1PERL561DELTA(1) Perl Programmers Reference Guide PERL561DELTA(1)
2
6 perl561delta - what's new for perl v5.6.1
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
15 mentioned here may be found in the Changes files that accompany the
16 Perl source distribution. See perlhack for pointers to online
17 resources where you can inspect the individual patches described by
18 these changes.
19 Security Issues
21 suidperl will not run /bin/mail anymore, because some platforms have a
22 /bin/mail that is vulnerable to buffer overflow attacks.
23 Note that suidperl is neither built nor installed by default in any
25 recent version of perl. Use of suidperl is highly discouraged. If you
26 think you need it, try alternatives such as sudo first. See
27 http://www.courtesan.com/sudo/ .
28 Core bug fixes
30 This is not an exhaustive list. It is intended to cover only the
31 significant user-visible changes.
32 "UNIVERSAL::isa()"
34 A bug in the caching mechanism used by "UNIVERSAL::isa()" that
35 affected base.pm has been fixed. The bug has existed since the
36 5.005 releases, but wasn't tickled by base.pm in those releases.
37 Memory leaks
39 Various cases of memory leaks and attempts to access uninitialized
40 memory have been cured. See "Known Problems" below for further
41 issues.
42 Numeric conversions
44 Numeric conversions did not recognize changes in the string value
45 properly in certain circumstances.
46 In other situations, large unsigned numbers (those above 2**31)
48 could sometimes lose their unsignedness, causing bogus results in
49 arithmetic operations.
50 Integer modulus on large unsigned integers sometimes returned
52 incorrect values.
53 Perl 5.6.0 generated "not a number" warnings on certain conversions
55 where previous versions didn't.
56 These problems have all been rectified.
58 Infinity is now recognized as a number.
60 qw(a\\b)
62 In Perl 5.6.0, qw(a\\b) produced a string with two backslashes
63 instead of one, in a departure from the behavior in previous
64 versions. The older behavior has been reinstated.
65 caller()
67 caller() could cause core dumps in certain situations. Carp was
68 sometimes affected by this problem.
69 Bugs in regular expressions
71 Pattern matches on overloaded values are now handled correctly.
72 Perl 5.6.0 parsed m/\x{ab}/ incorrectly, leading to spurious
74 warnings. This has been corrected.
75 The RE engine found in Perl 5.6.0 accidentally pessimised certain
77 kinds of simple pattern matches. These are now handled better.
78 Regular expression debug output (whether through "use re 'debug'"
80 or via "-Dr") now looks better.
81 Multi-line matches like ""a\nxb\n" =~ /(?!\A)x/m" were flawed. The
83 bug has been fixed.
84 Use of $& could trigger a core dump under some situations. This is
86 now avoided.
87 Match variables $1 et al., weren't being unset when a pattern match
89 was backtracking, and the anomaly showed up inside "/...(?{ ...
90 }).../" etc. These variables are now tracked correctly.
91 pos() did not return the correct value within s///ge in earlier
93 versions. This is now handled correctly.
94 "slurp" mode
96 readline() on files opened in "slurp" mode could return an extra ""
97 at the end in certain situations. This has been corrected.
98 Autovivification of symbolic references to special variables
100 Autovivification of symbolic references of special variables
101 described in perlvar (as in "${$num}") was accidentally disabled.
102 This works again now.
103 Lexical warnings
105 Lexical warnings now propagate correctly into "eval "..."".
106 "use warnings qw(FATAL all)" did not work as intended. This has
108 been corrected.
109 Lexical warnings could leak into other scopes in some situations.
111 This is now fixed.
112 warnings::enabled() now reports the state of $^W correctly if the
114 caller isn't using lexical warnings.
115 Spurious warnings and errors
117 Perl 5.6.0 could emit spurious warnings about redefinition of
118 dl_error() when statically building extensions into perl. This has
119 been corrected.
120 "our" variables could result in bogus "Variable will not stay
122 shared" warnings. This is now fixed.
123 "our" variables of the same name declared in two sibling blocks
125 resulted in bogus warnings about "redeclaration" of the variables.
126 The problem has been corrected.
127 glob()
129 Compatibility of the builtin glob() with old csh-based glob has
130 been improved with the addition of GLOB_ALPHASORT option. See
131 "File::Glob".
132 File::Glob::glob() has been renamed to File::Glob::bsd_glob()
134 because the name clashes with the builtin glob(). The older name
135 is still available for compatibility, but is deprecated.
136 Spurious syntax errors generated in certain situations, when glob()
138 caused File::Glob to be loaded for the first time, have been fixed.
139 Tainting
141 Some cases of inconsistent taint propagation (such as within hash
142 values) have been fixed.
143 The tainting behavior of sprintf() has been rationalized. It does
145 not taint the result of floating point formats anymore, making the
146 behavior consistent with that of string interpolation.
147 sort()
149 Arguments to sort() weren't being provided the right wantarray()
150 context. The comparison block is now run in scalar context, and
151 the arguments to be sorted are always provided list context.
152 sort() is also fully reentrant, in the sense that the sort function
154 can itself call sort(). This did not work reliably in previous
155 releases.
156 #line directives
158 #line directives now work correctly when they appear at the very
159 beginning of "eval "..."".
160 Subroutine prototypes
162 The (\&) prototype now works properly.
163 map()
165 map() could get pathologically slow when the result list it
166 generates is larger than the source list. The performance has been
167 improved for common scenarios.
168 Debugger
170 Debugger exit code now reflects the script exit code.
171 Condition "0" in breakpoints is now treated correctly.
173 The "d" command now checks the line number.
175 $. is no longer corrupted by the debugger.
177 All debugger output now correctly goes to the socket if RemotePort
179 is set.
180 PERL5OPT
182 PERL5OPT can be set to more than one switch group. Previously, it
183 used to be limited to one group of options only.
184 chop()
186 chop(@list) in list context returned the characters chopped in
187 reverse order. This has been reversed to be in the right order.
188 Unicode support
190 Unicode support has seen a large number of incremental
191 improvements, but continues to be highly experimental. It is not
192 expected to be fully supported in the 5.6.x maintenance releases.
193 substr(), join(), repeat(), reverse(), quotemeta() and string
195 concatenation were all handling Unicode strings incorrectly in Perl
196 5.6.0. This has been corrected.
197 Support for "tr///CU" and "tr///UC" etc., have been removed since
199 we realized the interface is broken. For similar functionality,
200 see "pack" in perlfunc.
201 The Unicode Character Database has been updated to version 3.0.1
203 with additions made available to the public as of August 30, 2000.
204 The Unicode character classes \p{Blank} and \p{SpacePerl} have been
206 added. "Blank" is like C isblank(), that is, it contains only
207 "horizontal whitespace" (the space character is, the newline
208 isn't), and the "SpacePerl" is the Unicode equivalent of "\s"
209 (\p{Space} isn't, since that includes the vertical tabulator
210 character, whereas "\s" doesn't.)
211 If you are experimenting with Unicode support in perl, the
213 development versions of Perl may have more to offer. In
214 particular, I/O layers are now available in the development track,
215 but not in the maintenance track, primarily to do backward
216 compatibility issues. Unicode support is also evolving rapidly on
217 a daily basis in the development track--the maintenance track only
218 reflects the most conservative of these changes.
219 64-bit support
221 Support for 64-bit platforms has been improved, but continues to be
222 experimental. The level of support varies greatly among platforms.
223 Compiler
225 The B Compiler and its various backends have had many incremental
226 improvements, but they continue to remain highly experimental. Use
227 in production environments is discouraged.
228 The perlcc tool has been rewritten so that the user interface is
230 much more like that of a C compiler.
