1PERL561DELTA(1) Perl Programmers Reference Guide PERL561DELTA(1)
2
6 perl561delta - what's new for perl v5.6.x
7
9 This document describes differences between the 5.005 release and the
10 5.6.1 release.
11
13 This section contains a summary of the changes between the 5.6.0
14 release and the 5.6.1 release. More details about the changes men‐
15 tioned here may be found in the Changes files that accompany the Perl
16 source distribution. See perlhack for pointers to online resources
17 where you can inspect the individual patches described by these
18 changes.
19 Security Issues
21 suidperl will not run /bin/mail anymore, because some platforms have a
23 /bin/mail that is vulnerable to buffer overflow attacks.
24 Note that suidperl is neither built nor installed by default in any
26 recent version of perl. Use of suidperl is highly discouraged. If you
27 think you need it, try alternatives such as sudo first. See
28 http://www.courtesan.com/sudo/ .
29 Core bug fixes
31 This is not an exhaustive list. It is intended to cover only the sig‐
33 nificant user-visible changes.
34 "UNIVERSAL::isa()"
36 A bug in the caching mechanism used by "UNIVERSAL::isa()" that
37 affected base.pm has been fixed. The bug has existed since the
38 5.005 releases, but wasn't tickled by base.pm in those releases.
39 Memory leaks
41 Various cases of memory leaks and attempts to access uninitialized
42 memory have been cured. See "Known Problems" below for further
43 issues.
44 Numeric conversions
46 Numeric conversions did not recognize changes in the string value
47 properly in certain circumstances.
48 In other situations, large unsigned numbers (those above 2**31)
50 could sometimes lose their unsignedness, causing bogus results in
51 arithmetic operations.
52 Integer modulus on large unsigned integers sometimes returned
54 incorrect values.
55 Perl 5.6.0 generated "not a number" warnings on certain conversions
57 where previous versions didn't.
58 These problems have all been rectified.
60 Infinity is now recognized as a number.
62 qw(a\\b)
64 In Perl 5.6.0, qw(a\\b) produced a string with two backslashes
65 instead of one, in a departure from the behavior in previous ver‐
66 sions. The older behavior has been reinstated.
67 caller()
69 caller() could cause core dumps in certain situations. Carp was
70 sometimes affected by this problem.
71 Bugs in regular expressions
73 Pattern matches on overloaded values are now handled correctly.
74 Perl 5.6.0 parsed m/\x{ab}/ incorrectly, leading to spurious warn‐
76 ings. This has been corrected.
77 The RE engine found in Perl 5.6.0 accidentally pessimised certain
79 kinds of simple pattern matches. These are now handled better.
80 Regular expression debug output (whether through "use re 'debug'"
82 or via "-Dr") now looks better.
83 Multi-line matches like ""a\nxb\n" =~ /(?!\A)x/m" were flawed. The
85 bug has been fixed.
86 Use of $& could trigger a core dump under some situations. This is
88 now avoided.
89 Match variables $1 et al., weren't being unset when a pattern match
91 was backtracking, and the anomaly showed up inside "/...(?{ ...
92 }).../" etc. These variables are now tracked correctly.
93 pos() did not return the correct value within s///ge in earlier
95 versions. This is now handled correctly.
96 "slurp" mode
98 readline() on files opened in "slurp" mode could return an extra ""
99 at the end in certain situations. This has been corrected.
100 Autovivification of symbolic references to special variables
102 Autovivification of symbolic references of special variables
103 described in perlvar (as in "${$num}") was accidentally disabled.
104 This works again now.
105 Lexical warnings
107 Lexical warnings now propagate correctly into "eval "..."".
108 "use warnings qw(FATAL all)" did not work as intended. This has
110 been corrected.
111 Lexical warnings could leak into other scopes in some situations.
113 This is now fixed.
114 warnings::enabled() now reports the state of $^W correctly if the
116 caller isn't using lexical warnings.
117 Spurious warnings and errors
119 Perl 5.6.0 could emit spurious warnings about redefinition of
120 dl_error() when statically building extensions into perl. This has
121 been corrected.
122 "our" variables could result in bogus "Variable will not stay
124 shared" warnings. This is now fixed.
125 "our" variables of the same name declared in two sibling blocks
127 resulted in bogus warnings about "redeclaration" of the variables.
128 The problem has been corrected.
129 glob()
131 Compatibility of the builtin glob() with old csh-based glob has
132 been improved with the addition of GLOB_ALPHASORT option. See
133 "File::Glob".
134 File::Glob::glob() has been renamed to File::Glob::bsd_glob()
136 because the name clashes with the builtin glob(). The older name
137 is still available for compatibility, but is deprecated.
138 Spurious syntax errors generated in certain situations, when glob()
140 caused File::Glob to be loaded for the first time, have been fixed.
141 Tainting
143 Some cases of inconsistent taint propagation (such as within hash
144 values) have been fixed.
145 The tainting behavior of sprintf() has been rationalized. It does
147 not taint the result of floating point formats anymore, making the
148 behavior consistent with that of string interpolation.
149 sort()
151 Arguments to sort() weren't being provided the right wantarray()
152 context. The comparison block is now run in scalar context, and
153 the arguments to be sorted are always provided list context.
154 sort() is also fully reentrant, in the sense that the sort function
156 can itself call sort(). This did not work reliably in previous
157 releases.
158 #line directives
160 #line directives now work correctly when they appear at the very
161 beginning of "eval "..."".
162 Subroutine prototypes
164 The (\&) prototype now works properly.
165 map()
167 map() could get pathologically slow when the result list it gener‐
168 ates is larger than the source list. The performance has been
169 improved for common scenarios.
170 Debugger
172 Debugger exit code now reflects the script exit code.
173 Condition "0" in breakpoints is now treated correctly.
175 The "d" command now checks the line number.
177 $. is no longer corrupted by the debugger.
179 All debugger output now correctly goes to the socket if RemotePort
181 is set.
182 PERL5OPT
184 PERL5OPT can be set to more than one switch group. Previously, it
185 used to be limited to one group of options only.
186 chop()
188 chop(@list) in list context returned the characters chopped in
189 reverse order. This has been reversed to be in the right order.
190 Unicode support
192 Unicode support has seen a large number of incremental improve‐
193 ments, but continues to be highly experimental. It is not expected
194 to be fully supported in the 5.6.x maintenance releases.
195 substr(), join(), repeat(), reverse(), quotemeta() and string con‐
197 catenation were all handling Unicode strings incorrectly in Perl
198 5.6.0. This has been corrected.
199 Support for "tr///CU" and "tr///UC" etc., have been removed since
201 we realized the interface is broken. For similar functionality,
202 see "pack" in perlfunc.
203 The Unicode Character Database has been updated to version 3.0.1
205 with additions made available to the public as of August 30, 2000.
206 The Unicode character classes \p{Blank} and \p{SpacePerl} have been
208 added. "Blank" is like C isblank(), that is, it contains only
209 "horizontal whitespace" (the space character is, the newline
210 isn't), and the "SpacePerl" is the Unicode equivalent of "\s"
211 (\p{Space} isn't, since that includes the vertical tabulator char‐
212 acter, whereas "\s" doesn't.)
213 If you are experimenting with Unicode support in perl, the develop‐
215 ment versions of Perl may have more to offer. In particular, I/O
216 layers are now available in the development track, but not in the
217 maintenance track, primarily to do backward compatibility issues.
218 Unicode support is also evolving rapidly on a daily basis in the
219 development track--the maintenance track only reflects the most
220 conservative of these changes.
221 64-bit support
223 Support for 64-bit platforms has been improved, but continues to be
224 experimental. The level of support varies greatly among platforms.
225 Compiler
227 The B Compiler and its various backends have had many incremental
228 improvements, but they continue to remain highly experimental. Use
229 in production environments is discouraged.
230 The perlcc tool has been rewritten so that the user interface is
232 much more like that of a C compiler.
233 The perlbc tools has been removed. Use "perlcc -B" instead.
235 Lvalue subroutines
237 There have been various bugfixes to support lvalue subroutines bet‐
238 ter. However, the feature still remains experimental.
239 IO::Socket
241 IO::Socket::INET failed to open the specified port if the service
242 name was not known. It now correctly uses the supplied port number
243 as is.
244 File::Find
246 File::Find now chdir()s correctly when chasing symbolic links.
247 xsubpp
249 xsubpp now tolerates embedded POD sections.
250 "no Module;"
252 "no Module;" does not produce an error even if Module does not have
253 an unimport() method. This parallels the behavior of "use" vis-a-
254 vis "import".
255 Tests
257 A large number of tests have been added.
258 Core features
260 untie() will now call an UNTIE() hook if it exists. See perltie for
262 details.
263 The "-DT" command line switch outputs copious tokenizing information.
265 See perlrun.
266 Arrays are now always interpolated in double-quotish strings. Previ‐
268 ously, "foo@bar.com" used to be a fatal error at compile time, if an
269 array @bar was not used or declared. This transitional behavior was
270 intended to help migrate perl4 code, and is deemed to be no longer use‐
271 ful. See "Arrays now always interpolate into double-quoted strings".
272 keys(), each(), pop(), push(), shift(), splice() and unshift() can all
274 be overridden now.
275 "my __PACKAGE__ $obj" now does the expected thing.
277 Configuration issues
279 On some systems (IRIX and Solaris among them) the system malloc is
281 demonstrably better. While the defaults haven't been changed in order
282 to retain binary compatibility with earlier releases, you may be better
283 off building perl with "Configure -Uusemymalloc ..." as discussed in
284 the INSTALL file.
285 "Configure" has been enhanced in various ways:
287 · Minimizes use of temporary files.
289 · By default, does not link perl with libraries not used by it, such
291 as the various dbm libraries. SunOS 4.x hints preserve behavior on
292 that platform.
293 · Support for pdp11-style memory models has been removed due to obso‐
295 lescence.
296 · Building outside the source tree is supported on systems that have
298 symbolic links. This is done by running
299 sh /path/to/source/Configure -Dmksymlinks ...
301 make all test install
302 in a directory other than the perl source directory. See INSTALL.
304 · "Configure -S" can be run non-interactively.
306 Documentation
308 README.aix, README.solaris and README.macos have been added.
310 README.posix-bc has been renamed to README.bs2000. These are installed
311 as perlaix, perlsolaris, perlmacos, and perlbs2000 respectively.
312 The following pod documents are brand new:
314 perlclib Internal replacements for standard C library functions
316 perldebtut Perl debugging tutorial
317 perlebcdic Considerations for running Perl on EBCDIC platforms
318 perlnewmod Perl modules: preparing a new module for distribution
319 perlrequick Perl regular expressions quick start
320 perlretut Perl regular expressions tutorial
321 perlutil utilities packaged with the Perl distribution
322 The INSTALL file has been expanded to cover various issues, such as
324 64-bit support.
325 A longer list of contributors has been added to the source distribu‐
327 tion. See the file "AUTHORS".
328 Numerous other changes have been made to the included documentation and
330 FAQs.
331 Bundled modules
333 The following modules have been added.
335 B::Concise
337 Walks Perl syntax tree, printing concise info about ops. See
338 B::Concise.
339 File::Temp
341 Returns name and handle of a temporary file safely. See
342 File::Temp.
343 Pod::LaTeX
345 Converts Pod data to formatted LaTeX. See Pod::LaTeX.
346 Pod::Text::Overstrike
348 Converts POD data to formatted overstrike text. See
349 Pod::Text::Overstrike.
350 The following modules have been upgraded.
352 CGI CGI v2.752 is now included.
354 CPAN
356 CPAN v1.59_54 is now included.
357 Class::Struct
359 Various bugfixes have been added.
360 DB_File
362 DB_File v1.75 supports newer Berkeley DB versions, among other
363 improvements.
364 Devel::Peek
366 Devel::Peek has been enhanced to support dumping of memory statis‐
367 tics, when perl is built with the included malloc().
368 File::Find
370 File::Find now supports pre and post-processing of the files in
371 order to sort() them, etc.
372 Getopt::Long
374 Getopt::Long v2.25 is included.
375 IO::Poll
377 Various bug fixes have been included.
378 IPC::Open3
380 IPC::Open3 allows use of numeric file descriptors.
381 Math::BigFloat
383 The fmod() function supports modulus operations. Various bug fixes
384 have also been included.
385 Math::Complex
387 Math::Complex handles inf, NaN etc., better.
388 Net::Ping
390 ping() could fail on odd number of data bytes, and when the echo
391 service isn't running. This has been corrected.
392 Opcode
394 A memory leak has been fixed.
395 Pod::Parser
397 Version 1.13 of the Pod::Parser suite is included.
398 Pod::Text
400 Pod::Text and related modules have been upgraded to the versions in
401 podlators suite v2.08.
402 SDBM_File
404 On dosish platforms, some keys went missing because of lack of sup‐
405 port for files with "holes". A workaround for the problem has been
406 added.
407 Sys::Syslog
409 Various bug fixes have been included.
410 Tie::RefHash
412 Now supports Tie::RefHash::Nestable to automagically tie hashref
413 values.
414 Tie::SubstrHash
416 Various bug fixes have been included.
417 Platform-specific improvements
419 The following new ports are now available.
421 NCR MP-RAS
423 NonStop-UX
424 Perl now builds under Amdahl UTS.
426 Perl has also been verified to build under Amiga OS.
428 Support for EPOC has been much improved. See README.epoc.
430 Building perl with -Duseithreads or -Duse5005threads now works under
432 HP-UX 10.20 (previously it only worked under 10.30 or later). You will
433 need a thread library package installed. See README.hpux.
434 Long doubles should now work under Linux.
436 Mac OS Classic is now supported in the mainstream source package. See
438 README.macos.
439 Support for MPE/iX has been updated. See README.mpeix.
441 Support for OS/2 has been improved. See "os2/Changes" and README.os2.
443 Dynamic loading on z/OS (formerly OS/390) has been improved. See
445 README.os390.
446 Support for VMS has seen many incremental improvements, including bet‐
448 ter support for operators like backticks and system(), and better %ENV
449 handling. See "README.vms" and perlvms.
450 Support for Stratus VOS has been improved. See "vos/Changes" and
452 README.vos.
453 Support for Windows has been improved.
455 · fork() emulation has been improved in various ways, but still con‐
457 tinues to be experimental. See perlfork for known bugs and
458 caveats.
459 · %SIG has been enabled under USE_ITHREADS, but its use is completely
461 unsupported under all configurations.
462 · Borland C++ v5.5 is now a supported compiler that can build Perl.
464 However, the generated binaries continue to be incompatible with
465 those generated by the other supported compilers (GCC and Visual
466 C++).
467 · Non-blocking waits for child processes (or pseudo-processes) are
469 supported via "waitpid($pid, &POSIX::WNOHANG)".
470 · A memory leak in accept() has been fixed.
472 · wait(), waitpid() and backticks now return the correct exit status
474 under Windows 9x.
475 · Trailing new %ENV entries weren't propagated to child processes.
