCDIC platforms.
478 Note that unfortunately EBCDIC platforms that used to supported back in
479 Perl 5.005 are still unsupported by Perl 5.7.0; the plan, however, is to
480 bring them back to the fold.
484 perlnewmod tells about writing and submitting a new module.
488 perlposix-bc explains using Perl on the POSIX-BC platform
489 (a mainframe platform).
493 perlretut is a regular expression tutorial.
497 perlrequick is a regular expressions quick-start guide.
498 Yes, much quicker than perlretut.
502 perlutil explains the command line utilities packaged with the Perl
507 =head1 Performance Enhancements
509 map() that changes the size of the list should now work faster.
511 =head1 Installation and Configuration Improvements
513 =head2 INSTALL now explains 64-bit configuration.
515 In some platforms Perl can be configured to use 64-bit integers,
516 allowing 4 billion times better... sorry, switched accidentally
517 to marketdroid mode for a moment in there. (In platforms which
518 are natively 64-bit this makes no difference.)
520 =head2 Policy.sh policy change
522 If you are reusing a Policy.sh file (see INSTALL) and you use
523 Configure -Dprefix=/foo/bar and in the old Policy $prefix eq
524 $siteprefix and $prefix eq $vendorprefix, all of them will now be
525 changed to the new prefix, /foo/bar. (Previously only $prefix
526 changed.) If you do not like this new behaviour, specify prefix,
527 siteprefix, and vendorprefix explicitly.
529 =head2 Additional Library Locations
531 A new optional location for Perl libraries, otherlibdirs, is available.
532 It can be used for example for vendor add-ons without disturbing Perl's
533 own library directories.
535 =head2 gcc automatically tried if 'cc' does not seem to be working
537 In many platforms the vendor-supplied 'cc' is too stripped-down to
538 build Perl (basically, the 'cc' doesn't do ANSI C). If this seems
539 to be the case and the 'cc' does not seem to be the GNU C compiler
540 'gcc', an automatic attempt is made to find and use 'gcc' instead.
542 =head2 If gcc seems to be from a different operating system release ...
544 gcc needs to closely track the operating system release because gcc
545 wants to have its own versions of the operating system header files
546 fixed to be clean enough for gcc's tastes. Therefore using a gcc
547 compiled for a different release of the operating system is often a
548 bad idea. If Configure can find out the operating system release that
549 was used to compile the gcc and that release is different from the one
550 being used now, gcc gives a clearly visible warning that trouble may
553 =head2 If no binary compatibility with 5.005 wanted, no 5.005 modules, either
555 If no binary compatibility with the 5.005 release is wanted, Configure
556 does not suggest including the 5.005 modules in the @INC.
558 =head2 Configuration and Installation Fixes
564 Configure C<-S> can now run non-interactively
568 configure.gnu now works with options with whitespace in them
572 installperl now outputs everything to STDERR
576 $Config{byteorder} is now computed dynamically (this is more robust
577 with "fat binaries" where an executable image contains binaries for
578 more than one binary platform.)
582 =head1 Platform Specific Changes and Fixes
586 Perl now works on post-4.0 BSD/OSes.
590 Setting the C<$0> now works (as much as possible; see perlvar for details).
598 Numerous updates; currently synchronised with Cygwin 1.1.4.
604 EPOC update after Perl 5.6.0. The EPOC port home page is at
605 http://members.linuxstart.com/~oflebbe/perl/perl5.html
609 Perl now works on post-3.0 FreeBSDs.
617 Document that the C<perl -P> causes problems if one uses C<s/foo//>
618 (because the HP C compiler does funny things to that // thinking it
619 to be C++), document also the workaround.
623 C<Configure -Duse64bitall> now almost works (one failing test).
633 Numerous compilation flag and hint enhancements.
637 Accidental mixing of 32-bit and 64-bit libraries (a doomed attempt)
648 Long doubles should now work (see INSTALL).
658 Compilation of the standard Perl distribution in MacOS Classic should
659 now work--assuming you have the Metrowerks development environment and
660 the missing Mac-specific toolkit bits, contact the macperl mailing
667 MPE/iX update after Perl 5.6.0. The Perl/iX home page is at
668 http://www.bixby.org/mark/perlix.html
672 Perl now works on NetBSD/sparc.
680 Now works with usethreads (see INSTALL).
690 64-bitness using the Sun Workshop compiler now works.