231 The perlbc tools has been removed. Use "perlcc -B" instead.
233 Lvalue subroutines
235 There have been various bugfixes to support lvalue subroutines
236 better. However, the feature still remains experimental.
237 IO::Socket
239 IO::Socket::INET failed to open the specified port if the service
240 name was not known. It now correctly uses the supplied port number
241 as is.
242 File::Find
244 File::Find now chdir()s correctly when chasing symbolic links.
245 xsubpp
247 xsubpp now tolerates embedded POD sections.
248 "no Module;"
250 "no Module;" does not produce an error even if Module does not have
251 an unimport() method. This parallels the behavior of "use" vis-a-
252 vis "import".
253 Tests
255 A large number of tests have been added.
256 Core features
258 untie() will now call an UNTIE() hook if it exists. See perltie for
259 details.
260 The "-DT" command line switch outputs copious tokenizing information.
262 See perlrun.
263 Arrays are now always interpolated in double-quotish strings.
265 Previously, "foo@bar.com" used to be a fatal error at compile time, if
266 an array @bar was not used or declared. This transitional behavior was
267 intended to help migrate perl4 code, and is deemed to be no longer
268 useful. See "Arrays now always interpolate into double-quoted
269 strings".
270 keys(), each(), pop(), push(), shift(), splice() and unshift() can all
272 be overridden now.
273 "my __PACKAGE__ $obj" now does the expected thing.
275 Configuration issues
277 On some systems (IRIX and Solaris among them) the system malloc is
278 demonstrably better. While the defaults haven't been changed in order
279 to retain binary compatibility with earlier releases, you may be better
280 off building perl with "Configure -Uusemymalloc ..." as discussed in
281 the INSTALL file.
282 "Configure" has been enhanced in various ways:
284 • Minimizes use of temporary files.
286 • By default, does not link perl with libraries not used by it, such
288 as the various dbm libraries. SunOS 4.x hints preserve behavior on
289 that platform.
290 • Support for pdp11-style memory models has been removed due to
292 obsolescence.
293 • Building outside the source tree is supported on systems that have
295 symbolic links. This is done by running
296 sh /path/to/source/Configure -Dmksymlinks ...
298 make all test install
299 in a directory other than the perl source directory. See INSTALL.
301 • "Configure -S" can be run non-interactively.
303 Documentation
305 README.aix, README.solaris and README.macos have been added.
306 README.posix-bc has been renamed to README.bs2000. These are installed
307 as perlaix, perlsolaris, perlmacos, and perlbs2000 respectively.
308 The following pod documents are brand new:
310 perlclib Internal replacements for standard C library functions
312 perldebtut Perl debugging tutorial
313 perlebcdic Considerations for running Perl on EBCDIC platforms
314 perlnewmod Perl modules: preparing a new module for distribution
315 perlrequick Perl regular expressions quick start
316 perlretut Perl regular expressions tutorial
317 perlutil utilities packaged with the Perl distribution
318 The INSTALL file has been expanded to cover various issues, such as
320 64-bit support.
321 A longer list of contributors has been added to the source
323 distribution. See the file "AUTHORS".
324 Numerous other changes have been made to the included documentation and
326 FAQs.
327 Bundled modules
329 The following modules have been added.
330 B::Concise
332 Walks Perl syntax tree, printing concise info about ops. See
333 B::Concise.
334 File::Temp
336 Returns name and handle of a temporary file safely. See
337 File::Temp.
338 Pod::LaTeX
340 Converts Pod data to formatted LaTeX. See Pod::LaTeX.
341 Pod::Text::Overstrike
343 Converts POD data to formatted overstrike text. See
344 Pod::Text::Overstrike.
345 The following modules have been upgraded.
347 CGI CGI v2.752 is now included.
349 CPAN
351 CPAN v1.59_54 is now included.
352 Class::Struct
354 Various bugfixes have been added.
355 DB_File
357 DB_File v1.75 supports newer Berkeley DB versions, among other
358 improvements.
359 Devel::Peek
361 Devel::Peek has been enhanced to support dumping of memory
362 statistics, when perl is built with the included malloc().
363 File::Find
365 File::Find now supports pre and post-processing of the files in
366 order to sort() them, etc.
367 Getopt::Long
369 Getopt::Long v2.25 is included.
370 IO::Poll
372 Various bug fixes have been included.
373 IPC::Open3
375 IPC::Open3 allows use of numeric file descriptors.
376 Math::BigFloat
378 The fmod() function supports modulus operations. Various bug fixes
379 have also been included.
380 Math::Complex
382 Math::Complex handles inf, NaN etc., better.
383 Net::Ping
385 ping() could fail on odd number of data bytes, and when the echo
386 service isn't running. This has been corrected.
387 Opcode
389 A memory leak has been fixed.
390 Pod::Parser
392 Version 1.13 of the Pod::Parser suite is included.
393 Pod::Text
395 Pod::Text and related modules have been upgraded to the versions in
396 podlators suite v2.08.
397 SDBM_File
399 On dosish platforms, some keys went missing because of lack of
400 support for files with "holes". A workaround for the problem has
401 been added.
402 Sys::Syslog
404 Various bug fixes have been included.
405 Tie::RefHash
407 Now supports Tie::RefHash::Nestable to automagically tie hashref
408 values.
409 Tie::SubstrHash
411 Various bug fixes have been included.
412 Platform-specific improvements
414 The following new ports are now available.
415 NCR MP-RAS
417 NonStop-UX
418 Perl now builds under Amdahl UTS.
420 Perl has also been verified to build under Amiga OS.
422 Support for EPOC has been much improved. See README.epoc.
424 Building perl with -Duseithreads or -Duse5005threads now works under
426 HP-UX 10.20 (previously it only worked under 10.30 or later). You will
427 need a thread library package installed. See README.hpux.
428 Long doubles should now work under Linux.
430 Mac OS Classic is now supported in the mainstream source package. See
432 README.macos.
433 Support for MPE/iX has been updated. See README.mpeix.
435 Support for OS/2 has been improved. See "os2/Changes" and README.os2.
437 Dynamic loading on z/OS (formerly OS/390) has been improved. See
439 README.os390.
440 Support for VMS has seen many incremental improvements, including
442 better support for operators like backticks and system(), and better
443 %ENV handling. See "README.vms" and perlvms.
444 Support for Stratus VOS has been improved. See "vos/Changes" and
446 README.vos.
447 Support for Windows has been improved.
449 • fork() emulation has been improved in various ways, but still
451 continues to be experimental. See perlfork for known bugs and
452 caveats.
453 • %SIG has been enabled under USE_ITHREADS, but its use is completely
455 unsupported under all configurations.
456 • Borland C++ v5.5 is now a supported compiler that can build Perl.
458 However, the generated binaries continue to be incompatible with
459 those generated by the other supported compilers (GCC and Visual
460 C++).
461 • Non-blocking waits for child processes (or pseudo-processes) are
463 supported via "waitpid($pid, &POSIX::WNOHANG)".
464 • A memory leak in accept() has been fixed.
466 • wait(), waitpid() and backticks now return the correct exit status
468 under Windows 9x.
469 • Trailing new %ENV entries weren't propagated to child processes.
471 This is now fixed.
472 • Current directory entries in %ENV are now correctly propagated to
474 child processes.
475 • Duping socket handles with open(F, ">&MYSOCK") now works under
477 Windows 9x.
478 • The makefiles now provide a single switch to bulk-enable all the
480 features enabled in ActiveState ActivePerl (a popular binary
481 distribution).
482 • Win32::GetCwd() correctly returns C:\ instead of C: when at the
484 drive root. Other bugs in chdir() and Cwd::cwd() have also been
485 fixed.