477 This is now fixed.
478 · Current directory entries in %ENV are now correctly propagated to
480 child processes.
481 · Duping socket handles with open(F, ">&MYSOCK") now works under Win‐
483 dows 9x.
484 · The makefiles now provide a single switch to bulk-enable all the
486 features enabled in ActiveState ActivePerl (a popular binary dis‐
487 tribution).
488 · Win32::GetCwd() correctly returns C:\ instead of C: when at the
490 drive root. Other bugs in chdir() and Cwd::cwd() have also been
491 fixed.
492 · fork() correctly returns undef and sets EAGAIN when it runs out of
494 pseudo-process handles.
495 · ExtUtils::MakeMaker now uses $ENV{LIB} to search for libraries.
497 · UNC path handling is better when perl is built to support fork().
499 · A handle leak in socket handling has been fixed.
501 · send() works from within a pseudo-process.
503 Unless specifically qualified otherwise, the remainder of this document
505 covers changes between the 5.005 and 5.6.0 releases.
506
508 Interpreter cloning, threads, and concurrency
509 Perl 5.6.0 introduces the beginnings of support for running multiple
511 interpreters concurrently in different threads. In conjunction with
512 the perl_clone() API call, which can be used to selectively duplicate
513 the state of any given interpreter, it is possible to compile a piece
514 of code once in an interpreter, clone that interpreter one or more
515 times, and run all the resulting interpreters in distinct threads.
516 On the Windows platform, this feature is used to emulate fork() at the
518 interpreter level. See perlfork for details about that.
519 This feature is still in evolution. It is eventually meant to be used
521 to selectively clone a subroutine and data reachable from that subrou‐
522 tine in a separate interpreter and run the cloned subroutine in a sepa‐
523 rate thread. Since there is no shared data between the interpreters,
524 little or no locking will be needed (unless parts of the symbol table
525 are explicitly shared). This is obviously intended to be an easy-to-
526 use replacement for the existing threads support.
527 Support for cloning interpreters and interpreter concurrency can be
529 enabled using the -Dusethreads Configure option (see win32/Makefile for
530 how to enable it on Windows.) The resulting perl executable will be
531 functionally identical to one that was built with -Dmultiplicity, but
532 the perl_clone() API call will only be available in the former.
533 -Dusethreads enables the cpp macro USE_ITHREADS by default, which in
535 turn enables Perl source code changes that provide a clear separation
536 between the op tree and the data it operates with. The former is
537 immutable, and can therefore be shared between an interpreter and all
538 of its clones, while the latter is considered local to each inter‐
539 preter, and is therefore copied for each clone.
540 Note that building Perl with the -Dusemultiplicity Configure option is
542 adequate if you wish to run multiple independent interpreters concur‐
543 rently in different threads. -Dusethreads only provides the additional
544 functionality of the perl_clone() API call and other support for run‐
545 ning cloned interpreters concurrently.
546 NOTE: This is an experimental feature. Implementation details are
548 subject to change.
549 Lexically scoped warning categories
551 You can now control the granularity of warnings emitted by perl at a
553 finer level using the "use warnings" pragma. warnings and perllexwarn
554 have copious documentation on this feature.
555 Unicode and UTF-8 support
557 Perl now uses UTF-8 as its internal representation for character
559 strings. The "utf8" and "bytes" pragmas are used to control this sup‐
560 port in the current lexical scope. See perlunicode, utf8 and bytes for
561 more information.
562 This feature is expected to evolve quickly to support some form of I/O
564 disciplines that can be used to specify the kind of input and output
565 data (bytes or characters). Until that happens, additional modules
566 from CPAN will be needed to complete the toolkit for dealing with Uni‐
567 code.
568 NOTE: This should be considered an experimental feature. Implementation
570 details are subject to change.
571 Support for interpolating named characters
573 The new "\N" escape interpolates named characters within strings. For
575 example, "Hi! \N{WHITE SMILING FACE}" evaluates to a string with a Uni‐
576 code smiley face at the end.
577 "our" declarations
579 An "our" declaration introduces a value that can be best understood as
581 a lexically scoped symbolic alias to a global variable in the package
582 that was current where the variable was declared. This is mostly use‐
583 ful as an alternative to the "vars" pragma, but also provides the
584 opportunity to introduce typing and other attributes for such vari‐
585 ables. See "our" in perlfunc.
586 Support for strings represented as a vector of ordinals
588 Literals of the form "v1.2.3.4" are now parsed as a string composed of
590 characters with the specified ordinals. This is an alternative, more
591 readable way to construct (possibly Unicode) strings instead of inter‐
592 polating characters, as in "\x{1}\x{2}\x{3}\x{4}". The leading "v" may
593 be omitted if there are more than two ordinals, so 1.2.3 is parsed the
594 same as "v1.2.3".
595 Strings written in this form are also useful to represent version "num‐
597 bers". It is easy to compare such version "numbers" (which are really
598 just plain strings) using any of the usual string comparison operators
599 "eq", "ne", "lt", "gt", etc., or perform bitwise string operations on
600 them using "⎪", "&", etc.
601 In conjunction with the new $^V magic variable (which contains the perl
603 version as a string), such literals can be used as a readable way to
604 check if you're running a particular version of Perl:
605 # this will parse in older versions of Perl also
607 if ($^V and $^V gt v5.6.0) {
608 # new features supported
609 }
610 "require" and "use" also have some special magic to support such liter‐
612 als. They will be interpreted as a version rather than as a module
613 name:
614 require v5.6.0; # croak if $^V lt v5.6.0
616 use v5.6.0; # same, but croaks at compile-time
617 Alternatively, the "v" may be omitted if there is more than one dot:
619 require 5.6.0;
621 use 5.6.0;
622 Also, "sprintf" and "printf" support the Perl-specific format flag %v
624 to print ordinals of characters in arbitrary strings:
625 printf "v%vd", $^V; # prints current version, such as "v5.5.650"
627 printf "%*vX", ":", $addr; # formats IPv6 address
628 printf "%*vb", " ", $bits; # displays bitstring
629 See "Scalar value constructors" in perldata for additional information.
631 Improved Perl version numbering system
633 Beginning with Perl version 5.6.0, the version number convention has
635 been changed to a "dotted integer" scheme that is more commonly found
636 in open source projects.
637 Maintenance versions of v5.6.0 will be released as v5.6.1, v5.6.2 etc.
639 The next development series following v5.6.0 will be numbered v5.7.x,
640 beginning with v5.7.0, and the next major production release following
641 v5.6.0 will be v5.8.0.
642 The English module now sets $PERL_VERSION to $^V (a string value)
644 rather than $] (a numeric value). (This is a potential incompatibil‐
645 ity. Send us a report via perlbug if you are affected by this.)
646 The v1.2.3 syntax is also now legal in Perl. See "Support for strings
648 represented as a vector of ordinals" for more on that.
649 To cope with the new versioning system's use of at least three signifi‐
651 cant digits for each version component, the method used for increment‐
652 ing the subversion number has also changed slightly. We assume that
653 versions older than v5.6.0 have been incrementing the subversion compo‐
654 nent in multiples of 10. Versions after v5.6.0 will increment them by
655 1. Thus, using the new notation, 5.005_03 is the "same" as v5.5.30,
656 and the first maintenance version following v5.6.0 will be v5.6.1
657 (which should be read as being equivalent to a floating point value of
658 5.006_001 in the older format, stored in $]).
659 New syntax for declaring subroutine attributes
661 Formerly, if you wanted to mark a subroutine as being a method call or
663 as requiring an automatic lock() when it is entered, you had to declare
664 that with a "use attrs" pragma in the body of the subroutine. That can
665 now be accomplished with declaration syntax, like this:
666 sub mymethod : locked method;
668 ...
669 sub mymethod : locked method {
670 ...
671 }
672 sub othermethod :locked :method;
674 ...
675 sub othermethod :locked :method {
676 ...
677 }
678 (Note how only the first ":" is mandatory, and whitespace surrounding
680 the ":" is optional.)
681 AutoSplit.pm and SelfLoader.pm have been updated to keep the attributes
683 with the stubs they provide. See attributes.
684 File and directory handles can be autovivified
686 Similar to how constructs such as "$x->[0]" autovivify a reference,
688 handle constructors (open(), opendir(), pipe(), socketpair(),
689 sysopen(), socket(), and accept()) now autovivify a file or directory
690 handle if the handle passed to them is an uninitialized scalar vari‐
691 able. This allows the constructs such as "open(my $fh, ...)" and
692 "open(local $fh,...)" to be used to create filehandles that will con‐
693 veniently be closed automatically when the scope ends, provided there
694 are no other references to them. This largely eliminates the need for
695 typeglobs when opening filehandles that must be passed around, as in
696 the following example:
697 sub myopen {
699 open my $fh, "@_"
700 or die "Can't open '@_': $!";
701 return $fh;
702 }
703 {
705 my $f = myopen("</etc/motd");
706 print <$f>;
707 # $f implicitly closed here
708 }
709 open() with more than two arguments
711 If open() is passed three arguments instead of two, the second argument
713 is used as the mode and the third argument is taken to be the file
714 name. This is primarily useful for protecting against unintended magic
715 behavior of the traditional two-argument form. See "open" in perlfunc.
716 64-bit support
718 Any platform that has 64-bit integers either
720 (1) natively as longs or ints
722 (2) via special compiler flags
723 (3) using long long or int64_t
724 is able to use "quads" (64-bit integers) as follows:
726 · constants (decimal, hexadecimal, octal, binary) in the code
728 · arguments to oct() and hex()
730 · arguments to print(), printf() and sprintf() (flag prefixes ll, L,
732 q)
733 · printed as such
735 · pack() and unpack() "q" and "Q" formats
737 · in basic arithmetics: + - * / % (NOTE: operating close to the lim‐
739 its of the integer values may produce surprising results)
740 · in bit arithmetics: & ⎪ ^ ~ << >> (NOTE: these used to be forced to
742 be 32 bits wide but now operate on the full native width.)
743 · vec()
745 Note that unless you have the case (a) you will have to configure and
747 compile Perl using the -Duse64bitint Configure flag.
748 NOTE: The Configure flags -Duselonglong and -Duse64bits have been
750 deprecated. Use -Duse64bitint instead.
751 There are actually two modes of 64-bitness: the first one is achieved
753 using Configure -Duse64bitint and the second one using Configure
754 -Duse64bitall. The difference is that the first one is minimal and the
755 second one maximal. The first works in more places than the second.
756 The "use64bitint" does only as much as is required to get 64-bit inte‐
758 gers into Perl (this may mean, for example, using "long longs") while
759 your memory may still be limited to 2 gigabytes (because your pointers
760 could still be 32-bit). Note that the name "64bitint" does not imply
761 that your C compiler will be using 64-bit "int"s (it might, but it
762 doesn't have to): the "use64bitint" means that you will be able to have
763 64 bits wide scalar values.
764 The "use64bitall" goes all the way by attempting to switch also inte‐
766 gers (if it can), longs (and pointers) to being 64-bit. This may cre‐
767 ate an even more binary incompatible Perl than -Duse64bitint: the
768 resulting executable may not run at all in a 32-bit box, or you may
769 have to reboot/reconfigure/rebuild your operating system to be 64-bit
770 aware.
771 Natively 64-bit systems like Alpha and Cray need neither -Duse64bitint
773 nor -Duse64bitall.
774 Last but not least: note that due to Perl's habit of always using
776 floating point numbers, the quads are still not true integers. When
777 quads overflow their limits (0...18_446_744_073_709_551_615 unsigned,
778 -9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they
779 are silently promoted to floating point numbers, after which they will
780 start losing precision (in their lower digits).
781 NOTE: 64-bit support is still experimental on most platforms.
783 Existing support only covers the LP64 data model. In particular, the
784 LLP64 data model is not yet supported. 64-bit libraries and system
785 APIs on many platforms have not stabilized--your mileage may vary.
786 Large file support
788 If you have filesystems that support "large files" (files larger than 2
790 gigabytes), you may now also be able to create and access them from
791 Perl.
792 NOTE: The default action is to enable large file support, if
794 available on the platform.
795 If the large file support is on, and you have a Fcntl constant O_LARGE‐
797 FILE, the O_LARGEFILE is automatically added to the flags of sysopen().
798 Beware that unless your filesystem also supports "sparse files" seeking
800 to umpteen petabytes may be inadvisable.
801 Note that in addition to requiring a proper file system to do large
803 files you may also need to adjust your per-process (or your per-system,
804 or per-process-group, or per-user-group) maximum filesize limits before
805 running Perl scripts that try to handle large files, especially if you
806 intend to write such files.
807 Finally, in addition to your process/process group maximum filesize
809 limits, you may have quota limits on your filesystems that stop you
810 (your user id or your user group id) from using large files.
811 Adjusting your process/user/group/file system/operating system limits
813 is outside the scope of Perl core language. For process limits, you
814 may try increasing the limits using your shell's limits/limit/ulimit
815 command before running Perl. The BSD::Resource extension (not included
816 with the standard Perl distribution) may also be of use, it offers the
817 getrlimit/setrlimit interface that can be used to adjust process
818 resource usage limits, including the maximum filesize limit.
819 Long doubles
821 In some systems you may be able to use long doubles to enhance the
823 range and precision of your double precision floating point numbers
824 (that is, Perl's numbers). Use Configure -Duselongdouble to enable
825 this support (if it is available).
826 "more bits"
828 You can "Configure -Dusemorebits" to turn on both the 64-bit support
830 and the long double support.
831 Enhanced support for sort() subroutines
833 Perl subroutines with a prototype of "($$)", and XSUBs in general, can
835 now be used as sort subroutines. In either case, the two elements to
836 be compared are passed as normal parameters in @_. See "sort" in perl‐
837 func.
838 For unprototyped sort subroutines, the historical behavior of passing
840 the elements to be compared as the global variables $a and $b remains
841 unchanged.
842 "sort $coderef @foo" allowed
844 sort() did not accept a subroutine reference as the comparison function
846 in earlier versions. This is now permitted.
847 File globbing implemented internally
849 Perl now uses the File::Glob implementation of the glob() operator
851 automatically. This avoids using an external csh process and the prob‐
852 lems associated with it.
853 NOTE: This is currently an experimental feature. Interfaces and
855 implementation are subject to change.
856 Support for CHECK blocks
858 In addition to "BEGIN", "INIT", "END", "DESTROY" and "AUTOLOAD", sub‐
860 routines named "CHECK" are now special. These are queued up during
861 compilation and behave similar to END blocks, except they are called at
862 the end of compilation rather than at the end of execution. They can‐
863 not be called directly.
864 POSIX character class syntax [: :] supported
866 For example to match alphabetic characters use /[[:alpha:]]/. See
868 perlre for details.
869 Better pseudo-random number generator
871 In 5.005_0x and earlier, perl's rand() function used the C library
873 rand(3) function. As of 5.005_52, Configure tests for drand48(), ran‐
874 dom(), and rand() (in that order) and picks the first one it finds.