694 =head2 Tru64 (aka Digital UNIX, aka DEC OSF/1)
700 Allow compiling with gcc (previously explicitly forbidden). Compiling
701 with gcc still not recommended because buggy code results, even with
706 The operating system version letter now recorded in $Config{osvers}.
716 Fixed various alignment problems that lead into core dumps either
717 during build or later.
721 no longer dying on math errors in runtime.
725 Now using full quad integers (64 bits), previously was using
726 only 46 bit integers for speed.
736 chdir() now works better despite a CRT bug.
740 Now works with MULTIPLICITY (see INSTALL).
744 Now works with Perl's malloc.
754 accept() no longer leaks memory.
758 Better chdir() return value for a non-existent directory.
762 New %ENV entries now propagate to subprocesses.
766 $ENV{LIB} now used to search for libs under Visual C.
770 A failed (pseudo)fork now returns undef and sets errno to EAGAIN.
774 Allow REG_EXPAND_SZ keys in the registry.
778 Can now send() from all threads, not just the first one.
782 Fake signal handling reenabled, bugs and all.
786 Less stack reserved per thread so that more threads can run
787 concurrently. (still 16M perl thread)
791 C<File::Spec->tmpdir()> now prefers C:/temp over /tmp
792 (works better when perl running as service).
796 Better UNC path handling under ithreads.
800 wait() and waitpid() now work much better.
804 winsock handle leak fixed.
808 =head1 Selected Bug Fixes
814 Several debugger fixes: exit code now reflects the script exit code,
815 condition C<"0"> now treated correctly, the C<d> command now checks
816 line number, the C<$.> no longer gets corrupted, all debugger output now
817 goes correctly to the socket if RemotePort is set.
821 C<*foo{FORMAT}> now works.
825 Lexical warnings now propagating correctly between scopes.
829 Line renumbering with eval and C<#line> now works.
833 Module name now mandatory after the C<-M> switch.
837 Fixed numerous memory leaks, especially in eval "".
841 Modulus of unsigned numbers now works (4063328477 % 65535 used to
842 return 27406, instead of 27047).
846 Some "not a number" warnings introduced in 5.6.0 eliminated to be
847 more compatible with 5.005. Infinity is now recognised as a number.
851 our() variables will not cause "will not stay shared" warnings
855 pack "Z" now correctly terminates the string with an "\0".
859 Fix password routines which in some shadow password platforms
860 (e.g. HP-UX) caused getpwent() to return every other entry.
864 printf() no longer resets the numeric locale to "C".
868 C<q(a\\b)> now parses correctly as C<'a\\b'>.
872 Printing quads (64-bit integers) with printf/sprintf works now
873 without q L ll prefixes (assuming you are on a quad-capable platform).
877 Regular expressions on references and overloaded scalars now work.
881 scalar() now forces scalar context even when used in void context.
885 sort() arguments are now compiled in the right wantarray context
886 (they were accidentally using the context of the sort() itself).
890 Changed the POSIX character class C<[[:space:]]> to include the (very
891 rare) vertical tabulator character. Added a new POSIX-ish character
892 class C<[[:blank:]]> which stands for horizontal whitespace (currently,
893 the space and the tabulator).
897 $AUTOLOAD, sort(), lock(), and spawning subprocesses
898 in multiple thread simultaneously are now thread-safe.
902 Allow read-only string on left hand side of non-modifying tr///.
906 Several Unicode fixes (but still not perfect).
908 BOMs (byte order marks) in the beginning of Perl files
909 (scripts, modules) should now be transparently skipped.
910 UTF16 encoded Perl files should now be read correctly.
912 The character tables have been updated to new Unicode 3.0 features.
914 chr() for values greater than 127 now create utf8 when under use
917 Comparing with utf8 data does not magically upgrade non-utf8 data into
920 C<IsAlnum>, C<IsAlpha>, and C<IsWord> now match titlecase.
922 Concatenation with the C<.> operator or via variable interpolation,
923 C<eq>, C<substr>, C<reverse>, C<quotemeta>, the C<x> operator,
924 substitution with C<s///>, single-quoted UTF8, should now work--in
927 The C<tr///> operator now works I<slightly> better but is still rather
928 broken. Note that the C<tr///CU> functionality has been removed (but
929 see pack('U0', ...)).