486 • fork() correctly returns undef and sets EAGAIN when it runs out of
488 pseudo-process handles.
489 • ExtUtils::MakeMaker now uses $ENV{LIB} to search for libraries.
491 • UNC path handling is better when perl is built to support fork().
493 • A handle leak in socket handling has been fixed.
495 • send() works from within a pseudo-process.
497 Unless specifically qualified otherwise, the remainder of this document
499 covers changes between the 5.005 and 5.6.0 releases.
500
502 Interpreter cloning, threads, and concurrency
503 Perl 5.6.0 introduces the beginnings of support for running multiple
504 interpreters concurrently in different threads. In conjunction with
505 the perl_clone() API call, which can be used to selectively duplicate
506 the state of any given interpreter, it is possible to compile a piece
507 of code once in an interpreter, clone that interpreter one or more
508 times, and run all the resulting interpreters in distinct threads.
509 On the Windows platform, this feature is used to emulate fork() at the
511 interpreter level. See perlfork for details about that.
512 This feature is still in evolution. It is eventually meant to be used
514 to selectively clone a subroutine and data reachable from that
515 subroutine in a separate interpreter and run the cloned subroutine in a
516 separate thread. Since there is no shared data between the
517 interpreters, little or no locking will be needed (unless parts of the
518 symbol table are explicitly shared). This is obviously intended to be
519 an easy-to-use replacement for the existing threads support.
520 Support for cloning interpreters and interpreter concurrency can be
522 enabled using the -Dusethreads Configure option (see win32/Makefile for
523 how to enable it on Windows.) The resulting perl executable will be
524 functionally identical to one that was built with -Dmultiplicity, but
525 the perl_clone() API call will only be available in the former.
526 -Dusethreads enables the cpp macro USE_ITHREADS by default, which in
528 turn enables Perl source code changes that provide a clear separation
529 between the op tree and the data it operates with. The former is
530 immutable, and can therefore be shared between an interpreter and all
531 of its clones, while the latter is considered local to each
532 interpreter, and is therefore copied for each clone.
533 Note that building Perl with the -Dusemultiplicity Configure option is
535 adequate if you wish to run multiple independent interpreters
536 concurrently in different threads. -Dusethreads only provides the
537 additional functionality of the perl_clone() API call and other support
538 for running cloned interpreters concurrently.
539 NOTE: This is an experimental feature. Implementation details are
541 subject to change.
542 Lexically scoped warning categories
544 You can now control the granularity of warnings emitted by perl at a
545 finer level using the "use warnings" pragma. warnings and perllexwarn
546 have copious documentation on this feature.
547 Unicode and UTF-8 support
549 Perl now uses UTF-8 as its internal representation for character
550 strings. The "utf8" and "bytes" pragmas are used to control this
551 support in the current lexical scope. See perlunicode, utf8 and bytes
552 for more information.
553 This feature is expected to evolve quickly to support some form of I/O
555 disciplines that can be used to specify the kind of input and output
556 data (bytes or characters). Until that happens, additional modules
557 from CPAN will be needed to complete the toolkit for dealing with
558 Unicode.
559 NOTE: This should be considered an experimental feature. Implementation
561 details are subject to change.
562 Support for interpolating named characters
564 The new "\N" escape interpolates named characters within strings. For
565 example, "Hi! \N{WHITE SMILING FACE}" evaluates to a string with a
566 Unicode smiley face at the end.
567 "our" declarations
569 An "our" declaration introduces a value that can be best understood as
570 a lexically scoped symbolic alias to a global variable in the package
571 that was current where the variable was declared. This is mostly
572 useful as an alternative to the "vars" pragma, but also provides the
573 opportunity to introduce typing and other attributes for such
574 variables. See "our" in perlfunc.
575 Support for strings represented as a vector of ordinals
577 Literals of the form "v1.2.3.4" are now parsed as a string composed of
578 characters with the specified ordinals. This is an alternative, more
579 readable way to construct (possibly Unicode) strings instead of
580 interpolating characters, as in "\x{1}\x{2}\x{3}\x{4}". The leading
581 "v" may be omitted if there are more than two ordinals, so 1.2.3 is
582 parsed the same as "v1.2.3".
583 Strings written in this form are also useful to represent version
585 "numbers". It is easy to compare such version "numbers" (which are
586 really just plain strings) using any of the usual string comparison
587 operators "eq", "ne", "lt", "gt", etc., or perform bitwise string
588 operations on them using "|", "&", etc.
589 In conjunction with the new $^V magic variable (which contains the perl
591 version as a string), such literals can be used as a readable way to
592 check if you're running a particular version of Perl:
593 # this will parse in older versions of Perl also
595 if ($^V and $^V gt v5.6.0) {
596 # new features supported
597 }
598 "require" and "use" also have some special magic to support such
600 literals. They will be interpreted as a version rather than as a
601 module name:
602 require v5.6.0; # croak if $^V lt v5.6.0
604 use v5.6.0; # same, but croaks at compile-time
605 Alternatively, the "v" may be omitted if there is more than one dot:
607 require 5.6.0;
609 use 5.6.0;
610 Also, "sprintf" and "printf" support the Perl-specific format flag %v
612 to print ordinals of characters in arbitrary strings:
613 printf "v%vd", $^V; # prints current version, such as "v5.5.650"
615 printf "%*vX", ":", $addr; # formats IPv6 address
616 printf "%*vb", " ", $bits; # displays bitstring
617 See "Scalar value constructors" in perldata for additional information.
619 Improved Perl version numbering system
621 Beginning with Perl version 5.6.0, the version number convention has
622 been changed to a "dotted integer" scheme that is more commonly found
623 in open source projects.
624 Maintenance versions of v5.6.0 will be released as v5.6.1, v5.6.2 etc.
626 The next development series following v5.6.0 will be numbered v5.7.x,
627 beginning with v5.7.0, and the next major production release following
628 v5.6.0 will be v5.8.0.
629 The English module now sets $PERL_VERSION to $^V (a string value)
631 rather than $] (a numeric value). (This is a potential
632 incompatibility. Send us a report via perlbug if you are affected by
633 this.)
634 The v1.2.3 syntax is also now legal in Perl. See "Support for strings
636 represented as a vector of ordinals" for more on that.
637 To cope with the new versioning system's use of at least three
639 significant digits for each version component, the method used for
640 incrementing the subversion number has also changed slightly. We
641 assume that versions older than v5.6.0 have been incrementing the
642 subversion component in multiples of 10. Versions after v5.6.0 will
643 increment them by 1. Thus, using the new notation, 5.005_03 is the
644 "same" as v5.5.30, and the first maintenance version following v5.6.0
645 will be v5.6.1 (which should be read as being equivalent to a floating
646 point value of 5.006_001 in the older format, stored in $]).
647 New syntax for declaring subroutine attributes
649 Formerly, if you wanted to mark a subroutine as being a method call or
650 as requiring an automatic lock() when it is entered, you had to declare
651 that with a "use attrs" pragma in the body of the subroutine. That can
652 now be accomplished with declaration syntax, like this:
653 sub mymethod : locked method;
655 ...
656 sub mymethod : locked method {
657 ...
658 }
659 sub othermethod :locked :method;
661 ...
662 sub othermethod :locked :method {
663 ...
664 }
665 (Note how only the first ":" is mandatory, and whitespace surrounding
667 the ":" is optional.)
668 AutoSplit.pm and SelfLoader.pm have been updated to keep the attributes
670 with the stubs they provide. See attributes.