875 These changes should result in better random numbers from rand().
877 Improved "qw//" operator
879 The "qw//" operator is now evaluated at compile time into a true list
881 instead of being replaced with a run time call to "split()". This
882 removes the confusing misbehaviour of "qw//" in scalar context, which
883 had inherited that behaviour from split().
884 Thus:
886 $foo = ($bar) = qw(a b c); print "$foo⎪$bar\n";
888 now correctly prints "3⎪a", instead of "2⎪a".
890 Better worst-case behavior of hashes
892 Small changes in the hashing algorithm have been implemented in order
894 to improve the distribution of lower order bits in the hashed value.
895 This is expected to yield better performance on keys that are repeated
896 sequences.
897 pack() format 'Z' supported
899 The new format type 'Z' is useful for packing and unpacking null-termi‐
901 nated strings. See "pack" in perlfunc.
902 pack() format modifier '!' supported
904 The new format type modifier '!' is useful for packing and unpacking
906 native shorts, ints, and longs. See "pack" in perlfunc.
907 pack() and unpack() support counted strings
909 The template character '/' can be used to specify a counted string type
911 to be packed or unpacked. See "pack" in perlfunc.
912 Comments in pack() templates
914 The '#' character in a template introduces a comment up to end of the
916 line. This facilitates documentation of pack() templates.
917 Weak references
919 In previous versions of Perl, you couldn't cache objects so as to allow
921 them to be deleted if the last reference from outside the cache is
922 deleted. The reference in the cache would hold a reference count on
923 the object and the objects would never be destroyed.
924 Another familiar problem is with circular references. When an object
926 references itself, its reference count would never go down to zero, and
927 it would not get destroyed until the program is about to exit.
928 Weak references solve this by allowing you to "weaken" any reference,
930 that is, make it not count towards the reference count. When the last
931 non-weak reference to an object is deleted, the object is destroyed and
932 all the weak references to the object are automatically undef-ed.
933 To use this feature, you need the Devel::WeakRef package from CPAN,
935 which contains additional documentation.
936 NOTE: This is an experimental feature. Details are subject to change.
938 Binary numbers supported
940 Binary numbers are now supported as literals, in s?printf formats, and
942 "oct()":
943 $answer = 0b101010;
945 printf "The answer is: %b\n", oct("0b101010");
946 Lvalue subroutines
948 Subroutines can now return modifiable lvalues. See "Lvalue subrou‐
950 tines" in perlsub.
951 NOTE: This is an experimental feature. Details are subject to change.
953 Some arrows may be omitted in calls through references
955 Perl now allows the arrow to be omitted in many constructs involving
957 subroutine calls through references. For example, "$foo[10]->('foo')"
958 may now be written "$foo[10]('foo')". This is rather similar to how
959 the arrow may be omitted from "$foo[10]->{'foo'}". Note however, that
960 the arrow is still required for "foo(10)->('bar')".
961 Boolean assignment operators are legal lvalues
963 Constructs such as "($a ⎪⎪= 2) += 1" are now allowed.
965 exists() is supported on subroutine names
967 The exists() builtin now works on subroutine names. A subroutine is
969 considered to exist if it has been declared (even if implicitly). See
970 "exists" in perlfunc for examples.
971 exists() and delete() are supported on array elements
973 The exists() and delete() builtins now work on simple arrays as well.
975 The behavior is similar to that on hash elements.
976 exists() can be used to check whether an array element has been ini‐
978 tialized. This avoids autovivifying array elements that don't exist.
979 If the array is tied, the EXISTS() method in the corresponding tied
980 package will be invoked.
981 delete() may be used to remove an element from the array and return it.
983 The array element at that position returns to its uninitialized state,
984 so that testing for the same element with exists() will return false.
985 If the element happens to be the one at the end, the size of the array
986 also shrinks up to the highest element that tests true for exists(), or
987 0 if none such is found. If the array is tied, the DELETE() method in
988 the corresponding tied package will be invoked.
989 See "exists" in perlfunc and "delete" in perlfunc for examples.
991 Pseudo-hashes work better
993 Dereferencing some types of reference values in a pseudo-hash, such as
995 "$ph->{foo}[1]", was accidentally disallowed. This has been corrected.
996 When applied to a pseudo-hash element, exists() now reports whether the
998 specified value exists, not merely if the key is valid.
999 delete() now works on pseudo-hashes. When given a pseudo-hash element
1001 or slice it deletes the values corresponding to the keys (but not the
1002 keys themselves). See "Pseudo-hashes: Using an array as a hash" in
1003 perlref.
1004 Pseudo-hash slices with constant keys are now optimized to array
1006 lookups at compile-time.
1007 List assignments to pseudo-hash slices are now supported.
1009 The "fields" pragma now provides ways to create pseudo-hashes, via
1011 fields::new() and fields::phash(). See fields.
1012 NOTE: The pseudo-hash data type continues to be experimental.
1014 Limiting oneself to the interface elements provided by the
1015 fields pragma will provide protection from any future changes.
1016 Automatic flushing of output buffers
1018 fork(), exec(), system(), qx//, and pipe open()s now flush buffers of
1020 all files opened for output when the operation was attempted. This
1021 mostly eliminates confusing buffering mishaps suffered by users unaware
1022 of how Perl internally handles I/O.
1023 This is not supported on some platforms like Solaris where a suitably
1025 correct implementation of fflush(NULL) isn't available.
1026 Better diagnostics on meaningless filehandle operations
1028 Constructs such as "open(<FH>)" and "close(<FH>)" are compile time
1030 errors. Attempting to read from filehandles that were opened only for
1031 writing will now produce warnings (just as writing to read-only file‐
1032 handles does).
1033 Where possible, buffered data discarded from duped input filehandle
1035 "open(NEW, "<&OLD")" now attempts to discard any data that was previ‐
1037 ously read and buffered in "OLD" before duping the handle. On plat‐
1038 forms where doing this is allowed, the next read operation on "NEW"
1039 will return the same data as the corresponding operation on "OLD".
1040 Formerly, it would have returned the data from the start of the follow‐
1041 ing disk block instead.
1042 eof() has the same old magic as <>
1044 "eof()" would return true if no attempt to read from "<>" had yet been
1046 made. "eof()" has been changed to have a little magic of its own, it
1047 now opens the "<>" files.
1048 binmode() can be used to set :crlf and :raw modes
1050 binmode() now accepts a second argument that specifies a discipline for
1052 the handle in question. The two pseudo-disciplines ":raw" and ":crlf"
1053 are currently supported on DOS-derivative platforms. See "binmode" in
1054 perlfunc and open.
1055 "-T" filetest recognizes UTF-8 encoded files as "text"
1057 The algorithm used for the "-T" filetest has been enhanced to correctly
1059 identify UTF-8 content as "text".
1060 system(), backticks and pipe open now reflect exec() failure
1062 On Unix and similar platforms, system(), qx() and open(FOO, "cmd ⎪")
1064 etc., are implemented via fork() and exec(). When the underlying
1065 exec() fails, earlier versions did not report the error properly, since
1066 the exec() happened to be in a different process.
1067 The child process now communicates with the parent about the error in
1069 launching the external command, which allows these constructs to return
1070 with their usual error value and set $!.
1071 Improved diagnostics
1073 Line numbers are no longer suppressed (under most likely circumstances)
1075 during the global destruction phase.
1076 Diagnostics emitted from code running in threads other than the main
1078 thread are now accompanied by the thread ID.
1079 Embedded null characters in diagnostics now actually show up. They
1081 used to truncate the message in prior versions.
1082 $foo::a and $foo::b are now exempt from "possible typo" warnings only
1084 if sort() is encountered in package "foo".
1085 Unrecognized alphabetic escapes encountered when parsing quote con‐
1087 structs now generate a warning, since they may take on new semantics in
1088 later versions of Perl.
1089 Many diagnostics now report the internal operation in which the warning
1091 was provoked, like so:
1092 Use of uninitialized value in concatenation (.) at (eval 1) line 1.
1094 Use of uninitialized value in print at (eval 1) line 1.
1095 Diagnostics that occur within eval may also report the file and line
1097 number where the eval is located, in addition to the eval sequence num‐
1098 ber and the line number within the evaluated text itself. For example:
1099 Not enough arguments for scalar at (eval 4)[newlib/perl5db.pl:1411] line 2, at EOF
1101 Diagnostics follow STDERR
1103 Diagnostic output now goes to whichever file the "STDERR" handle is
1105 pointing at, instead of always going to the underlying C runtime
1106 library's "stderr".
1107 More consistent close-on-exec behavior
1109 On systems that support a close-on-exec flag on filehandles, the flag
1111 is now set for any handles created by pipe(), socketpair(), socket(),
1112 and accept(), if that is warranted by the value of $^F that may be in
1113 effect. Earlier versions neglected to set the flag for handles created
1114 with these operators. See "pipe" in perlfunc, "socketpair" in perl‐
1115 func, "socket" in perlfunc, "accept" in perlfunc, and "$^F" in perlvar.
1116 syswrite() ease-of-use
1118 The length argument of "syswrite()" has become optional.
1120 Better syntax checks on parenthesized unary operators
1122 Expressions such as:
1124 print defined(&foo,&bar,&baz);
1126 print uc("foo","bar","baz");
1127 undef($foo,&bar);
1128 used to be accidentally allowed in earlier versions, and produced
1130 unpredictable behaviour. Some produced ancillary warnings when used in
1131 this way; others silently did the wrong thing.
1132 The parenthesized forms of most unary operators that expect a single
1134 argument now ensure that they are not called with more than one argu‐
1135 ment, making the cases shown above syntax errors. The usual behaviour
1136 of:
1137 print defined &foo, &bar, &baz;
1139 print uc "foo", "bar", "baz";
1140 undef $foo, &bar;
1141 remains unchanged. See perlop.
1143 Bit operators support full native integer width
1145 The bit operators (& ⎪ ^ ~ << >>) now operate on the full native inte‐
1147 gral width (the exact size of which is available in $Config{ivsize}).
1148 For example, if your platform is either natively 64-bit or if Perl has
1149 been configured to use 64-bit integers, these operations apply to 8
1150 bytes (as opposed to 4 bytes on 32-bit platforms). For portability, be
1151 sure to mask off the excess bits in the result of unary "~", e.g., "~$x
1152 & 0xffffffff".
1153 Improved security features
1155 More potentially unsafe operations taint their results for improved
1157 security.
1158 The "passwd" and "shell" fields returned by the getpwent(), getpwnam(),
1160 and getpwuid() are now tainted, because the user can affect their own
1161 encrypted password and login shell.
1162 The variable modified by shmread(), and messages returned by msgrcv()
1164 (and its object-oriented interface IPC::SysV::Msg::rcv) are also
1165 tainted, because other untrusted processes can modify messages and
1166 shared memory segments for their own nefarious purposes.
1167 More functional bareword prototype (*)
1169 Bareword prototypes have been rationalized to enable them to be used to
1171 override builtins that accept barewords and interpret them in a special
1172 way, such as "require" or "do".
1173 Arguments prototyped as "*" will now be visible within the subroutine
1175 as either a simple scalar or as a reference to a typeglob. See "Proto‐
1176 types" in perlsub.
1177 "require" and "do" may be overridden
1179 "require" and "do 'file'" operations may be overridden locally by
1181 importing subroutines of the same name into the current package (or
1182 globally by importing them into the CORE::GLOBAL:: namespace). Over‐
1183 riding "require" will also affect "use", provided the override is visi‐
1184 ble at compile-time. See "Overriding Built-in Functions" in perlsub.
1185 $^X variables may now have names longer than one character
1187 Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax
1189 error. Now variable names that begin with a control character may be
1190 arbitrarily long. However, for compatibility reasons, these variables
1191 must be written with explicit braces, as "${^XY}" for example.
1192 "${^XYZ}" is synonymous with ${"\cXYZ"}. Variable names with more than
1193 one control character, such as "${^XY^Z}", are illegal.
1194 The old syntax has not changed. As before, `^X' may be either a lit‐
1196 eral control-X character or the two-character sequence `caret' plus
1197 `X'. When braces are omitted, the variable name stops after the con‐
1198 trol character. Thus "$^XYZ" continues to be synonymous with "$^X .
1199 "YZ"" as before.
1200 As before, lexical variables may not have names beginning with control
1202 characters. As before, variables whose names begin with a control
1203 character are always forced to be in package `main'. All such vari‐
1204 ables are reserved for future extensions, except those that begin with
1205 "^_", which may be used by user programs and are guaranteed not to
1206 acquire special meaning in any future version of Perl.
1207 New variable $^C reflects "-c" switch
1209 $^C has a boolean value that reflects whether perl is being run in com‐
1211 pile-only mode (i.e. via the "-c" switch). Since BEGIN blocks are exe‐
1212 cuted under such conditions, this variable enables perl code to deter‐
1213 mine whether actions that make sense only during normal running are
1214 warranted. See perlvar.
1215 New variable $^V contains Perl version as a string
1217 $^V contains the Perl version number as a string composed of characters
1219 whose ordinals match the version numbers, i.e. v5.6.0. This may be
1220 used in string comparisons.
1221 See "Support for strings represented as a vector of ordinals" for an
1223 example.
1224 Optional Y2K warnings
1226 If Perl is built with the cpp macro "PERL_Y2KWARN" defined, it emits
1228 optional warnings when concatenating the number 19 with another number.
1229 This behavior must be specifically enabled when running Configure. See
1231 INSTALL and README.Y2K.
1232 Arrays now always interpolate into double-quoted strings
1234 In double-quoted strings, arrays now interpolate, no matter what. The
1236 behavior in earlier versions of perl 5 was that arrays would interpo‐
1237 late into strings if the array had been mentioned before the string was
1238 compiled, and otherwise Perl would raise a fatal compile-time error.
1239 In versions 5.000 through 5.003, the error was
1240 Literal @example now requires backslash
1242 In versions 5.004_01 through 5.6.0, the error was
1244 In string, @example now must be written as \@example
1246 The idea here was to get people into the habit of writing "fred\@exam‐
1248 ple.com" when they wanted a literal "@" sign, just as they have always
1249 written "Give me back my \$5" when they wanted a literal "$" sign.
1250 Starting with 5.6.1, when Perl now sees an "@" sign in a double-quoted
1252 string, it always attempts to interpolate an array, regardless of
1253 whether or not the array has been used or declared already. The fatal
1254 error has been downgraded to an optional warning:
1255 Possible unintended interpolation of @example in string
1257 This warns you that "fred@example.com" is going to turn into "fred.com"
1259 if you don't backslash the "@". See
1260 http://www.plover.com/~mjd/perl/at-error.html for more details about
1261 the history here.
1262 @- and @+ provide starting/ending offsets of regex submatches
1264 The new magic variables @- and @+ provide the starting and ending off‐
1266 sets, respectively, of $&, $1, $2, etc. See perlvar for details.
1267
1269 Modules
1270 attributes
1272 While used internally by Perl as a pragma, this module also pro‐
1273 vides a way to fetch subroutine and variable attributes. See
1274 attributes.