931 Zero entries were missing from the Unicode classes like C<IsDigit>.
935 =head1 New or Changed Diagnostics
937 All regular expression compilation error messages are now hopefully
938 easier to understand both because the error message now comes before
939 the failed regex and because the point of failure is now clearly
942 The various "opened only for", "on closed", "never opened" warnings
943 drop the C<main::> prefix for filehandles in the C<main> package,
944 for example C<STDIN> instead of <main::STDIN>.
950 (perhaps you forgot to load "%s"?)
952 (F) This is an educated guess made in conjunction with the message
953 "Can't locate object method \"%s\" via package \"%s\"". It often means
954 that a method requires a package that has not been loaded.
958 Ambiguous range in transliteration operator
960 (F) You wrote something like C<tr/a-z-0//> which doesn't mean anything at
961 all. To include a C<-> character in a transliteration, put it either
962 first or last. (In the past, C<tr/a-z-0//> was synonymous with
963 C<tr/a-y//>, which was probably not what you would have expected.)
967 The "Unrecognized escape" warning has been extended to include C<\8>,
968 C<\9>, and C<\_>. There is no need to escape any of the C<\w> characters.
972 =head1 Changed Internals
976 perlapi.pod (a companion to perlguts) now attempts to document the
981 There is now a way to build a really minimal perl called microperl.
982 Building microperl does not require even running Configure;
983 C<make -f Makefile.micro> should be enough. Beware: microperl makes
984 many assumptions, some of which may be too bold; the resulting
985 executable may crash or otherwise misbehave in wondrous ways. For
986 careful hackers only.
988 =head2 Publicise More Functions
990 Added rsignal(), whichsig(), do_join() to the publicised API.
992 =head2 Propagating Exception Objects via Perl_croak() IN XS code
994 Made possible to propagate customised exceptions via croak()ing.
996 =head2 UTF8 Interfaces
998 Added is_utf8_char(), is_utf8_string(), bytes_to_utf8(), and utf8_to_bytes().
1000 =head2 xsub attributes
1002 Now xsubs can have attributes just like subs.
1004 =head1 Known Problems
1006 =head2 Unicode Support Still Far From Perfect
1008 We're working on it. Stay tuned.
1010 =head2 EBCDIC Still A Lost Platform
1012 The plan is to bring them back.
1014 =head2 Building Extensions Can Fail Because Of Largefiles
1016 Certain extensions like mod_perl and BSD::Resource are known to have
1017 issues with `largefiles', a change brought by Perl 5.6.0 in where file
1018 offsets are by default 64 bits wide (assuming the platform supports
1019 such large files). Modules may fail to compile at all or compile and
1020 work incorrectly. Currently there is no good solution for the problem
1021 but Configure now stores the flags and libraries that affect the
1022 largefileness to the %Config hash, the extensions that are having
1023 problems can try configuring themselves without the largefileness.
1024 This is admittedly not a clean solution.
1026 =head1 Obsolete Diagnostics
1030 =item In string, @%s now must be written as \@%s
1032 (F) It used to be that Perl would try to guess whether you wanted an
1033 array interpolated or a literal @. It did this when the string was
1034 first used at runtime. Now strings are parsed at compile time, and
1035 ambiguous instances of @ must be disambiguated, either by prepending a
1036 backslash to indicate a literal, or by declaring (or using) the array
1037 within the program before the string (lexically). (I<Someday it will
1038 simply assume that an unbackslashed @ interpolates an array.>)
1042 That day has arrived.
1044 =head1 Reporting Bugs
1046 If you find what you think is a bug, you might check the articles
1047 recently posted to the comp.lang.perl.misc newsgroup and the perl
1048 bug database at http://bugs.perl.org. There may also be
1049 information at http://www.perl.com/perl/, the Perl Home Page.
1051 If you believe you have an unreported bug, please run the B<perlbug>
1052 program included with your release. Be sure to trim your bug down
1053 to a tiny but sufficient test case. Your bug report, along with the
1054 output of C<perl -V>, will be sent off to perlbug@perl.org to be
1055 analysed by the Perl porting team.
1059 The F<Changes> file for exhaustive details on what changed.
1061 The F<INSTALL> file for how to build Perl.
1063 The F<README> file for general stuff.
1065 The F<Artistic> and F<Copying> files for copyright information.
1069 Written by Jarkko Hietaniemi <F<jhi@iki.fi>>, with many contributions
1070 from The Perl Porters and Perl Users submitting feedback and patches.
1072 Send omissions or corrections to <F<perlbug@perl.org>>.