671 File and directory handles can be autovivified
673 Similar to how constructs such as "$x->[0]" autovivify a reference,
674 handle constructors (open(), opendir(), pipe(), socketpair(),
675 sysopen(), socket(), and accept()) now autovivify a file or directory
676 handle if the handle passed to them is an uninitialized scalar
677 variable. This allows the constructs such as "open(my $fh, ...)" and
678 "open(local $fh,...)" to be used to create filehandles that will
679 conveniently be closed automatically when the scope ends, provided
680 there are no other references to them. This largely eliminates the
681 need for typeglobs when opening filehandles that must be passed around,
682 as in the following example:
683 sub myopen {
685 open my $fh, "@_"
686 or die "Can't open '@_': $!";
687 return $fh;
688 }
689 {
691 my $f = myopen("</etc/motd");
692 print <$f>;
693 # $f implicitly closed here
694 }
695 open() with more than two arguments
697 If open() is passed three arguments instead of two, the second argument
698 is used as the mode and the third argument is taken to be the file
699 name. This is primarily useful for protecting against unintended magic
700 behavior of the traditional two-argument form. See "open" in perlfunc.
701 64-bit support
703 Any platform that has 64-bit integers either
704 (1) natively as longs or ints
706 (2) via special compiler flags
707 (3) using long long or int64_t
708 is able to use "quads" (64-bit integers) as follows:
710 • constants (decimal, hexadecimal, octal, binary) in the code
712 • arguments to oct() and hex()
714 • arguments to print(), printf() and sprintf() (flag prefixes ll, L,
716 q)
717 • printed as such
719 • pack() and unpack() "q" and "Q" formats
721 • in basic arithmetics: + - * / % (NOTE: operating close to the
723 limits of the integer values may produce surprising results)
724 • in bit arithmetics: & | ^ ~ << >> (NOTE: these used to be forced to
726 be 32 bits wide but now operate on the full native width.)
727 • vec()
729 Note that unless you have the case (a) you will have to configure and
731 compile Perl using the -Duse64bitint Configure flag.
732 NOTE: The Configure flags -Duselonglong and -Duse64bits have been
734 deprecated. Use -Duse64bitint instead.
735 There are actually two modes of 64-bitness: the first one is achieved
737 using Configure -Duse64bitint and the second one using Configure
738 -Duse64bitall. The difference is that the first one is minimal and the
739 second one maximal. The first works in more places than the second.
740 The "use64bitint" does only as much as is required to get 64-bit
742 integers into Perl (this may mean, for example, using "long longs")
743 while your memory may still be limited to 2 gigabytes (because your
744 pointers could still be 32-bit). Note that the name "64bitint" does
745 not imply that your C compiler will be using 64-bit "int"s (it might,
746 but it doesn't have to): the "use64bitint" means that you will be able
747 to have 64 bits wide scalar values.
748 The "use64bitall" goes all the way by attempting to switch also
750 integers (if it can), longs (and pointers) to being 64-bit. This may
751 create an even more binary incompatible Perl than -Duse64bitint: the
752 resulting executable may not run at all in a 32-bit box, or you may
753 have to reboot/reconfigure/rebuild your operating system to be 64-bit
754 aware.
755 Natively 64-bit systems like Alpha and Cray need neither -Duse64bitint
757 nor -Duse64bitall.
758 Last but not least: note that due to Perl's habit of always using
760 floating point numbers, the quads are still not true integers. When
761 quads overflow their limits (0...18_446_744_073_709_551_615 unsigned,
762 -9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they
763 are silently promoted to floating point numbers, after which they will
764 start losing precision (in their lower digits).
765 NOTE: 64-bit support is still experimental on most platforms.
767 Existing support only covers the LP64 data model. In particular, the
768 LLP64 data model is not yet supported. 64-bit libraries and system
769 APIs on many platforms have not stabilized--your mileage may vary.
770 Large file support
772 If you have filesystems that support "large files" (files larger than 2
773 gigabytes), you may now also be able to create and access them from
774 Perl.
775 NOTE: The default action is to enable large file support, if
777 available on the platform.
778 If the large file support is on, and you have a Fcntl constant
780 O_LARGEFILE, the O_LARGEFILE is automatically added to the flags of
781 sysopen().
782 Beware that unless your filesystem also supports "sparse files" seeking
784 to umpteen petabytes may be inadvisable.
785 Note that in addition to requiring a proper file system to do large
787 files you may also need to adjust your per-process (or your per-system,
788 or per-process-group, or per-user-group) maximum filesize limits before
789 running Perl scripts that try to handle large files, especially if you
790 intend to write such files.
791 Finally, in addition to your process/process group maximum filesize
793 limits, you may have quota limits on your filesystems that stop you
794 (your user id or your user group id) from using large files.
795 Adjusting your process/user/group/file system/operating system limits
797 is outside the scope of Perl core language. For process limits, you
798 may try increasing the limits using your shell's limits/limit/ulimit
799 command before running Perl. The BSD::Resource extension (not included
800 with the standard Perl distribution) may also be of use, it offers the
801 getrlimit/setrlimit interface that can be used to adjust process
802 resource usage limits, including the maximum filesize limit.
803 Long doubles
805 In some systems you may be able to use long doubles to enhance the
806 range and precision of your double precision floating point numbers
807 (that is, Perl's numbers). Use Configure -Duselongdouble to enable
808 this support (if it is available).
809 "more bits"
811 You can "Configure -Dusemorebits" to turn on both the 64-bit support
812 and the long double support.
813 Enhanced support for sort() subroutines
815 Perl subroutines with a prototype of "($$)", and XSUBs in general, can
816 now be used as sort subroutines. In either case, the two elements to
817 be compared are passed as normal parameters in @_. See "sort" in
818 perlfunc.
819 For unprototyped sort subroutines, the historical behavior of passing
821 the elements to be compared as the global variables $a and $b remains
822 unchanged.
823 "sort $coderef @foo" allowed
825 sort() did not accept a subroutine reference as the comparison function
826 in earlier versions. This is now permitted.
827 File globbing implemented internally
829 Perl now uses the File::Glob implementation of the glob() operator
830 automatically. This avoids using an external csh process and the
831 problems associated with it.
832 NOTE: This is currently an experimental feature. Interfaces and
834 implementation are subject to change.
835 Support for CHECK blocks
837 In addition to "BEGIN", "INIT", "END", "DESTROY" and "AUTOLOAD",
838 subroutines named "CHECK" are now special. These are queued up during
839 compilation and behave similar to END blocks, except they are called at
840 the end of compilation rather than at the end of execution. They
841 cannot be called directly.
842 POSIX character class syntax [: :] supported
844 For example to match alphabetic characters use /[[:alpha:]]/. See
845 perlre for details.
846 Better pseudo-random number generator
848 In 5.005_0x and earlier, perl's rand() function used the C library
849 rand(3) function. As of 5.005_52, Configure tests for drand48(),
850 random(), and rand() (in that order) and picks the first one it finds.
851 These changes should result in better random numbers from rand().
853 Improved "qw//" operator
855 The "qw//" operator is now evaluated at compile time into a true list
856 instead of being replaced with a run time call to "split()". This
857 removes the confusing misbehaviour of "qw//" in scalar context, which
858 had inherited that behaviour from split().
859 Thus:
861 $foo = ($bar) = qw(a b c); print "$foo|$bar\n";
863 now correctly prints "3|a", instead of "2|a".
865 Better worst-case behavior of hashes
867 Small changes in the hashing algorithm have been implemented in order
868 to improve the distribution of lower order bits in the hashed value.
869 This is expected to yield better performance on keys that are repeated
870 sequences.
871 pack() format 'Z' supported
873 The new format type 'Z' is useful for packing and unpacking null-
874 terminated strings. See "pack" in perlfunc.