1275 B The Perl Compiler suite has been extensively reworked for this
1277 release. More of the standard Perl testsuite passes when run under
1278 the Compiler, but there is still a significant way to go to achieve
1279 production quality compiled executables.
1280 NOTE: The Compiler suite remains highly experimental. The
1282 generated code may not be correct, even when it manages to execute
1283 without errors.
1284 Benchmark
1286 Overall, Benchmark results exhibit lower average error and better
1287 timing accuracy.
1288 You can now run tests for n seconds instead of guessing the right
1290 number of tests to run: e.g., timethese(-5, ...) will run each code
1291 for at least 5 CPU seconds. Zero as the "number of repetitions"
1292 means "for at least 3 CPU seconds". The output format has also
1293 changed. For example:
1294 use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
1296 will now output something like this:
1298 Benchmark: running a, b, each for at least 5 CPU seconds...
1300 a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
1301 b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
1302 New features: "each for at least N CPU seconds...", "wallclock
1304 secs", and the "@ operations/CPU second (n=operations)".
1305 timethese() now returns a reference to a hash of Benchmark objects
1307 containing the test results, keyed on the names of the tests.
1308 timethis() now returns the iterations field in the Benchmark result
1310 object instead of 0.
1311 timethese(), timethis(), and the new cmpthese() (see below) can
1313 also take a format specifier of 'none' to suppress output.
1314 A new function countit() is just like timeit() except that it takes
1316 a TIME instead of a COUNT.
1317 A new function cmpthese() prints a chart comparing the results of
1319 each test returned from a timethese() call. For each possible pair
1320 of tests, the percentage speed difference (iters/sec or sec‐
1321 onds/iter) is shown.
1322 For other details, see Benchmark.
1324 ByteLoader
1326 The ByteLoader is a dedicated extension to generate and run Perl
1327 bytecode. See ByteLoader.
1328 constant
1330 References can now be used.
1331 The new version also allows a leading underscore in constant names,
1333 but disallows a double leading underscore (as in "__LINE__"). Some
1334 other names are disallowed or warned against, including BEGIN, END,
1335 etc. Some names which were forced into main:: used to fail
1336 silently in some cases; now they're fatal (outside of main::) and
1337 an optional warning (inside of main::). The ability to detect
1338 whether a constant had been set with a given name has been added.
1339 See constant.
1341 charnames
1343 This pragma implements the "\N" string escape. See charnames.
1344 Data::Dumper
1346 A "Maxdepth" setting can be specified to avoid venturing too deeply
1347 into deep data structures. See Data::Dumper.
1348 The XSUB implementation of Dump() is now automatically called if
1350 the "Useqq" setting is not in use.
1351 Dumping "qr//" objects works correctly.
1353 DB "DB" is an experimental module that exposes a clean abstraction to
1355 Perl's debugging API.
1356 DB_File
1358 DB_File can now be built with Berkeley DB versions 1, 2 or 3. See
1359 "ext/DB_File/Changes".
1360 Devel::DProf
1362 Devel::DProf, a Perl source code profiler has been added. See
1363 Devel::DProf and dprofpp.
1364 Devel::Peek
1366 The Devel::Peek module provides access to the internal representa‐
1367 tion of Perl variables and data. It is a data debugging tool for
1368 the XS programmer.
1369 Dumpvalue
1371 The Dumpvalue module provides screen dumps of Perl data.
1372 DynaLoader
1374 DynaLoader now supports a dl_unload_file() function on platforms
1375 that support unloading shared objects using dlclose().
1376 Perl can also optionally arrange to unload all extension shared
1378 objects loaded by Perl. To enable this, build Perl with the Con‐
1379 figure option "-Accflags=-DDL_UNLOAD_ALL_AT_EXIT". (This maybe
1380 useful if you are using Apache with mod_perl.)
1381 English
1383 $PERL_VERSION now stands for $^V (a string value) rather than for
1384 $] (a numeric value).
1385 Env Env now supports accessing environment variables like PATH as array
1387 variables.
1388 Fcntl
1390 More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for
1391 large file (more than 4GB) access (NOTE: the O_LARGEFILE is auto‐
1392 matically added to sysopen() flags if large file support has been
1393 configured, as is the default), Free/Net/OpenBSD locking behaviour
1394 flags F_FLOCK, F_POSIX, Linux F_SHLCK, and O_ACCMODE: the combined
1395 mask of O_RDONLY, O_WRONLY, and O_RDWR. The seek()/sysseek() con‐
1396 stants SEEK_SET, SEEK_CUR, and SEEK_END are available via the
1397 ":seek" tag. The chmod()/stat() S_IF* constants and S_IS* func‐
1398 tions are available via the ":mode" tag.
1399 File::Compare
1401 A compare_text() function has been added, which allows custom com‐
1402 parison functions. See File::Compare.
1403 File::Find
1405 File::Find now works correctly when the wanted() function is either
1406 autoloaded or is a symbolic reference.
1407 A bug that caused File::Find to lose track of the working directory
1409 when pruning top-level directories has been fixed.
1410 File::Find now also supports several other options to control its
1412 behavior. It can follow symbolic links if the "follow" option is
1413 specified. Enabling the "no_chdir" option will make File::Find
1414 skip changing the current directory when walking directories. The
1415 "untaint" flag can be useful when running with taint checks
1416 enabled.
1417 See File::Find.
1419 File::Glob
1421 This extension implements BSD-style file globbing. By default, it
1422 will also be used for the internal implementation of the glob()
1423 operator. See File::Glob.
1424 File::Spec
1426 New methods have been added to the File::Spec module: devnull()
1427 returns the name of the null device (/dev/null on Unix) and
1428 tmpdir() the name of the temp directory (normally /tmp on Unix).
1429 There are now also methods to convert between absolute and relative
1430 filenames: abs2rel() and rel2abs(). For compatibility with operat‐
1431 ing systems that specify volume names in file paths, the split‐
1432 path(), splitdir(), and catdir() methods have been added.
1433 File::Spec::Functions
1435 The new File::Spec::Functions modules provides a function interface
1436 to the File::Spec module. Allows shorthand
1437 $fullname = catfile($dir1, $dir2, $file);
1439 instead of
1441 $fullname = File::Spec->catfile($dir1, $dir2, $file);
1443 Getopt::Long
1445 Getopt::Long licensing has changed to allow the Perl Artistic
1446 License as well as the GPL. It used to be GPL only, which got in
1447 the way of non-GPL applications that wanted to use Getopt::Long.
1448 Getopt::Long encourages the use of Pod::Usage to produce help mes‐
1450 sages. For example:
1451 use Getopt::Long;
1453 use Pod::Usage;
1454 my $man = 0;
1455 my $help = 0;
1456 GetOptions('help⎪?' => \$help, man => \$man) or pod2usage(2);
1457 pod2usage(1) if $help;
1458 pod2usage(-exitstatus => 0, -verbose => 2) if $man;
1459 __END__
1461 =head1 NAME
1463 sample - Using Getopt::Long and Pod::Usage
1465 =head1 SYNOPSIS
1467 sample [options] [file ...]
1469 Options:
1471 -help brief help message
1472 -man full documentation
1473 =head1 OPTIONS
1475 =over 8
1477 =item B<-help>
1479 Print a brief help message and exits.
1481 =item B<-man>
1483 Prints the manual page and exits.
1485 =back
1487 =head1 DESCRIPTION
1489 B<This program> will read the given input file(s) and do something
1491 useful with the contents thereof.
1492 =cut
1494 See Pod::Usage for details.
1496 A bug that prevented the non-option call-back <> from being speci‐
1498 fied as the first argument has been fixed.
1499 To specify the characters < and > as option starters, use ><. Note,
1501 however, that changing option starters is strongly deprecated.
1502 IO write() and syswrite() will now accept a single-argument form of
1504 the call, for consistency with Perl's syswrite().
1505 You can now create a TCP-based IO::Socket::INET without forcing a
1507 connect attempt. This allows you to configure its options (like
1508 making it non-blocking) and then call connect() manually.
1509 A bug that prevented the IO::Socket::protocol() accessor from ever
1511 returning the correct value has been corrected.
1512 IO::Socket::connect now uses non-blocking IO instead of alarm() to
1514 do connect timeouts.
1515 IO::Socket::accept now uses select() instead of alarm() for doing
1517 timeouts.
1518 IO::Socket::INET->new now sets $! correctly on failure. $@ is still
1520 set for backwards compatibility.
1521 JPL Java Perl Lingo is now distributed with Perl. See jpl/README for
1523 more information.
1524 lib "use lib" now weeds out any trailing duplicate entries. "no lib"
1526 removes all named entries.
1527 Math::BigInt
1529 The bitwise operations "<<", ">>", "&", "⎪", and "~" are now sup‐
1530 ported on bigints.
1531 Math::Complex
1533 The accessor methods Re, Im, arg, abs, rho, and theta can now also
1534 act as mutators (accessor $z->Re(), mutator $z->Re(3)).
1535 The class method "display_format" and the corresponding object
1537 method "display_format", in addition to accepting just one argu‐
1538 ment, now can also accept a parameter hash. Recognized keys of a
1539 parameter hash are "style", which corresponds to the old one param‐
1540 eter case, and two new parameters: "format", which is a
1541 printf()-style format string (defaults usually to "%.15g", you can
1542 revert to the default by setting the format string to "undef") used
1543 for both parts of a complex number, and "polar_pretty_print"
1544 (defaults to true), which controls whether an attempt is made to
1545 try to recognize small multiples and rationals of pi (2pi, pi/2) at
1546 the argument (angle) of a polar complex number.
1547 The potentially disruptive change is that in list context both
1549 methods now return the parameter hash, instead of only the value of
1550 the "style" parameter.
1551 Math::Trig
1553 A little bit of radial trigonometry (cylindrical and spherical),
1554 radial coordinate conversions, and the great circle distance were
1555 added.
1556 Pod::Parser, Pod::InputObjects
1558 Pod::Parser is a base class for parsing and selecting sections of
1559 pod documentation from an input stream. This module takes care of
1560 identifying pod paragraphs and commands in the input and hands off
1561 the parsed paragraphs and commands to user-defined methods which
1562 are free to interpret or translate them as they see fit.
1563 Pod::InputObjects defines some input objects needed by Pod::Parser,
1565 and for advanced users of Pod::Parser that need more about a com‐
1566 mand besides its name and text.
1567 As of release 5.6.0 of Perl, Pod::Parser is now the officially
1569 sanctioned "base parser code" recommended for use by all pod2xxx
1570 translators. Pod::Text (pod2text) and Pod::Man (pod2man) have
1571 already been converted to use Pod::Parser and efforts to convert
1572 Pod::HTML (pod2html) are already underway. For any questions or
1573 comments about pod parsing and translating issues and utilities,
1574 please use the pod-people@perl.org mailing list.
1575 For further information, please see Pod::Parser and Pod::InputOb‐
1577 jects.
1578 Pod::Checker, podchecker
1580 This utility checks pod files for correct syntax, according to
1581 perlpod. Obvious errors are flagged as such, while warnings are
1582 printed for mistakes that can be handled gracefully. The checklist
1583 is not complete yet. See Pod::Checker.
1584 Pod::ParseUtils, Pod::Find
1586 These modules provide a set of gizmos that are useful mainly for
1587 pod translators. Pod::Find traverses directory structures and
1588 returns found pod files, along with their canonical names (like
1589 "File::Spec::Unix"). Pod::ParseUtils contains Pod::List (useful
1590 for storing pod list information), Pod::Hyperlink (for parsing the
1591 contents of "L<>" sequences) and Pod::Cache (for caching informa‐
1592 tion about pod files, e.g., link nodes).
1593 Pod::Select, podselect
1595 Pod::Select is a subclass of Pod::Parser which provides a function
1596 named "podselect()" to filter out user-specified sections of raw
1597 pod documentation from an input stream. podselect is a script that
1598 provides access to Pod::Select from other scripts to be used as a
1599 filter. See Pod::Select.
1600 Pod::Usage, pod2usage
1602 Pod::Usage provides the function "pod2usage()" to print usage mes‐
1603 sages for a Perl script based on its embedded pod documentation.
1604 The pod2usage() function is generally useful to all script authors
1605 since it lets them write and maintain a single source (the pods)
1606 for documentation, thus removing the need to create and maintain
1607 redundant usage message text consisting of information already in
1608 the pods.
1609 There is also a pod2usage script which can be used from other kinds
1611 of scripts to print usage messages from pods (even for non-Perl
1612 scripts with pods embedded in comments).
1613 For details and examples, please see Pod::Usage.
1615 Pod::Text and Pod::Man
1617 Pod::Text has been rewritten to use Pod::Parser. While pod2text()
1618 is still available for backwards compatibility, the module now has
1619 a new preferred interface. See Pod::Text for the details. The new
1620 Pod::Text module is easily subclassed for tweaks to the output, and
1621 two such subclasses (Pod::Text::Termcap for man-page-style bold and
1622 underlining using termcap information, and Pod::Text::Color for
1623 markup with ANSI color sequences) are now standard.
1624 pod2man has been turned into a module, Pod::Man, which also uses
1626 Pod::Parser. In the process, several outstanding bugs related to
1627 quotes in section headers, quoting of code escapes, and nested
1628 lists have been fixed. pod2man is now a wrapper script around this
1629 module.
1630 SDBM_File
1632 An EXISTS method has been added to this module (and sdbm_exists()
1633 has been added to the underlying sdbm library), so one can now call
1634 exists on an SDBM_File tied hash and get the correct result, rather
1635 than a runtime error.
1636 A bug that may have caused data loss when more than one disk block
1638 happens to be read from the database in a single FETCH() has been
1639 fixed.
1640 Sys::Syslog
1642 Sys::Syslog now uses XSUBs to access facilities from syslog.h so it
1643 no longer requires syslog.ph to exist.
1644 Sys::Hostname
1646 Sys::Hostname now uses XSUBs to call the C library's gethostname()
1647 or uname() if they exist.
1648 Term::ANSIColor
1650 Term::ANSIColor is a very simple module to provide easy and read‐
1651 able access to the ANSI color and highlighting escape sequences,
1652 supported by most ANSI terminal emulators. It is now included
1653 standard.
1654 Time::Local
1656 The timelocal() and timegm() functions used to silently return
1657 bogus results when the date fell outside the machine's integer
1658 range. They now consistently croak() if the date falls in an
1659 unsupported range.
1660 Win32
1662 The error return value in list context has been changed for all
1663 functions that return a list of values. Previously these functions
1664 returned a list with a single element "undef" if an error occurred.
1665 Now these functions return the empty list in these situations.
1666 This applies to the following functions:
1667 Win32::FsType
1669 Win32::GetOSVersion
1670 The remaining functions are unchanged and continue to return
1672 "undef" on error even in list context.
1673 The Win32::SetLastError(ERROR) function has been added as a comple‐
1675 ment to the Win32::GetLastError() function.
1676 The new Win32::GetFullPathName(FILENAME) returns the full absolute
1678 pathname for FILENAME in scalar context. In list context it
1679 returns a two-element list containing the fully qualified directory
1680 name and the filename. See Win32.
1681 XSLoader
1683 The XSLoader extension is a simpler alternative to DynaLoader. See
1684 XSLoader.
1685 DBM Filters
1687 A new feature called "DBM Filters" has been added to all the DBM
1688 modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File.
1689 DBM Filters add four new methods to each DBM module:
1690 filter_store_key
1692 filter_store_value
1693 filter_fetch_key
1694 filter_fetch_value
1695 These can be used to filter key-value pairs before the pairs are
1697 written to the database or just after they are read from the data‐
1698 base. See perldbmfilter for further information.
1699 Pragmata
1701 "use attrs" is now obsolete, and is only provided for backward-compati‐
1703 bility. It's been replaced by the "sub : attributes" syntax. See
1704 "Subroutine Attributes" in perlsub and attributes.
1705 Lexical warnings pragma, "use warnings;", to control optional warnings.
1707 See perllexwarn.
1708 "use filetest" to control the behaviour of filetests ("-r" "-w" ...).
1710 Currently only one subpragma implemented, "use filetest 'access';",
1711 that uses access(2) or equivalent to check permissions instead of using
1712 stat(2) as usual. This matters in filesystems where there are ACLs
1713 (access control lists): the stat(2) might lie, but access(2) knows bet‐
1714 ter.
1715 The "open" pragma can be used to specify default disciplines for handle
1717 constructors (e.g. open()) and for qx//. The two pseudo-disciplines
1718 ":raw" and ":crlf" are currently supported on DOS-derivative platforms
1719 (i.e. where binmode is not a no-op). See also "binmode() can be used
1720 to set :crlf and :raw modes".
1721
1723 dprofpp
1724 "dprofpp" is used to display profile data generated using
1726 "Devel::DProf". See dprofpp.
1727 find2perl
1729 The "find2perl" utility now uses the enhanced features of the
1731 File::Find module. The -depth and -follow options are supported. Pod
1732 documentation is also included in the script.
1733 h2xs
1735 The "h2xs" tool can now work in conjunction with "C::Scan" (available
1737 from CPAN) to automatically parse real-life header files. The "-M",
1738 "-a", "-k", and "-o" options are new.
1739 perlcc
1741 "perlcc" now supports the C and Bytecode backends. By default, it gen‐
1743 erates output from the simple C backend rather than the optimized C
1744 backend.
1745 Support for non-Unix platforms has been improved.
1747 perldoc
1749 "perldoc" has been reworked to avoid possible security holes. It will
1751 not by default let itself be run as the superuser, but you may still
1752 use the -U switch to try to make it drop privileges first.
1753 The Perl Debugger
1755 Many bug fixes and enhancements were added to perl5db.pl, the Perl
1757 debugger. The help documentation was rearranged. New commands include
1758 "< ?", "> ?", and "{ ?" to list out current actions, "man docpage" to
1759 run your doc viewer on some perl docset, and support for quoted
1760 options. The help information was rearranged, and should be viewable
1761 once again if you're using less as your pager. A serious security hole
1762 was plugged--you should immediately remove all older versions of the
1763 Perl debugger as installed in previous releases, all the way back to
1764 perl3, from your system to avoid being bitten by this.
1765
1767 Many of the platform-specific README files are now part of the perl
1768 installation. See perl for the complete list.
1769 perlapi.pod
1771 The official list of public Perl API functions.
1772 perlboot.pod
1774 A tutorial for beginners on object-oriented Perl.
1775 perlcompile.pod
1777 An introduction to using the Perl Compiler suite.
1778 perldbmfilter.pod
1780 A howto document on using the DBM filter facility.
1781 perldebug.pod
1783 All material unrelated to running the Perl debugger, plus all low-
1784 level guts-like details that risked crushing the casual user of the
1785 debugger, have been relocated from the old manpage to the next
1786 entry below.
1787 perldebguts.pod
1789 This new manpage contains excessively low-level material not
1790 related to the Perl debugger, but slightly related to debugging
1791 Perl itself. It also contains some arcane internal details of how
1792 the debugging process works that may only be of interest to devel‐
1793 opers of Perl debuggers.
1794 perlfork.pod
1796 Notes on the fork() emulation currently available for the Windows
1797 platform.
1798 perlfilter.pod
1800 An introduction to writing Perl source filters.
1801 perlhack.pod
1803 Some guidelines for hacking the Perl source code.
1804 perlintern.pod
1806 A list of internal functions in the Perl source code. (List is
1807 currently empty.)
1808 perllexwarn.pod
1810 Introduction and reference information about lexically scoped warn‐
1811 ing categories.
1812 perlnumber.pod
1814 Detailed information about numbers as they are represented in Perl.
1815 perlopentut.pod
1817 A tutorial on using open() effectively.
1818 perlreftut.pod
1820 A tutorial that introduces the essentials of references.
1821 perltootc.pod
1823 A tutorial on managing class data for object modules.
1824 perltodo.pod
1826 Discussion of the most often wanted features that may someday be
1827 supported in Perl.
1828 perlunicode.pod
1830 An introduction to Unicode support features in Perl.
1831
1833 Simple sort() using { $a <=> $b } and the like are optimized
1834 Many common sort() operations using a simple inlined block are now
1836 optimized for faster performance.
1837 Optimized assignments to lexical variables
1839 Certain operations in the RHS of assignment statements have been opti‐
1841 mized to directly set the lexical variable on the LHS, eliminating
1842 redundant copying overheads.
1843 Faster subroutine calls
1845 Minor changes in how subroutine calls are handled internally provide
1847 marginal improvements in performance.
1848 delete(), each(), values() and hash iteration are faster
1850 The hash values returned by delete(), each(), values() and hashes in a
1852 list context are the actual values in the hash, instead of copies.
1853 This results in significantly better performance, because it eliminates
1854 needless copying in most situations.
1855
1857 -Dusethreads means something different
1858 The -Dusethreads flag now enables the experimental interpreter-based
1860 thread support by default. To get the flavor of experimental threads
1861 that was in 5.005 instead, you need to run Configure with "-Dusethreads
1862 -Duse5005threads".
1863 As of v5.6.0, interpreter-threads support is still lacking a way to
1865 create new threads from Perl (i.e., "use Thread;" will not work with
1866 interpreter threads). "use Thread;" continues to be available when you
1867 specify the -Duse5005threads option to Configure, bugs and all.
1868 NOTE: Support for threads continues to be an experimental feature.
1870 Interfaces and implementation are subject to sudden and drastic changes.
1871 New Configure flags
1873 The following new flags may be enabled on the Configure command line by
1875 running Configure with "-Dflag".
1876 usemultiplicity
1878 usethreads useithreads (new interpreter threads: no Perl API yet)
1879 usethreads use5005threads (threads as they were in 5.005)
1880 use64bitint (equal to now deprecated 'use64bits')
1882 use64bitall
1883 uselongdouble
1885 usemorebits
1886 uselargefiles
1887 usesocks (only SOCKS v5 supported)
1888 Threadedness and 64-bitness now more daring
1890 The Configure options enabling the use of threads and the use of
1892 64-bitness are now more daring in the sense that they no more have an
1893 explicit list of operating systems of known threads/64-bit capabili‐
1894 ties. In other words: if your operating system has the necessary APIs
1895 and datatypes, you should be able just to go ahead and use them, for
1896 threads by Configure -Dusethreads, and for 64 bits either explicitly by
1897 Configure -Duse64bitint or implicitly if your system has 64-bit wide
1898 datatypes. See also "64-bit support".
1899 Long Doubles
1901 Some platforms have "long doubles", floating point numbers of even
1903 larger range than ordinary "doubles". To enable using long doubles for
1904 Perl's scalars, use -Duselongdouble.
1905 -Dusemorebits
1907 You can enable both -Duse64bitint and -Duselongdouble with -Duse‐
1909 morebits. See also "64-bit support".
1910 -Duselargefiles
1912 Some platforms support system APIs that are capable of handling large
1914 files (typically, files larger than two gigabytes). Perl will try to
1915 use these APIs if you ask for -Duselargefiles.
1916 See "Large file support" for more information.
1918 installusrbinperl
1920 You can use "Configure -Uinstallusrbinperl" which causes installperl to
1922 skip installing perl also as /usr/bin/perl. This is useful if you pre‐
1923 fer not to modify /usr/bin for some reason or another but harmful
1924 because many scripts assume to find Perl in /usr/bin/perl.
1925 SOCKS support
1927 You can use "Configure -Dusesocks" which causes Perl to probe for the
1929 SOCKS proxy protocol library (v5, not v4). For more information on
1930 SOCKS, see:
1931 http://www.socks.nec.com/
1933 "-A" flag
1935 You can "post-edit" the Configure variables using the Configure "-A"
1937 switch. The editing happens immediately after the platform specific
1938 hints files have been processed but before the actual configuration
1939 process starts. Run "Configure -h" to find out the full "-A" syntax.
1940 Enhanced Installation Directories
1942 The installation structure has been enriched to improve the support for
1944 maintaining multiple versions of perl, to provide locations for vendor-
1945 supplied modules, scripts, and manpages, and to ease maintenance of
1946 locally-added modules, scripts, and manpages. See the section on
1947 Installation Directories in the INSTALL file for complete details. For
1948 most users building and installing from source, the defaults should be
1949 fine.
1950 If you previously used "Configure -Dsitelib" or "-Dsitearch" to set
1952 special values for library directories, you might wish to consider
1953 using the new "-Dsiteprefix" setting instead. Also, if you wish to re-
1954 use a config.sh file from an earlier version of perl, you should be
1955 sure to check that Configure makes sensible choices for the new direc‐
1956 tories. See INSTALL for complete details.
1957 gcc automatically tried if 'cc' does not seem to be working
1959 In many platforms the vendor-supplied 'cc' is too stripped-down to
1961 build Perl (basically, the 'cc' doesn't do ANSI C). If this seems to
1962 be the case and the 'cc' does not seem to be the GNU C compiler 'gcc',
1963 an automatic attempt is made to find and use 'gcc' instead.
1964
1966 Supported platforms
1967 · The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the
1969 Thread extension.
1970 · GNU/Hurd is now supported.
1972 · Rhapsody/Darwin is now supported.
1974 · EPOC is now supported (on Psion 5).
1976 · The cygwin port (formerly cygwin32) has been greatly improved.
1978 DOS
1980 · Perl now works with djgpp 2.02 (and 2.03 alpha).
1982 · Environment variable names are not converted to uppercase any more.
1984 · Incorrect exit codes from backticks have been fixed.
1986 · This port continues to use its own builtin globbing (not
1988 File::Glob).
1989 OS390 (OpenEdition MVS)
1991 Support for this EBCDIC platform has not been renewed in this release.
1993 There are difficulties in reconciling Perl's standardization on UTF-8
1994 as its internal representation for characters with the EBCDIC character
1995 set, because the two are incompatible.
1996 It is unclear whether future versions will renew support for this plat‐
1998 form, but the possibility exists.
1999 VMS
2001 Numerous revisions and extensions to configuration, build, testing, and
2003 installation process to accommodate core changes and VMS-specific
2004 options.
2005 Expand %ENV-handling code to allow runtime mapping to logical names,
2007 CLI symbols, and CRTL environ array.
2008 Extension of subprocess invocation code to accept filespecs as command
2010 "verbs".
2011 Add to Perl command line processing the ability to use default file
2013 types and to recognize Unix-style "2>&1".
2014 Expansion of File::Spec::VMS routines, and integration into ExtU‐
2016 tils::MM_VMS.
2017 Extension of ExtUtils::MM_VMS to handle complex extensions more flexi‐
2019 bly.
2020 Barewords at start of Unix-syntax paths may be treated as text rather
2022 than only as logical names.
2023 Optional secure translation of several logical names used internally by
2025 Perl.
2026 Miscellaneous bugfixing and porting of new core code to VMS.
2028 Thanks are gladly extended to the many people who have contributed VMS
2030 patches, testing, and ideas.
2031 Win32
2033 Perl can now emulate fork() internally, using multiple interpreters
2035 running in different concurrent threads. This support must be enabled
2036 at build time. See perlfork for detailed information.
2037 When given a pathname that consists only of a drivename, such as "A:",
2039 opendir() and stat() now use the current working directory for the
2040 drive rather than the drive root.
2041 The builtin XSUB functions in the Win32:: namespace are documented.
2043 See Win32.
2044 $^X now contains the full path name of the running executable.
2046 A Win32::GetLongPathName() function is provided to complement
2048 Win32::GetFullPathName() and Win32::GetShortPathName(). See Win32.
2049 POSIX::uname() is supported.
2051 system(1,...) now returns true process IDs rather than process handles.
2053 kill() accepts any real process id, rather than strictly return values
2054 from system(1,...).
2055 For better compatibility with Unix, "kill(0, $pid)" can now be used to
2057 test whether a process exists.
2058 The "Shell" module is supported.
2060 Better support for building Perl under command.com in Windows 95 has
2062 been added.
2063 Scripts are read in binary mode by default to allow ByteLoader (and the
2065 filter mechanism in general) to work properly. For compatibility, the
2066 DATA filehandle will be set to text mode if a carriage return is
2067 detected at the end of the line containing the __END__ or __DATA__
2068 token; if not, the DATA filehandle will be left open in binary mode.
2069 Earlier versions always opened the DATA filehandle in text mode.
2070 The glob() operator is implemented via the "File::Glob" extension,
2072 which supports glob syntax of the C shell. This increases the flexi‐
2073 bility of the glob() operator, but there may be compatibility issues
2074 for programs that relied on the older globbing syntax. If you want to
2075 preserve compatibility with the older syntax, you might want to run
2076 perl with "-MFile::DosGlob". For details and compatibility informa‐
2077 tion, see File::Glob.
2078
2080 <HANDLE> on empty files
2081 With $/ set to "undef", "slurping" an empty file returns a string of
2083 zero length (instead of "undef", as it used to) the first time the HAN‐
2084 DLE is read after $/ is set to "undef". Further reads yield "undef".
2085 This means that the following will append "foo" to an empty file (it
2087 used to do nothing):
2088 perl -0777 -pi -e 's/^/foo/' empty_file
2090 The behaviour of:
2092 perl -pi -e 's/^/foo/' empty_file
2094 is unchanged (it continues to leave the file empty).
2096 "eval '...'" improvements
2098 Line numbers (as reflected by caller() and most diagnostics) within
2100 "eval '...'" were often incorrect where here documents were involved.
2101 This has been corrected.
2102 Lexical lookups for variables appearing in "eval '...'" within func‐
2104 tions that were themselves called within an "eval '...'" were searching
2105 the wrong place for lexicals. The lexical search now correctly ends at
2106 the subroutine's block boundary.
2107 The use of "return" within "eval {...}" caused $@ not to be reset cor‐
2109 rectly when no exception occurred within the eval. This has been
2110 fixed.
2111 Parsing of here documents used to be flawed when they appeared as the
2113 replacement expression in "eval 's/.../.../e'". This has been fixed.