875 pack() format modifier '!' supported
877 The new format type modifier '!' is useful for packing and unpacking
878 native shorts, ints, and longs. See "pack" in perlfunc.
879 pack() and unpack() support counted strings
881 The template character '/' can be used to specify a counted string type
882 to be packed or unpacked. See "pack" in perlfunc.
883 Comments in pack() templates
885 The '#' character in a template introduces a comment up to end of the
886 line. This facilitates documentation of pack() templates.
887 Weak references
889 In previous versions of Perl, you couldn't cache objects so as to allow
890 them to be deleted if the last reference from outside the cache is
891 deleted. The reference in the cache would hold a reference count on
892 the object and the objects would never be destroyed.
893 Another familiar problem is with circular references. When an object
895 references itself, its reference count would never go down to zero, and
896 it would not get destroyed until the program is about to exit.
897 Weak references solve this by allowing you to "weaken" any reference,
899 that is, make it not count towards the reference count. When the last
900 non-weak reference to an object is deleted, the object is destroyed and
901 all the weak references to the object are automatically undef-ed.
902 To use this feature, you need the Devel::WeakRef package from CPAN,
904 which contains additional documentation.
905 NOTE: This is an experimental feature. Details are subject to change.
907 Binary numbers supported
909 Binary numbers are now supported as literals, in s?printf formats, and
910 "oct()":
911 $answer = 0b101010;
913 printf "The answer is: %b\n", oct("0b101010");
914 Lvalue subroutines
916 Subroutines can now return modifiable lvalues. See "Lvalue
917 subroutines" in perlsub.
918 NOTE: This is an experimental feature. Details are subject to change.
920 Some arrows may be omitted in calls through references
922 Perl now allows the arrow to be omitted in many constructs involving
923 subroutine calls through references. For example, "$foo[10]->('foo')"
924 may now be written "$foo[10]('foo')". This is rather similar to how
925 the arrow may be omitted from "$foo[10]->{'foo'}". Note however, that
926 the arrow is still required for "foo(10)->('bar')".
927 Boolean assignment operators are legal lvalues
929 Constructs such as "($a ||= 2) += 1" are now allowed.
930 exists() is supported on subroutine names
932 The exists() builtin now works on subroutine names. A subroutine is
933 considered to exist if it has been declared (even if implicitly). See
934 "exists" in perlfunc for examples.
935 exists() and delete() are supported on array elements
937 The exists() and delete() builtins now work on simple arrays as well.
938 The behavior is similar to that on hash elements.
939 exists() can be used to check whether an array element has been
941 initialized. This avoids autovivifying array elements that don't
942 exist. If the array is tied, the EXISTS() method in the corresponding
943 tied package will be invoked.
944 delete() may be used to remove an element from the array and return it.
946 The array element at that position returns to its uninitialized state,
947 so that testing for the same element with exists() will return false.
948 If the element happens to be the one at the end, the size of the array
949 also shrinks up to the highest element that tests true for exists(), or
950 0 if none such is found. If the array is tied, the DELETE() method in
951 the corresponding tied package will be invoked.
952 See "exists" in perlfunc and "delete" in perlfunc for examples.
954 Pseudo-hashes work better
956 Dereferencing some types of reference values in a pseudo-hash, such as
957 "$ph->{foo}[1]", was accidentally disallowed. This has been corrected.
958 When applied to a pseudo-hash element, exists() now reports whether the
960 specified value exists, not merely if the key is valid.
961 delete() now works on pseudo-hashes. When given a pseudo-hash element
963 or slice it deletes the values corresponding to the keys (but not the
964 keys themselves). See "Pseudo-hashes: Using an array as a hash" in
965 perlref.
966 Pseudo-hash slices with constant keys are now optimized to array
968 lookups at compile-time.
969 List assignments to pseudo-hash slices are now supported.
971 The "fields" pragma now provides ways to create pseudo-hashes, via
973 fields::new() and fields::phash(). See fields.
974 NOTE: The pseudo-hash data type continues to be experimental.
976 Limiting oneself to the interface elements provided by the
977 fields pragma will provide protection from any future changes.
978 Automatic flushing of output buffers
980 fork(), exec(), system(), qx//, and pipe open()s now flush buffers of
981 all files opened for output when the operation was attempted. This
982 mostly eliminates confusing buffering mishaps suffered by users unaware
983 of how Perl internally handles I/O.
984 This is not supported on some platforms like Solaris where a suitably
986 correct implementation of fflush(NULL) isn't available.
987 Better diagnostics on meaningless filehandle operations
989 Constructs such as "open(<FH>)" and "close(<FH>)" are compile time
990 errors. Attempting to read from filehandles that were opened only for
991 writing will now produce warnings (just as writing to read-only
992 filehandles does).
993 Where possible, buffered data discarded from duped input filehandle
995 "open(NEW, "<&OLD")" now attempts to discard any data that was
996 previously read and buffered in "OLD" before duping the handle. On
997 platforms where doing this is allowed, the next read operation on "NEW"
998 will return the same data as the corresponding operation on "OLD".
999 Formerly, it would have returned the data from the start of the
1000 following disk block instead.
1001 eof() has the same old magic as <>
1003 "eof()" would return true if no attempt to read from "<>" had yet been
1004 made. "eof()" has been changed to have a little magic of its own, it
1005 now opens the "<>" files.
1006 binmode() can be used to set :crlf and :raw modes
1008 binmode() now accepts a second argument that specifies a discipline for
1009 the handle in question. The two pseudo-disciplines ":raw" and ":crlf"
1010 are currently supported on DOS-derivative platforms. See "binmode" in
1011 perlfunc and open.
1012 "-T" filetest recognizes UTF-8 encoded files as "text"
1014 The algorithm used for the "-T" filetest has been enhanced to correctly
1015 identify UTF-8 content as "text".
1016 system(), backticks and pipe open now reflect exec() failure
1018 On Unix and similar platforms, system(), qx() and open(FOO, "cmd |")
1019 etc., are implemented via fork() and exec(). When the underlying
1020 exec() fails, earlier versions did not report the error properly, since
1021 the exec() happened to be in a different process.
1022 The child process now communicates with the parent about the error in
1024 launching the external command, which allows these constructs to return
1025 with their usual error value and set $!.
1026 Improved diagnostics
1028 Line numbers are no longer suppressed (under most likely circumstances)
1029 during the global destruction phase.
1030 Diagnostics emitted from code running in threads other than the main
1032 thread are now accompanied by the thread ID.
1033 Embedded null characters in diagnostics now actually show up. They
1035 used to truncate the message in prior versions.
1036 $foo::a and $foo::b are now exempt from "possible typo" warnings only
1038 if sort() is encountered in package "foo".
1039 Unrecognized alphabetic escapes encountered when parsing quote
1041 constructs now generate a warning, since they may take on new semantics
1042 in later versions of Perl.
1043 Many diagnostics now report the internal operation in which the warning
1045 was provoked, like so:
1046 Use of uninitialized value in concatenation (.) at (eval 1) line 1.
1048 Use of uninitialized value in print at (eval 1) line 1.
1049 Diagnostics that occur within eval may also report the file and line
1051 number where the eval is located, in addition to the eval sequence
1052 number and the line number within the evaluated text itself. For
1053 example:
1054 Not enough arguments for scalar at (eval 4)[newlib/perl5db.pl:1411] line 2, at EOF
1056 Diagnostics follow STDERR
1058 Diagnostic output now goes to whichever file the "STDERR" handle is
1059 pointing at, instead of always going to the underlying C runtime
1060 library's "stderr".