2114 All compilation errors are true errors
2116 Some "errors" encountered at compile time were by necessity generated
2118 as warnings followed by eventual termination of the program. This
2119 enabled more such errors to be reported in a single run, rather than
2120 causing a hard stop at the first error that was encountered.
2121 The mechanism for reporting such errors has been reimplemented to queue
2123 compile-time errors and report them at the end of the compilation as
2124 true errors rather than as warnings. This fixes cases where error mes‐
2125 sages leaked through in the form of warnings when code was compiled at
2126 run time using "eval STRING", and also allows such errors to be reli‐
2127 ably trapped using "eval "..."".
2128 Implicitly closed filehandles are safer
2130 Sometimes implicitly closed filehandles (as when they are localized,
2132 and Perl automatically closes them on exiting the scope) could inadver‐
2133 tently set $? or $!. This has been corrected.
2134 Behavior of list slices is more consistent
2136 When taking a slice of a literal list (as opposed to a slice of an
2138 array or hash), Perl used to return an empty list if the result hap‐
2139 pened to be composed of all undef values.
2140 The new behavior is to produce an empty list if (and only if) the orig‐
2142 inal list was empty. Consider the following example:
2143 @a = (1,undef,undef,2)[2,1,2];
2145 The old behavior would have resulted in @a having no elements. The new
2147 behavior ensures it has three undefined elements.
2148 Note in particular that the behavior of slices of the following cases
2150 remains unchanged:
2151 @a = ()[1,2];
2153 @a = (getpwent)[7,0];
2154 @a = (anything_returning_empty_list())[2,1,2];
2155 @a = @b[2,1,2];
2156 @a = @c{'a','b','c'};
2157 See perldata.
2159 "(\$)" prototype and $foo{a}
2161 A scalar reference prototype now correctly allows a hash or array ele‐
2163 ment in that slot.
2164 "goto &sub" and AUTOLOAD
2166 The "goto &sub" construct works correctly when &sub happens to be
2168 autoloaded.
2169 "-bareword" allowed under "use integer"
2171 The autoquoting of barewords preceded by "-" did not work in prior ver‐
2173 sions when the "integer" pragma was enabled. This has been fixed.
2174 Failures in DESTROY()
2176 When code in a destructor threw an exception, it went unnoticed in ear‐
2178 lier versions of Perl, unless someone happened to be looking in $@ just
2179 after the point the destructor happened to run. Such failures are now
2180 visible as warnings when warnings are enabled.
2181 Locale bugs fixed
2183 printf() and sprintf() previously reset the numeric locale back to the
2185 default "C" locale. This has been fixed.
2186 Numbers formatted according to the local numeric locale (such as using
2188 a decimal comma instead of a decimal dot) caused "isn't numeric" warn‐
2189 ings, even while the operations accessing those numbers produced cor‐
2190 rect results. These warnings have been discontinued.
2191 Memory leaks
2193 The "eval 'return sub {...}'" construct could sometimes leak memory.
2195 This has been fixed.
2196 Operations that aren't filehandle constructors used to leak memory when
2198 used on invalid filehandles. This has been fixed.
2199 Constructs that modified @_ could fail to deallocate values in @_ and
2201 thus leak memory. This has been corrected.
2202 Spurious subroutine stubs after failed subroutine calls
2204 Perl could sometimes create empty subroutine stubs when a subroutine
2206 was not found in the package. Such cases stopped later method lookups
2207 from progressing into base packages. This has been corrected.
2208 Taint failures under "-U"
2210 When running in unsafe mode, taint violations could sometimes cause
2212 silent failures. This has been fixed.
2213 END blocks and the "-c" switch
2215 Prior versions used to run BEGIN and END blocks when Perl was run in
2217 compile-only mode. Since this is typically not the expected behavior,
2218 END blocks are not executed anymore when the "-c" switch is used, or if
2219 compilation fails.
2220 See "Support for CHECK blocks" for how to run things when the compile
2222 phase ends.
2223 Potential to leak DATA filehandles
2225 Using the "__DATA__" token creates an implicit filehandle to the file
2227 that contains the token. It is the program's responsibility to close
2228 it when it is done reading from it.
2229 This caveat is now better explained in the documentation. See perl‐
2231 data.
2232
2234 "%s" variable %s masks earlier declaration in same %s
2235 (W misc) A "my" or "our" variable has been redeclared in the cur‐
2236 rent scope or statement, effectively eliminating all access to the
2237 previous instance. This is almost always a typographical error.
2238 Note that the earlier variable will still exist until the end of
2239 the scope or until all closure referents to it are destroyed.
2240 "my sub" not yet implemented
2242 (F) Lexically scoped subroutines are not yet implemented. Don't
2243 try that yet.
2244 "our" variable %s redeclared
2246 (W misc) You seem to have already declared the same global once
2247 before in the current lexical scope.
2248 '!' allowed only after types %s
2250 (F) The '!' is allowed in pack() and unpack() only after certain
2251 types. See "pack" in perlfunc.
2252 / cannot take a count
2254 (F) You had an unpack template indicating a counted-length string,
2255 but you have also specified an explicit size for the string. See
2256 "pack" in perlfunc.
2257 / must be followed by a, A or Z
2259 (F) You had an unpack template indicating a counted-length string,
2260 which must be followed by one of the letters a, A or Z to indicate
2261 what sort of string is to be unpacked. See "pack" in perlfunc.
2262 / must be followed by a*, A* or Z*
2264 (F) You had a pack template indicating a counted-length string,
2265 Currently the only things that can have their length counted are
2266 a*, A* or Z*. See "pack" in perlfunc.
2267 / must follow a numeric type
2269 (F) You had an unpack template that contained a '#', but this did
2270 not follow some numeric unpack specification. See "pack" in perl‐
2271 func.
2272 /%s/: Unrecognized escape \\%c passed through
2274 (W regexp) You used a backslash-character combination which is not
2275 recognized by Perl. This combination appears in an interpolated
2276 variable or a "'"-delimited regular expression. The character was
2277 understood literally.
2278 /%s/: Unrecognized escape \\%c in character class passed through
2280 (W regexp) You used a backslash-character combination which is not
2281 recognized by Perl inside character classes. The character was
2282 understood literally.
2283 /%s/ should probably be written as "%s"
2285 (W syntax) You have used a pattern where Perl expected to find a
2286 string, as in the first argument to "join". Perl will treat the
2287 true or false result of matching the pattern against $_ as the
2288 string, which is probably not what you had in mind.
2289 %s() called too early to check prototype
2291 (W prototype) You've called a function that has a prototype before
2292 the parser saw a definition or declaration for it, and Perl could
2293 not check that the call conforms to the prototype. You need to
2294 either add an early prototype declaration for the subroutine in
2295 question, or move the subroutine definition ahead of the call to
2296 get proper prototype checking. Alternatively, if you are certain
2297 that you're calling the function correctly, you may put an amper‐
2298 sand before the name to avoid the warning. See perlsub.
2299 %s argument is not a HASH or ARRAY element
2301 (F) The argument to exists() must be a hash or array element, such
2302 as:
2303 $foo{$bar}
2305 $ref->{"susie"}[12]
2306 %s argument is not a HASH or ARRAY element or slice
2308 (F) The argument to delete() must be either a hash or array ele‐
2309 ment, such as:
2310 $foo{$bar}
2312 $ref->{"susie"}[12]
2313 or a hash or array slice, such as:
2315 @foo[$bar, $baz, $xyzzy]
2317 @{$ref->[12]}{"susie", "queue"}
2318 %s argument is not a subroutine name
2320 (F) The argument to exists() for "exists &sub" must be a subroutine
2321 name, and not a subroutine call. "exists &sub()" will generate
2322 this error.
2323 %s package attribute may clash with future reserved word: %s
2325 (W reserved) A lowercase attribute name was used that had a pack‐
2326 age-specific handler. That name might have a meaning to Perl
2327 itself some day, even though it doesn't yet. Perhaps you should
2328 use a mixed-case attribute name, instead. See attributes.
2329 (in cleanup) %s
2331 (W misc) This prefix usually indicates that a DESTROY() method
2332 raised the indicated exception. Since destructors are usually
2333 called by the system at arbitrary points during execution, and
2334 often a vast number of times, the warning is issued only once for
2335 any number of failures that would otherwise result in the same mes‐
2336 sage being repeated.
2337 Failure of user callbacks dispatched using the "G_KEEPERR" flag
2339 could also result in this warning. See "G_KEEPERR" in perlcall.
2340 <> should be quotes
2342 (F) You wrote "require <file>" when you should have written
2343 "require 'file'".
2344 Attempt to join self
2346 (F) You tried to join a thread from within itself, which is an
2347 impossible task. You may be joining the wrong thread, or you may
2348 need to move the join() to some other thread.
2349 Bad evalled substitution pattern
2351 (F) You've used the /e switch to evaluate the replacement for a
2352 substitution, but perl found a syntax error in the code to evalu‐
2353 ate, most likely an unexpected right brace '}'.
2354 Bad realloc() ignored
2356 (S) An internal routine called realloc() on something that had
2357 never been malloc()ed in the first place. Mandatory, but can be
2358 disabled by setting environment variable "PERL_BADFREE" to 1.
2359 Bareword found in conditional
2361 (W bareword) The compiler found a bareword where it expected a con‐
2362 ditional, which often indicates that an ⎪⎪ or && was parsed as part
2363 of the last argument of the previous construct, for example:
2364 open FOO ⎪⎪ die;
2366 It may also indicate a misspelled constant that has been inter‐
2368 preted as a bareword:
2369 use constant TYPO => 1;
2371 if (TYOP) { print "foo" }
2372 The "strict" pragma is useful in avoiding such errors.
2374 Binary number > 0b11111111111111111111111111111111 non-portable
2376 (W portable) The binary number you specified is larger than 2**32-1
2377 (4294967295) and therefore non-portable between systems. See perl‐
2378 port for more on portability concerns.
2379 Bit vector size > 32 non-portable
2381 (W portable) Using bit vector sizes larger than 32 is non-portable.
2382 Buffer overflow in prime_env_iter: %s
2384 (W internal) A warning peculiar to VMS. While Perl was preparing
2385 to iterate over %ENV, it encountered a logical name or symbol defi‐
2386 nition which was too long, so it was truncated to the string shown.
2387 Can't check filesystem of script "%s"
2389 (P) For some reason you can't check the filesystem of the script
2390 for nosuid.
2391 Can't declare class for non-scalar %s in "%s"
2393 (S) Currently, only scalar variables can declared with a specific
2394 class qualifier in a "my" or "our" declaration. The semantics may
2395 be extended for other types of variables in future.
2396 Can't declare %s in "%s"
2398 (F) Only scalar, array, and hash variables may be declared as "my"
2399 or "our" variables. They must have ordinary identifiers as names.
2400 Can't ignore signal CHLD, forcing to default
2402 (W signal) Perl has detected that it is being run with the SIGCHLD
2403 signal (sometimes known as SIGCLD) disabled. Since disabling this
2404 signal will interfere with proper determination of exit status of
2405 child processes, Perl has reset the signal to its default value.
2406 This situation typically indicates that the parent program under
2407 which Perl may be running (e.g., cron) is being very careless.
2408 Can't modify non-lvalue subroutine call
2410 (F) Subroutines meant to be used in lvalue context should be
2411 declared as such, see "Lvalue subroutines" in perlsub.
2412 Can't read CRTL environ
2414 (S) A warning peculiar to VMS. Perl tried to read an element of
2415 %ENV from the CRTL's internal environment array and discovered the
2416 array was missing. You need to figure out where your CRTL mis‐
2417 placed its environ or define PERL_ENV_TABLES (see perlvms) so that
2418 environ is not searched.
2419 Can't remove %s: %s, skipping file
2421 (S) You requested an inplace edit without creating a backup file.
2422 Perl was unable to remove the original file to replace it with the
2423 modified file. The file was left unmodified.
2424 Can't return %s from lvalue subroutine
2426 (F) Perl detected an attempt to return illegal lvalues (such as
2427 temporary or readonly values) from a subroutine used as an lvalue.
2428 This is not allowed.
2429 Can't weaken a nonreference
2431 (F) You attempted to weaken something that was not a reference.
2432 Only references can be weakened.
2433 Character class [:%s:] unknown
2435 (F) The class in the character class [: :] syntax is unknown. See
2436 perlre.
2437 Character class syntax [%s] belongs inside character classes
2439 (W unsafe) The character class constructs [: :], [= =], and [. .]
2440 go inside character classes, the [] are part of the construct, for
2441 example: /[012[:alpha:]345]/. Note that [= =] and [. .] are not
2442 currently implemented; they are simply placeholders for future
2443 extensions.
2444 Constant is not %s reference
2446 (F) A constant value (perhaps declared using the "use constant"
2447 pragma) is being dereferenced, but it amounts to the wrong type of
2448 reference. The message indicates the type of reference that was
2449 expected. This usually indicates a syntax error in dereferencing
2450 the constant value. See "Constant Functions" in perlsub and con‐
2451 stant.
2452 constant(%s): %s
2454 (F) The parser found inconsistencies either while attempting to
2455 define an overloaded constant, or when trying to find the character
2456 name specified in the "\N{...}" escape. Perhaps you forgot to load
2457 the corresponding "overload" or "charnames" pragma? See charnames
2458 and overload.
2459 CORE::%s is not a keyword
2461 (F) The CORE:: namespace is reserved for Perl keywords.
2462 defined(@array) is deprecated
2464 (D) defined() is not usually useful on arrays because it checks for
2465 an undefined scalar value. If you want to see if the array is
2466 empty, just use "if (@array) { # not empty }" for example.
2467 defined(%hash) is deprecated
2469 (D) defined() is not usually useful on hashes because it checks for
2470 an undefined scalar value. If you want to see if the hash is
2471 empty, just use "if (%hash) { # not empty }" for example.
2472 Did not produce a valid header
2474 See Server error.
2475 (Did you mean "local" instead of "our"?)
2477 (W misc) Remember that "our" does not localize the declared global
2478 variable. You have declared it again in the same lexical scope,
2479 which seems superfluous.
2480 Document contains no data
2482 See Server error.
2483 entering effective %s failed
2485 (F) While under the "use filetest" pragma, switching the real and
2486 effective uids or gids failed.
2487 false [] range "%s" in regexp
2489 (W regexp) A character class range must start and end at a literal
2490 character, not another character class like "\d" or "[:alpha:]".
2491 The "-" in your false range is interpreted as a literal "-". Con‐
2492 sider quoting the "-", "\-". See perlre.
2493 Filehandle %s opened only for output
2495 (W io) You tried to read from a filehandle opened only for writing.
2496 If you intended it to be a read/write filehandle, you needed to
2497 open it with "+<" or "+>" or "+>>" instead of with "<" or nothing.
2498 If you intended only to read from the file, use "<". See "open" in
2499 perlfunc.
2500 flock() on closed filehandle %s
2502 (W closed) The filehandle you're attempting to flock() got itself
2503 closed some time before now. Check your logic flow. flock() oper‐
2504 ates on filehandles. Are you attempting to call flock() on a
2505 dirhandle by the same name?
2506 Global symbol "%s" requires explicit package name
2508 (F) You've said "use strict vars", which indicates that all vari‐
2509 ables must either be lexically scoped (using "my"), declared
2510 beforehand using "our", or explicitly qualified to say which pack‐
2511 age the global variable is in (using "::").
2512 Hexadecimal number > 0xffffffff non-portable
2514 (W portable) The hexadecimal number you specified is larger than
2515 2**32-1 (4294967295) and therefore non-portable between systems.
2516 See perlport for more on portability concerns.
2517 Ill-formed CRTL environ value "%s"
2519 (W internal) A warning peculiar to VMS. Perl tried to read the
2520 CRTL's internal environ array, and encountered an element without
2521 the "=" delimiter used to separate keys from values. The element
2522 is ignored.
2523 Ill-formed message in prime_env_iter: ⎪%s⎪
2525 (W internal) A warning peculiar to VMS. Perl tried to read a logi‐
2526 cal name or CLI symbol definition when preparing to iterate over
2527 %ENV, and didn't see the expected delimiter between key and value,
2528 so the line was ignored.
2529 Illegal binary digit %s
2531 (F) You used a digit other than 0 or 1 in a binary number.
2532 Illegal binary digit %s ignored
2534 (W digit) You may have tried to use a digit other than 0 or 1 in a
2535 binary number. Interpretation of the binary number stopped before
2536 the offending digit.
2537 Illegal number of bits in vec
2539 (F) The number of bits in vec() (the third argument) must be a
2540 power of two from 1 to 32 (or 64, if your platform supports that).
2541 Integer overflow in %s number
2543 (W overflow) The hexadecimal, octal or binary number you have spec‐
2544 ified either as a literal or as an argument to hex() or oct() is
2545 too big for your architecture, and has been converted to a floating
2546 point number. On a 32-bit architecture the largest hexadecimal,
2547 octal or binary number representable without overflow is
2548 0xFFFFFFFF, 037777777777, or 0b11111111111111111111111111111111
2549 respectively. Note that Perl transparently promotes all numbers to
2550 a floating point representation internally--subject to loss of pre‐
2551 cision errors in subsequent operations.
2552 Invalid %s attribute: %s
2554 The indicated attribute for a subroutine or variable was not recog‐
2555 nized by Perl or by a user-supplied handler. See attributes.
2556 Invalid %s attributes: %s
2558 The indicated attributes for a subroutine or variable were not rec‐
2559 ognized by Perl or by a user-supplied handler. See attributes.
2560 invalid [] range "%s" in regexp
2562 The offending range is now explicitly displayed.
2563 Invalid separator character %s in attribute list
2565 (F) Something other than a colon or whitespace was seen between the
2566 elements of an attribute list. If the previous attribute had a
2567 parenthesised parameter list, perhaps that list was terminated too
2568 soon. See attributes.
2569 Invalid separator character %s in subroutine attribute list
2571 (F) Something other than a colon or whitespace was seen between the
2572 elements of a subroutine attribute list. If the previous attribute
2573 had a parenthesised parameter list, perhaps that list was termi‐
2574 nated too soon.
2575 leaving effective %s failed
2577 (F) While under the "use filetest" pragma, switching the real and
2578 effective uids or gids failed.
2579 Lvalue subs returning %s not implemented yet
2581 (F) Due to limitations in the current implementation, array and
2582 hash values cannot be returned in subroutines used in lvalue con‐
2583 text. See "Lvalue subroutines" in perlsub.
2584 Method %s not permitted
2586 See Server error.
2587 Missing %sbrace%s on \N{}
2589 (F) Wrong syntax of character name literal "\N{charname}" within
2590 double-quotish context.
2591 Missing command in piped open
2593 (W pipe) You used the "open(FH, "⎪ command")" or "open(FH, "command
2594 ⎪")" construction, but the command was missing or blank.
2595 Missing name in "my sub"
2597 (F) The reserved syntax for lexically scoped subroutines requires
2598 that they have a name with which they can be found.
2599 No %s specified for -%c
2601 (F) The indicated command line switch needs a mandatory argument,
2602 but you haven't specified one.
2603 No package name allowed for variable %s in "our"
2605 (F) Fully qualified variable names are not allowed in "our" decla‐
2606 rations, because that doesn't make much sense under existing seman‐
2607 tics. Such syntax is reserved for future extensions.
2608 No space allowed after -%c
2610 (F) The argument to the indicated command line switch must follow
2611 immediately after the switch, without intervening spaces.
2612 no UTC offset information; assuming local time is UTC
2614 (S) A warning peculiar to VMS. Perl was unable to find the local
2615 timezone offset, so it's assuming that local system time is equiva‐
2616 lent to UTC. If it's not, define the logical name SYS$TIME‐
2617 ZONE_DIFFERENTIAL to translate to the number of seconds which need
2618 to be added to UTC to get local time.
2619 Octal number > 037777777777 non-portable
2621 (W portable) The octal number you specified is larger than 2**32-1
2622 (4294967295) and therefore non-portable between systems. See perl‐
2623 port for more on portability concerns.
2624 See also perlport for writing portable code.
2626 panic: del_backref
2628 (P) Failed an internal consistency check while trying to reset a
2629 weak reference.
2630 panic: kid popen errno read
2632 (F) forked child returned an incomprehensible message about its
2633 errno.
2634 panic: magic_killbackrefs
2636 (P) Failed an internal consistency check while trying to reset all
2637 weak references to an object.
2638 Parentheses missing around "%s" list
2640 (W parenthesis) You said something like
2641 my $foo, $bar = @_;
2643 when you meant
2645 my ($foo, $bar) = @_;
2647 Remember that "my", "our", and "local" bind tighter than comma.
2649 Possible unintended interpolation of %s in string
2651 (W ambiguous) It used to be that Perl would try to guess whether
2652 you wanted an array interpolated or a literal @. It no longer does
2653 this; arrays are now always interpolated into strings. This means
2654 that if you try something like:
2655 print "fred@example.com";
2657 and the array @example doesn't exist, Perl is going to print
2659 "fred.com", which is probably not what you wanted. To get a lit‐
2660 eral "@" sign in a string, put a backslash before it, just as you
2661 would to get a literal "$" sign.
2662 Possible Y2K bug: %s
2664 (W y2k) You are concatenating the number 19 with another number,
2665 which could be a potential Year 2000 problem.
2666 pragma "attrs" is deprecated, use "sub NAME : ATTRS" instead
2668 (W deprecated) You have written something like this:
2669 sub doit
2671 {
2672 use attrs qw(locked);
2673 }
2674 You should use the new declaration syntax instead.
2676 sub doit : locked
2678 {
2679 ...
2680 The "use attrs" pragma is now obsolete, and is only provided for
2682 backward-compatibility. See "Subroutine Attributes" in perlsub.
2683 Premature end of script headers
2685 See Server error.
2686 Repeat count in pack overflows
2688 (F) You can't specify a repeat count so large that it overflows
2689 your signed integers. See "pack" in perlfunc.
2690 Repeat count in unpack overflows
2692 (F) You can't specify a repeat count so large that it overflows
2693 your signed integers. See "unpack" in perlfunc.
2694 realloc() of freed memory ignored
2696 (S) An internal routine called realloc() on something that had
2697 already been freed.
2698 Reference is already weak
2700 (W misc) You have attempted to weaken a reference that is already
2701 weak. Doing so has no effect.
2702 setpgrp can't take arguments
2704 (F) Your system has the setpgrp() from BSD 4.2, which takes no
2705 arguments, unlike POSIX setpgid(), which takes a process ID and
2706 process group ID.
2707 Strange *+?{} on zero-length expression
2709 (W regexp) You applied a regular expression quantifier in a place
2710 where it makes no sense, such as on a zero-width assertion. Try
2711 putting the quantifier inside the assertion instead. For example,
2712 the way to match "abc" provided that it is followed by three repe‐
2713 titions of "xyz" is "/abc(?=(?:xyz){3})/", not "/abc(?=xyz){3}/".
2714 switching effective %s is not implemented
2716 (F) While under the "use filetest" pragma, we cannot switch the
2717 real and effective uids or gids.
2718 This Perl can't reset CRTL environ elements (%s)
2720 This Perl can't set CRTL environ elements (%s=%s)
2721 (W internal) Warnings peculiar to VMS. You tried to change or
2722 delete an element of the CRTL's internal environ array, but your
2723 copy of Perl wasn't built with a CRTL that contained the setenv()
2724 function. You'll need to rebuild Perl with a CRTL that does, or
2725 redefine PERL_ENV_TABLES (see perlvms) so that the environ array
2726 isn't the target of the change to %ENV which produced the warning.
2727 Too late to run %s block
2729 (W void) A CHECK or INIT block is being defined during run time
2730 proper, when the opportunity to run them has already passed. Per‐
2731 haps you are loading a file with "require" or "do" when you should
2732 be using "use" instead. Or perhaps you should put the "require" or
2733 "do" inside a BEGIN block.
2734 Unknown open() mode '%s'
2736 (F) The second argument of 3-argument open() is not among the list
2737 of valid modes: "<", ">", ">>", "+<", "+>", "+>>", "-⎪", "⎪-".
2738 Unknown process %x sent message to prime_env_iter: %s
2740 (P) An error peculiar to VMS. Perl was reading values for %ENV
2741 before iterating over it, and someone else stuck a message in the
2742 stream of data Perl expected. Someone's very confused, or perhaps
2743 trying to subvert Perl's population of %ENV for nefarious purposes.
2744 Unrecognized escape \\%c passed through
2746 (W misc) You used a backslash-character combination which is not
2747 recognized by Perl. The character was understood literally.
2748 Unterminated attribute parameter in attribute list
2750 (F) The lexer saw an opening (left) parenthesis character while
2751 parsing an attribute list, but the matching closing (right) paren‐
2752 thesis character was not found. You may need to add (or remove) a
2753 backslash character to get your parentheses to balance. See
2754 attributes.
2755 Unterminated attribute list
2757 (F) The lexer found something other than a simple identifier at the
2758 start of an attribute, and it wasn't a semicolon or the start of a
2759 block. Perhaps you terminated the parameter list of the previous
2760 attribute too soon. See attributes.
2761 Unterminated attribute parameter in subroutine attribute list
2763 (F) The lexer saw an opening (left) parenthesis character while
2764 parsing a subroutine attribute list, but the matching closing
2765 (right) parenthesis character was not found. You may need to add
2766 (or remove) a backslash character to get your parentheses to bal‐
2767 ance.
2768 Unterminated subroutine attribute list
2770 (F) The lexer found something other than a simple identifier at the
2771 start of a subroutine attribute, and it wasn't a semicolon or the
2772 start of a block. Perhaps you terminated the parameter list of the
2773 previous attribute too soon.
2774 Value of CLI symbol "%s" too long
2776 (W misc) A warning peculiar to VMS. Perl tried to read the value
2777 of an %ENV element from a CLI symbol table, and found a resultant
2778 string longer than 1024 characters. The return value has been
2779 truncated to 1024 characters.
2780 Version number must be a constant number
2782 (P) The attempt to translate a "use Module n.n LIST" statement into
2783 its equivalent "BEGIN" block found an internal inconsistency with
2784 the version number.
2785
2787 lib/attrs
2788 Compatibility tests for "sub : attrs" vs the older "use attrs".
2789 lib/env
2791 Tests for new environment scalar capability (e.g., "use Env
2792 qw($BAR);").
2793 lib/env-array
2795 Tests for new environment array capability (e.g., "use Env
2796 qw(@PATH);").
2797 lib/io_const
2799 IO constants (SEEK_*, _IO*).
2800 lib/io_dir
2802 Directory-related IO methods (new, read, close, rewind, tied
2803 delete).
2804 lib/io_multihomed
2806 INET sockets with multi-homed hosts.
2807 lib/io_poll
2809 IO poll().
2810 lib/io_unix
2812 UNIX sockets.
2813 op/attrs
2815 Regression tests for "my ($x,@y,%z) : attrs" and <sub : attrs>.
2816 op/filetest
2818 File test operators.
2819 op/lex_assign
2821 Verify operations that access pad objects (lexicals and tempo‐
2822 raries).
2823 op/exists_sub
2825 Verify "exists &sub" operations.
2826
2828 Perl Source Incompatibilities
2829 Beware that any new warnings that have been added or old ones that have
2831 been enhanced are not considered incompatible changes.
2832 Since all new warnings must be explicitly requested via the "-w" switch
2834 or the "warnings" pragma, it is ultimately the programmer's responsi‐
2835 bility to ensure that warnings are enabled judiciously.
2836 CHECK is a new keyword
2838 All subroutine definitions named CHECK are now special. See
2839 "/"Support for CHECK blocks"" for more information.
2840 Treatment of list slices of undef has changed
2842 There is a potential incompatibility in the behavior of list slices
2843 that are comprised entirely of undefined values. See "Behavior of
2844 list slices is more consistent".
2845 Format of $English::PERL_VERSION is different
2847 The English module now sets $PERL_VERSION to $^V (a string value)
2848 rather than $] (a numeric value). This is a potential incompati‐
2849 bility. Send us a report via perlbug if you are affected by this.
2850 See "Improved Perl version numbering system" for the reasons for
2852 this change.
2853 Literals of the form 1.2.3 parse differently
2855 Previously, numeric literals with more than one dot in them were
2856 interpreted as a floating point number concatenated with one or
2857 more numbers. Such "numbers" are now parsed as strings composed of
2858 the specified ordinals.
2859 For example, "print 97.98.99" used to output 97.9899 in earlier
2861 versions, but now prints "abc".
2862 See "Support for strings represented as a vector of ordinals".
2864 Possibly changed pseudo-random number generator
2866 Perl programs that depend on reproducing a specific set of pseudo-
2867 random numbers may now produce different output due to improvements
2868 made to the rand() builtin. You can use "sh Configure -Drand‐
2869 func=rand" to obtain the old behavior.
2870 See "Better pseudo-random number generator".
2872 Hashing function for hash keys has changed
2874 Even though Perl hashes are not order preserving, the apparently
2875 random order encountered when iterating on the contents of a hash
2876 is actually determined by the hashing algorithm used. Improvements
2877 in the algorithm may yield a random order that is different from
2878 that of previous versions, especially when iterating on hashes.
2879 See "Better worst-case behavior of hashes" for additional informa‐
2881 tion.
2882 "undef" fails on read only values
2884 Using the "undef" operator on a readonly value (such as $1) has the
2885 same effect as assigning "undef" to the readonly value--it throws
2886 an exception.
2887 Close-on-exec bit may be set on pipe and socket handles
2889 Pipe and socket handles are also now subject to the close-on-exec
2890 behavior determined by the special variable $^F.