1061 More consistent close-on-exec behavior
1063 On systems that support a close-on-exec flag on filehandles, the flag
1064 is now set for any handles created by pipe(), socketpair(), socket(),
1065 and accept(), if that is warranted by the value of $^F that may be in
1066 effect. Earlier versions neglected to set the flag for handles created
1067 with these operators. See "pipe" in perlfunc, "socketpair" in
1068 perlfunc, "socket" in perlfunc, "accept" in perlfunc, and "$^F" in
1069 perlvar.
1070 syswrite() ease-of-use
1072 The length argument of "syswrite()" has become optional.
1073 Better syntax checks on parenthesized unary operators
1075 Expressions such as:
1076 print defined(&foo,&bar,&baz);
1078 print uc("foo","bar","baz");
1079 undef($foo,&bar);
1080 used to be accidentally allowed in earlier versions, and produced
1082 unpredictable behaviour. Some produced ancillary warnings when used in
1083 this way; others silently did the wrong thing.
1084 The parenthesized forms of most unary operators that expect a single
1086 argument now ensure that they are not called with more than one
1087 argument, making the cases shown above syntax errors. The usual
1088 behaviour of:
1089 print defined &foo, &bar, &baz;
1091 print uc "foo", "bar", "baz";
1092 undef $foo, &bar;
1093 remains unchanged. See perlop.
1095 Bit operators support full native integer width
1097 The bit operators (& | ^ ~ << >>) now operate on the full native
1098 integral width (the exact size of which is available in
1099 $Config{ivsize}). For example, if your platform is either natively
1100 64-bit or if Perl has been configured to use 64-bit integers, these
1101 operations apply to 8 bytes (as opposed to 4 bytes on 32-bit
1102 platforms). For portability, be sure to mask off the excess bits in
1103 the result of unary "~", e.g., "~$x & 0xffffffff".
1104 Improved security features
1106 More potentially unsafe operations taint their results for improved
1107 security.
1108 The "passwd" and "shell" fields returned by the getpwent(), getpwnam(),
1110 and getpwuid() are now tainted, because the user can affect their own
1111 encrypted password and login shell.
1112 The variable modified by shmread(), and messages returned by msgrcv()
1114 (and its object-oriented interface IPC::SysV::Msg::rcv) are also
1115 tainted, because other untrusted processes can modify messages and
1116 shared memory segments for their own nefarious purposes.
1117 More functional bareword prototype (*)
1119 Bareword prototypes have been rationalized to enable them to be used to
1120 override builtins that accept barewords and interpret them in a special
1121 way, such as "require" or "do".
1122 Arguments prototyped as "*" will now be visible within the subroutine
1124 as either a simple scalar or as a reference to a typeglob. See
1125 "Prototypes" in perlsub.
1126 "require" and "do" may be overridden
1128 "require" and "do 'file'" operations may be overridden locally by
1129 importing subroutines of the same name into the current package (or
1130 globally by importing them into the CORE::GLOBAL:: namespace).
1131 Overriding "require" will also affect "use", provided the override is
1132 visible at compile-time. See "Overriding Built-in Functions" in
1133 perlsub.
1134 $^X variables may now have names longer than one character
1136 Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax
1137 error. Now variable names that begin with a control character may be
1138 arbitrarily long. However, for compatibility reasons, these variables
1139 must be written with explicit braces, as "${^XY}" for example.
1140 "${^XYZ}" is synonymous with ${"\cXYZ"}. Variable names with more than
1141 one control character, such as "${^XY^Z}", are illegal.
1142 The old syntax has not changed. As before, `^X' may be either a
1144 literal control-X character or the two-character sequence `caret' plus
1145 `X'. When braces are omitted, the variable name stops after the
1146 control character. Thus "$^XYZ" continues to be synonymous with "$^X .
1147 "YZ"" as before.
1148 As before, lexical variables may not have names beginning with control
1150 characters. As before, variables whose names begin with a control
1151 character are always forced to be in package `main'. All such
1152 variables are reserved for future extensions, except those that begin
1153 with "^_", which may be used by user programs and are guaranteed not to
1154 acquire special meaning in any future version of Perl.
1155 New variable $^C reflects "-c" switch
1157 $^C has a boolean value that reflects whether perl is being run in
1158 compile-only mode (i.e. via the "-c" switch). Since BEGIN blocks are
1159 executed under such conditions, this variable enables perl code to
1160 determine whether actions that make sense only during normal running
1161 are warranted. See perlvar.
1162 New variable $^V contains Perl version as a string
1164 $^V contains the Perl version number as a string composed of characters
1165 whose ordinals match the version numbers, i.e. v5.6.0. This may be
1166 used in string comparisons.
1167 See "Support for strings represented as a vector of ordinals" for an
1169 example.
1170 Optional Y2K warnings
1172 If Perl is built with the cpp macro "PERL_Y2KWARN" defined, it emits
1173 optional warnings when concatenating the number 19 with another number.
1174 This behavior must be specifically enabled when running Configure. See
1176 INSTALL and README.Y2K.
1177 Arrays now always interpolate into double-quoted strings
1179 In double-quoted strings, arrays now interpolate, no matter what. The
1180 behavior in earlier versions of perl 5 was that arrays would
1181 interpolate into strings if the array had been mentioned before the
1182 string was compiled, and otherwise Perl would raise a fatal compile-
1183 time error. In versions 5.000 through 5.003, the error was
1184 Literal @example now requires backslash
1186 In versions 5.004_01 through 5.6.0, the error was
1188 In string, @example now must be written as \@example
1190 The idea here was to get people into the habit of writing
1192 "fred\@example.com" when they wanted a literal "@" sign, just as they
1193 have always written "Give me back my \$5" when they wanted a literal
1194 "$" sign.
1195 Starting with 5.6.1, when Perl now sees an "@" sign in a double-quoted
1197 string, it always attempts to interpolate an array, regardless of
1198 whether or not the array has been used or declared already. The fatal
1199 error has been downgraded to an optional warning:
1200 Possible unintended interpolation of @example in string
1202 This warns you that "fred@example.com" is going to turn into "fred.com"
1204 if you don't backslash the "@". See
1205 http://perl.plover.com/at-error.html for more details about the history
1206 here.
1207 @- and @+ provide starting/ending offsets of regex submatches
1209 The new magic variables @- and @+ provide the starting and ending
1210 offsets, respectively, of $&, $1, $2, etc. See perlvar for details.
1211
1213 Modules
1214 attributes
1215 While used internally by Perl as a pragma, this module also
1216 provides a way to fetch subroutine and variable attributes. See
1217 attributes.
1218 B The Perl Compiler suite has been extensively reworked for this
1220 release. More of the standard Perl test suite passes when run
1221 under the Compiler, but there is still a significant way to go to
1222 achieve production quality compiled executables.
1223 NOTE: The Compiler suite remains highly experimental. The
1225 generated code may not be correct, even when it manages to execute
1226 without errors.
1227 Benchmark
1229 Overall, Benchmark results exhibit lower average error and better
1230 timing accuracy.
1231 You can now run tests for n seconds instead of guessing the right
1233 number of tests to run: e.g., timethese(-5, ...) will run each code
1234 for at least 5 CPU seconds. Zero as the "number of repetitions"
1235 means "for at least 3 CPU seconds". The output format has also
1236 changed. For example:
1237 use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
1239 will now output something like this:
1241 Benchmark: running a, b, each for at least 5 CPU seconds...
1243 a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
1244 b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
1245 New features: "each for at least N CPU seconds...", "wallclock
1247 secs", and the "@ operations/CPU second (n=operations)".
1248 timethese() now returns a reference to a hash of Benchmark objects
1250 containing the test results, keyed on the names of the tests.
1251 timethis() now returns the iterations field in the Benchmark result
1253 object instead of 0.
1254 timethese(), timethis(), and the new cmpthese() (see below) can
1256 also take a format specifier of 'none' to suppress output.
1257 A new function countit() is just like timeit() except that it takes
1259 a TIME instead of a COUNT.
1260 A new function cmpthese() prints a chart comparing the results of
1262 each test returned from a timethese() call. For each possible pair
1263 of tests, the percentage speed difference (iters/sec or
1264 seconds/iter) is shown.
1265 For other details, see Benchmark.
1267 ByteLoader
1269 The ByteLoader is a dedicated extension to generate and run Perl
1270 bytecode. See ByteLoader.
1271 constant
1273 References can now be used.
1274 The new version also allows a leading underscore in constant names,
1276 but disallows a double leading underscore (as in "__LINE__"). Some
1277 other names are disallowed or warned against, including BEGIN, END,
1278 etc. Some names which were forced into main:: used to fail
1279 silently in some cases; now they're fatal (outside of main::) and
1280 an optional warning (inside of main::). The ability to detect
1281 whether a constant had been set with a given name has been added.
1282 See constant.
1284 charnames
1286 This pragma implements the "\N" string escape. See charnames.
1287 Data::Dumper
1289 A "Maxdepth" setting can be specified to avoid venturing too deeply
1290 into deep data structures. See Data::Dumper.
1291 The XSUB implementation of Dump() is now automatically called if
1293 the "Useqq" setting is not in use.
1294 Dumping "qr//" objects works correctly.
1296 DB "DB" is an experimental module that exposes a clean abstraction to
1298 Perl's debugging API.
1299 DB_File
1301 DB_File can now be built with Berkeley DB versions 1, 2 or 3. See
1302 "ext/DB_File/Changes".
1303 Devel::DProf
1305 Devel::DProf, a Perl source code profiler has been added. See
1306 Devel::DProf and dprofpp.
1307 Devel::Peek
1309 The Devel::Peek module provides access to the internal
1310 representation of Perl variables and data. It is a data debugging
1311 tool for the XS programmer.
1312 Dumpvalue
1314 The Dumpvalue module provides screen dumps of Perl data.
1315 DynaLoader
1317 DynaLoader now supports a dl_unload_file() function on platforms
1318 that support unloading shared objects using dlclose().
1319 Perl can also optionally arrange to unload all extension shared
1321 objects loaded by Perl. To enable this, build Perl with the
1322 Configure option "-Accflags=-DDL_UNLOAD_ALL_AT_EXIT". (This maybe
1323 useful if you are using Apache with mod_perl.)
1324 English
1326 $PERL_VERSION now stands for $^V (a string value) rather than for
1327 $] (a numeric value).
1328 Env Env now supports accessing environment variables like PATH as array
1330 variables.
1331 Fcntl
1333 More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for
1334 large file (more than 4GB) access (NOTE: the O_LARGEFILE is
1335 automatically added to sysopen() flags if large file support has
1336 been configured, as is the default), Free/Net/OpenBSD locking
1337 behaviour flags F_FLOCK, F_POSIX, Linux F_SHLCK, and O_ACCMODE: the
1338 combined mask of O_RDONLY, O_WRONLY, and O_RDWR. The
1339 seek()/sysseek() constants SEEK_SET, SEEK_CUR, and SEEK_END are
1340 available via the ":seek" tag. The chmod()/stat() S_IF* constants
1341 and S_IS* functions are available via the ":mode" tag.
1342 File::Compare
1344 A compare_text() function has been added, which allows custom
1345 comparison functions. See File::Compare.
1346 File::Find
1348 File::Find now works correctly when the wanted() function is either
1349 autoloaded or is a symbolic reference.
1350 A bug that caused File::Find to lose track of the working directory
1352 when pruning top-level directories has been fixed.
1353 File::Find now also supports several other options to control its
1355 behavior. It can follow symbolic links if the "follow" option is
1356 specified. Enabling the "no_chdir" option will make File::Find
1357 skip changing the current directory when walking directories. The
1358 "untaint" flag can be useful when running with taint checks
1359 enabled.
1360 See File::Find.
1362 File::Glob
1364 This extension implements BSD-style file globbing. By default, it
1365 will also be used for the internal implementation of the glob()
1366 operator. See File::Glob.
1367 File::Spec
1369 New methods have been added to the File::Spec module: devnull()
1370 returns the name of the null device (/dev/null on Unix) and
1371 tmpdir() the name of the temp directory (normally /tmp on Unix).
1372 There are now also methods to convert between absolute and relative
1373 filenames: abs2rel() and rel2abs(). For compatibility with
1374 operating systems that specify volume names in file paths, the
1375 splitpath(), splitdir(), and catdir() methods have been added.
1376 File::Spec::Functions
1378 The new File::Spec::Functions modules provides a function interface
1379 to the File::Spec module. Allows shorthand
1380 $fullname = catfile($dir1, $dir2, $file);
1382 instead of
1384 $fullname = File::Spec->catfile($dir1, $dir2, $file);
1386 Getopt::Long
1388 Getopt::Long licensing has changed to allow the Perl Artistic
1389 License as well as the GPL. It used to be GPL only, which got in
1390 the way of non-GPL applications that wanted to use Getopt::Long.
1391 Getopt::Long encourages the use of Pod::Usage to produce help
1393 messages. For example:
1394 use Getopt::Long;
1396 use Pod::Usage;
1397 my $man = 0;
1398 my $help = 0;
1399 GetOptions('help|?' => \$help, man => \$man) or pod2usage(2);
1400 pod2usage(1) if $help;
1401 pod2usage(-exitstatus => 0, -verbose => 2) if $man;
1402 __END__
1404 =head1 NAME
1406 sample - Using Getopt::Long and Pod::Usage
1408 =head1 SYNOPSIS
1410 sample [options] [file ...]
1412 Options:
1414 -help brief help message
1415 -man full documentation
1416 =head1 OPTIONS
1418 =over 8
1420 =item B<-help>
1422 Print a brief help message and exits.
1424 =item B<-man>
1426 Prints the manual page and exits.
1428 =back
1430 =head1 DESCRIPTION
1432 B<This program> will read the given input file(s) and do something
1434 useful with the contents thereof.
1435 =cut
1437 See Pod::Usage for details.
1439 A bug that prevented the non-option call-back <> from being
1441 specified as the first argument has been fixed.
1442 To specify the characters < and > as option starters, use ><. Note,
1444 however, that changing option starters is strongly deprecated.
1445 IO write() and syswrite() will now accept a single-argument form of
1447 the call, for consistency with Perl's syswrite().
1448 You can now create a TCP-based IO::Socket::INET without forcing a
1450 connect attempt. This allows you to configure its options (like
1451 making it non-blocking) and then call connect() manually.
1452 A bug that prevented the IO::Socket::protocol() accessor from ever
1454 returning the correct value has been corrected.
1455 IO::Socket::connect now uses non-blocking IO instead of alarm() to
1457 do connect timeouts.
1458 IO::Socket::accept now uses select() instead of alarm() for doing
1460 timeouts.
1461 IO::Socket::INET->new now sets $! correctly on failure. $@ is still
1463 set for backwards compatibility.
1464 JPL Java Perl Lingo is now distributed with Perl. See jpl/README for
1466 more information.
1467 lib "use lib" now weeds out any trailing duplicate entries. "no lib"
1469 removes all named entries.
1470 Math::BigInt
1472 The bitwise operations "<<", ">>", "&", "|", and "~" are now
1473 supported on bigints.
1474 Math::Complex
1476 The accessor methods Re, Im, arg, abs, rho, and theta can now also
1477 act as mutators (accessor $z->Re(), mutator $z->Re(3)).