2891 See "More consistent close-on-exec behavior".
2893 Writing "$$1" to mean "${$}1" is unsupported
2895 Perl 5.004 deprecated the interpretation of $$1 and similar within
2896 interpolated strings to mean "$$ . "1"", but still allowed it.
2897 In Perl 5.6.0 and later, "$$1" always means "${$1}".
2899 delete(), each(), values() and "\(%h)"
2901 operate on aliases to values, not copies
2902 delete(), each(), values() and hashes (e.g. "\(%h)") in a list con‐
2904 text return the actual values in the hash, instead of copies (as
2905 they used to in earlier versions). Typical idioms for using these
2906 constructs copy the returned values, but this can make a signifi‐
2907 cant difference when creating references to the returned values.
2908 Keys in the hash are still returned as copies when iterating on a
2909 hash.
2910 See also "delete(), each(), values() and hash iteration are
2912 faster".
2913 vec(EXPR,OFFSET,BITS) enforces powers-of-two BITS
2915 vec() generates a run-time error if the BITS argument is not a
2916 valid power-of-two integer.
2917 Text of some diagnostic output has changed
2919 Most references to internal Perl operations in diagnostics have
2920 been changed to be more descriptive. This may be an issue for pro‐
2921 grams that may incorrectly rely on the exact text of diagnostics
2922 for proper functioning.
2923 "%@" has been removed
2925 The undocumented special variable "%@" that used to accumulate
2926 "background" errors (such as those that happen in DESTROY()) has
2927 been removed, because it could potentially result in memory leaks.
2928 Parenthesized not() behaves like a list operator
2930 The "not" operator now falls under the "if it looks like a func‐
2931 tion, it behaves like a function" rule.
2932 As a result, the parenthesized form can be used with "grep" and
2934 "map". The following construct used to be a syntax error before,
2935 but it works as expected now:
2936 grep not($_), @things;
2938 On the other hand, using "not" with a literal list slice may not
2940 work. The following previously allowed construct:
2941 print not (1,2,3)[0];
2943 needs to be written with additional parentheses now:
2945 print not((1,2,3)[0]);
2947 The behavior remains unaffected when "not" is not followed by
2949 parentheses.
2950 Semantics of bareword prototype "(*)" have changed
2952 The semantics of the bareword prototype "*" have changed. Perl
2953 5.005 always coerced simple scalar arguments to a typeglob, which
2954 wasn't useful in situations where the subroutine must distinguish
2955 between a simple scalar and a typeglob. The new behavior is to not
2956 coerce bareword arguments to a typeglob. The value will always be
2957 visible as either a simple scalar or as a reference to a typeglob.
2958 See "More functional bareword prototype (*)".
2960 Semantics of bit operators may have changed on 64-bit platforms
2962 If your platform is either natively 64-bit or if Perl has been con‐
2963 figured to used 64-bit integers, i.e., $Config{ivsize} is 8, there
2964 may be a potential incompatibility in the behavior of bitwise
2965 numeric operators (& ⎪ ^ ~ << >>). These operators used to
2966 strictly operate on the lower 32 bits of integers in previous ver‐
2967 sions, but now operate over the entire native integral width. In
2968 particular, note that unary "~" will produce different results on
2969 platforms that have different $Config{ivsize}. For portability, be
2970 sure to mask off the excess bits in the result of unary "~", e.g.,
2971 "~$x & 0xffffffff".
2972 See "Bit operators support full native integer width".
2974 More builtins taint their results
2976 As described in "Improved security features", there may be more
2977 sources of taint in a Perl program.
2978 To avoid these new tainting behaviors, you can build Perl with the
2980 Configure option "-Accflags=-DINCOMPLETE_TAINTS". Beware that the
2981 ensuing perl binary may be insecure.
2982 C Source Incompatibilities
2984 "PERL_POLLUTE"
2986 Release 5.005 grandfathered old global symbol names by providing
2987 preprocessor macros for extension source compatibility. As of
2988 release 5.6.0, these preprocessor definitions are not available by
2989 default. You need to explicitly compile perl with "-DPERL_POLLUTE"
2990 to get these definitions. For extensions still using the old sym‐
2991 bols, this option can be specified via MakeMaker:
2992 perl Makefile.PL POLLUTE=1
2994 "PERL_IMPLICIT_CONTEXT"
2996 This new build option provides a set of macros for all API func‐
2997 tions such that an implicit interpreter/thread context argument is
2998 passed to every API function. As a result of this, something like
2999 "sv_setsv(foo,bar)" amounts to a macro invocation that actually
3000 translates to something like "Perl_sv_setsv(my_perl,foo,bar)".
3001 While this is generally expected to not have any significant source
3002 compatibility issues, the difference between a macro and a real
3003 function call will need to be considered.
3004 This means that there is a source compatibility issue as a result
3006 of this if your extensions attempt to use pointers to any of the
3007 Perl API functions.
3008 Note that the above issue is not relevant to the default build of
3010 Perl, whose interfaces continue to match those of prior versions
3011 (but subject to the other options described here).
3012 See "The Perl API" in perlguts for detailed information on the ram‐
3014 ifications of building Perl with this option.
3015 NOTE: PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
3017 with one of -Dusethreads, -Dusemultiplicity, or both. It is not
3018 intended to be enabled by users at this time.
3019 "PERL_POLLUTE_MALLOC"
3021 Enabling Perl's malloc in release 5.005 and earlier caused the
3022 namespace of the system's malloc family of functions to be usurped
3023 by the Perl versions, since by default they used the same names.
3024 Besides causing problems on platforms that do not allow these func‐
3025 tions to be cleanly replaced, this also meant that the system ver‐
3026 sions could not be called in programs that used Perl's malloc.
3027 Previous versions of Perl have allowed this behaviour to be sup‐
3028 pressed with the HIDEMYMALLOC and EMBEDMYMALLOC preprocessor defi‐
3029 nitions.
3030 As of release 5.6.0, Perl's malloc family of functions have default
3032 names distinct from the system versions. You need to explicitly
3033 compile perl with "-DPERL_POLLUTE_MALLOC" to get the older behav‐
3034 iour. HIDEMYMALLOC and EMBEDMYMALLOC have no effect, since the be‐
3035 haviour they enabled is now the default.
3036 Note that these functions do not constitute Perl's memory alloca‐
3038 tion API. See "Memory Allocation" in perlguts for further informa‐
3039 tion about that.
3040 Compatible C Source API Changes
3042 "PATCHLEVEL" is now "PERL_VERSION"
3044 The cpp macros "PERL_REVISION", "PERL_VERSION", and "PERL_SUBVER‐
3045 SION" are now available by default from perl.h, and reflect the
3046 base revision, patchlevel, and subversion respectively.
3047 "PERL_REVISION" had no prior equivalent, while "PERL_VERSION" and
3048 "PERL_SUBVERSION" were previously available as "PATCHLEVEL" and
3049 "SUBVERSION".
3050 The new names cause less pollution of the cpp namespace and reflect
3052 what the numbers have come to stand for in common practice. For
3053 compatibility, the old names are still supported when patchlevel.h
3054 is explicitly included (as required before), so there is no source
3055 incompatibility from the change.
3056 Binary Incompatibilities
3058 In general, the default build of this release is expected to be binary
3060 compatible for extensions built with the 5.005 release or its mainte‐
3061 nance versions. However, specific platforms may have broken binary
3062 compatibility due to changes in the defaults used in hints files.
3063 Therefore, please be sure to always check the platform-specific README
3064 files for any notes to the contrary.
3065 The usethreads or usemultiplicity builds are not binary compatible with
3067 the corresponding builds in 5.005.
3068 On platforms that require an explicit list of exports (AIX, OS/2 and
3070 Windows, among others), purely internal symbols such as parser func‐
3071 tions and the run time opcodes are not exported by default. Perl 5.005
3072 used to export all functions irrespective of whether they were consid‐
3073 ered part of the public API or not.
3074 For the full list of public API functions, see perlapi.
3076
3078 Localizing a tied hash element may leak memory
3079 As of the 5.6.1 release, there is a known leak when code such as this
3081 is executed:
3082 use Tie::Hash;
3084 tie my %tie_hash => 'Tie::StdHash';
3085 ...
3087 local($tie_hash{Foo}) = 1; # leaks
3089 Known test failures
3091 · 64-bit builds
3093 Subtest #15 of lib/b.t may fail under 64-bit builds on platforms
3095 such as HP-UX PA64 and Linux IA64. The issue is still being inves‐
3096 tigated.
3097 The lib/io_multihomed test may hang in HP-UX if Perl has been con‐
3099 figured to be 64-bit. Because other 64-bit platforms do not hang
3100 in this test, HP-UX is suspect. All other tests pass in 64-bit
3101 HP-UX. The test attempts to create and connect to "multihomed"
3102 sockets (sockets which have multiple IP addresses).
3103 Note that 64-bit support is still experimental.
3105 · Failure of Thread tests
3107 The subtests 19 and 20 of lib/thr5005.t test are known to fail due
3109 to fundamental problems in the 5.005 threading implementation.
3110 These are not new failures--Perl 5.005_0x has the same bugs, but
3111 didn't have these tests. (Note that support for 5.005-style
3112 threading remains experimental.)
3113 · NEXTSTEP 3.3 POSIX test failure
3115 In NEXTSTEP 3.3p2 the implementation of the strftime(3) in the
3117 operating system libraries is buggy: the %j format numbers the days
3118 of a month starting from zero, which, while being logical to pro‐
3119 grammers, will cause the subtests 19 to 27 of the lib/posix test
3120 may fail.
3121 · Tru64 (aka Digital UNIX, aka DEC OSF/1) lib/sdbm test failure with
3123 gcc
3124 If compiled with gcc 2.95 the lib/sdbm test will fail (dump core).
3126 The cure is to use the vendor cc, it comes with the operating sys‐
3127 tem and produces good code.
3128 EBCDIC platforms not fully supported
3130 In earlier releases of Perl, EBCDIC environments like OS390 (also known
3132 as Open Edition MVS) and VM-ESA were supported. Due to changes
3133 required by the UTF-8 (Unicode) support, the EBCDIC platforms are not
3134 supported in Perl 5.6.0.
3135 The 5.6.1 release improves support for EBCDIC platforms, but they are
3137 not fully supported yet.
3138 UNICOS/mk CC failures during Configure run
3140 In UNICOS/mk the following errors may appear during the Configure run:
3142 Guessing which symbols your C compiler and preprocessor define...
3144 CC-20 cc: ERROR File = try.c, Line = 3
3145 ...
3146 bad switch yylook 79bad switch yylook 79bad switch yylook 79bad switch yylook 79#ifdef A29K
3147 ...
3148 4 errors detected in the compilation of "try.c".
3149 The culprit is the broken awk of UNICOS/mk. The effect is fortunately
3151 rather mild: Perl itself is not adversely affected by the error, only
3152 the h2ph utility coming with Perl, and that is rather rarely needed
3153 these days.
3154 Arrow operator and arrays
3156 When the left argument to the arrow operator "->" is an array, or the
3158 "scalar" operator operating on an array, the result of the operation
3159 must be considered erroneous. For example:
3160 @x->[2]
3162 scalar(@x)->[2]
3163 These expressions will get run-time errors in some future release of
3165 Perl.
3166 Experimental features
3168 As discussed above, many features are still experimental. Interfaces
3170 and implementation of these features are subject to change, and in
3171 extreme cases, even subject to removal in some future release of Perl.
3172 These features include the following:
3173 Threads
3175 Unicode
3176 64-bit support
3177 Lvalue subroutines
3178 Weak references
3179 The pseudo-hash data type
3180 The Compiler suite
3181 Internal implementation of file globbing
3182 The DB module
3183 The regular expression code constructs:
3184 "(?{ code })" and "(??{ code })"
3185
3187 Character class syntax [: :] is reserved for future extensions
3188 (W) Within regular expression character classes ([]) the syntax
3189 beginning with "[:" and ending with ":]" is reserved for future
3190 extensions. If you need to represent those character sequences
3191 inside a regular expression character class, just quote the square
3192 brackets with the backslash: "\[:" and ":\]".
3193 Ill-formed logical name ⎪%s⎪ in prime_env_iter
3195 (W) A warning peculiar to VMS. A logical name was encountered when
3196 preparing to iterate over %ENV which violates the syntactic rules
3197 governing logical names. Because it cannot be translated normally,
3198 it is skipped, and will not appear in %ENV. This may be a benign
3199 occurrence, as some software packages might directly modify logical
3200 name tables and introduce nonstandard names, or it may indicate
3201 that a logical name table has been corrupted.
3202 In string, @%s now must be written as \@%s
3204 The description of this error used to say:
3205 (Someday it will simply assume that an unbackslashed @
3207 interpolates an array.)
3208 That day has come, and this fatal error has been removed. It has
3210 been replaced by a non-fatal warning instead. See "Arrays now
3211 always interpolate into double-quoted strings" for details.
3212 Probable precedence problem on %s
3214 (W) The compiler found a bareword where it expected a conditional,
3215 which often indicates that an ⎪⎪ or && was parsed as part of the
3216 last argument of the previous construct, for example:
3217 open FOO ⎪⎪ die;
3219 regexp too big
3221 (F) The current implementation of regular expressions uses shorts
3222 as address offsets within a string. Unfortunately this means that
3223 if the regular expression compiles to longer than 32767, it'll blow
3224 up. Usually when you want a regular expression this big, there is
3225 a better way to do it with multiple statements. See perlre.
3226 Use of "$$<digit>" to mean "${$}<digit>" is deprecated
3228 (D) Perl versions before 5.004 misinterpreted any type marker fol‐
3229 lowed by "$" and a digit. For example, "$$0" was incorrectly taken
3230 to mean "${$}0" instead of "${$0}". This bug is (mostly) fixed in
3231 Perl 5.004.
3232 However, the developers of Perl 5.004 could not fix this bug com‐
3234 pletely, because at least two widely-used modules depend on the old
3235 meaning of "$$0" in a string. So Perl 5.004 still interprets
3236 "$$<digit>" in the old (broken) way inside strings; but it gener‐
3237 ates this message as a warning. And in Perl 5.005, this special
3238 treatment will cease.
3239
3241 If you find what you think is a bug, you might check the articles
3242 recently posted to the comp.lang.perl.misc newsgroup. There may also
3243 be information at http://www.perl.com/ , the Perl Home Page.
3244 If you believe you have an unreported bug, please run the perlbug pro‐
3246 gram included with your release. Be sure to trim your bug down to a
3247 tiny but sufficient test case. Your bug report, along with the output
3248 of "perl -V", will be sent off to perlbug@perl.org to be analysed by
3249 the Perl porting team.
3250
3252 The Changes file for exhaustive details on what changed.
3253 The INSTALL file for how to build Perl.
3255 The README file for general stuff.
3257 The Artistic and Copying files for copyright information.
3259
3261 Written by Gurusamy Sarathy <gsar@ActiveState.com>, with many contribu‐
3262 tions from The Perl Porters.
3263 Send omissions or corrections to <perlbug@perl.org>.
3265perl v5.8.8 2006-01-07 PERL561DELTA(1)