1478 The class method "display_format" and the corresponding object
1480 method "display_format", in addition to accepting just one
1481 argument, now can also accept a parameter hash. Recognized keys of
1482 a parameter hash are "style", which corresponds to the old one
1483 parameter case, and two new parameters: "format", which is a
1484 printf()-style format string (defaults usually to "%.15g", you can
1485 revert to the default by setting the format string to "undef") used
1486 for both parts of a complex number, and "polar_pretty_print"
1487 (defaults to true), which controls whether an attempt is made to
1488 try to recognize small multiples and rationals of pi (2pi, pi/2) at
1489 the argument (angle) of a polar complex number.
1490 The potentially disruptive change is that in list context both
1492 methods now return the parameter hash, instead of only the value of
1493 the "style" parameter.
1494 Math::Trig
1496 A little bit of radial trigonometry (cylindrical and spherical),
1497 radial coordinate conversions, and the great circle distance were
1498 added.
1499 Pod::Parser, Pod::InputObjects
1501 Pod::Parser is a base class for parsing and selecting sections of
1502 pod documentation from an input stream. This module takes care of
1503 identifying pod paragraphs and commands in the input and hands off
1504 the parsed paragraphs and commands to user-defined methods which
1505 are free to interpret or translate them as they see fit.
1506 Pod::InputObjects defines some input objects needed by Pod::Parser,
1508 and for advanced users of Pod::Parser that need more about a
1509 command besides its name and text.
1510 As of release 5.6.0 of Perl, Pod::Parser is now the officially
1512 sanctioned "base parser code" recommended for use by all pod2xxx
1513 translators. Pod::Text (pod2text) and Pod::Man (pod2man) have
1514 already been converted to use Pod::Parser and efforts to convert
1515 Pod::HTML (pod2html) are already underway. For any questions or
1516 comments about pod parsing and translating issues and utilities,
1517 please use the pod-people@perl.org mailing list.
1518 For further information, please see Pod::Parser and
1520 Pod::InputObjects.
1521 Pod::Checker, podchecker
1523 This utility checks pod files for correct syntax, according to
1524 perlpod. Obvious errors are flagged as such, while warnings are
1525 printed for mistakes that can be handled gracefully. The checklist
1526 is not complete yet. See Pod::Checker.
1527 Pod::ParseUtils, Pod::Find
1529 These modules provide a set of gizmos that are useful mainly for
1530 pod translators. Pod::Find traverses directory structures and
1531 returns found pod files, along with their canonical names (like
1532 "File::Spec::Unix"). Pod::ParseUtils contains Pod::List (useful
1533 for storing pod list information), Pod::Hyperlink (for parsing the
1534 contents of "L<>" sequences) and Pod::Cache (for caching
1535 information about pod files, e.g., link nodes).
1536 Pod::Select, podselect
1538 Pod::Select is a subclass of Pod::Parser which provides a function
1539 named "podselect()" to filter out user-specified sections of raw
1540 pod documentation from an input stream. podselect is a script that
1541 provides access to Pod::Select from other scripts to be used as a
1542 filter. See Pod::Select.
1543 Pod::Usage, pod2usage
1545 Pod::Usage provides the function "pod2usage()" to print usage
1546 messages for a Perl script based on its embedded pod documentation.
1547 The pod2usage() function is generally useful to all script authors
1548 since it lets them write and maintain a single source (the pods)
1549 for documentation, thus removing the need to create and maintain
1550 redundant usage message text consisting of information already in
1551 the pods.
1552 There is also a pod2usage script which can be used from other kinds
1554 of scripts to print usage messages from pods (even for non-Perl
1555 scripts with pods embedded in comments).
1556 For details and examples, please see Pod::Usage.
1558 Pod::Text and Pod::Man
1560 Pod::Text has been rewritten to use Pod::Parser. While pod2text()
1561 is still available for backwards compatibility, the module now has
1562 a new preferred interface. See Pod::Text for the details. The new
1563 Pod::Text module is easily subclassed for tweaks to the output, and
1564 two such subclasses (Pod::Text::Termcap for man-page-style bold and
1565 underlining using termcap information, and Pod::Text::Color for
1566 markup with ANSI color sequences) are now standard.
1567 pod2man has been turned into a module, Pod::Man, which also uses
1569 Pod::Parser. In the process, several outstanding bugs related to
1570 quotes in section headers, quoting of code escapes, and nested
1571 lists have been fixed. pod2man is now a wrapper script around this
1572 module.
1573 SDBM_File
1575 An EXISTS method has been added to this module (and sdbm_exists()
1576 has been added to the underlying sdbm library), so one can now call
1577 exists on an SDBM_File tied hash and get the correct result, rather
1578 than a runtime error.
1579 A bug that may have caused data loss when more than one disk block
1581 happens to be read from the database in a single FETCH() has been
1582 fixed.
1583 Sys::Syslog
1585 Sys::Syslog now uses XSUBs to access facilities from syslog.h so it
1586 no longer requires syslog.ph to exist.
1587 Sys::Hostname
1589 Sys::Hostname now uses XSUBs to call the C library's gethostname()
1590 or uname() if they exist.
1591 Term::ANSIColor
1593 Term::ANSIColor is a very simple module to provide easy and
1594 readable access to the ANSI color and highlighting escape
1595 sequences, supported by most ANSI terminal emulators. It is now
1596 included standard.
1597 Time::Local
1599 The timelocal() and timegm() functions used to silently return
1600 bogus results when the date fell outside the machine's integer
1601 range. They now consistently croak() if the date falls in an
1602 unsupported range.
1603 Win32
1605 The error return value in list context has been changed for all
1606 functions that return a list of values. Previously these functions
1607 returned a list with a single element "undef" if an error occurred.
1608 Now these functions return the empty list in these situations.
1609 This applies to the following functions:
1610 Win32::FsType
1612 Win32::GetOSVersion
1613 The remaining functions are unchanged and continue to return
1615 "undef" on error even in list context.
1616 The Win32::SetLastError(ERROR) function has been added as a
1618 complement to the Win32::GetLastError() function.
1619 The new Win32::GetFullPathName(FILENAME) returns the full absolute
1621 pathname for FILENAME in scalar context. In list context it
1622 returns a two-element list containing the fully qualified directory
1623 name and the filename. See Win32.
1624 XSLoader
1626 The XSLoader extension is a simpler alternative to DynaLoader. See
1627 XSLoader.
1628 DBM Filters
1630 A new feature called "DBM Filters" has been added to all the DBM
1631 modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File.
1632 DBM Filters add four new methods to each DBM module:
1633 filter_store_key
1635 filter_store_value
1636 filter_fetch_key
1637 filter_fetch_value
1638 These can be used to filter key-value pairs before the pairs are
1640 written to the database or just after they are read from the
1641 database. See perldbmfilter for further information.
1642 Pragmata
1644 "use attrs" is now obsolete, and is only provided for backward-
1645 compatibility. It's been replaced by the "sub : attributes" syntax.
1646 See "Subroutine Attributes" in perlsub and attributes.
1647 Lexical warnings pragma, "use warnings;", to control optional warnings.
1649 See perllexwarn.
1650 "use filetest" to control the behaviour of filetests ("-r" "-w" ...).
1652 Currently only one subpragma implemented, "use filetest 'access';",
1653 that uses access(2) or equivalent to check permissions instead of using
1654 stat(2) as usual. This matters in filesystems where there are ACLs
1655 (access control lists): the stat(2) might lie, but access(2) knows
1656 better.
1657 The "open" pragma can be used to specify default disciplines for handle
1659 constructors (e.g. open()) and for qx//. The two pseudo-disciplines
1660 ":raw" and ":crlf" are currently supported on DOS-derivative platforms
1661 (i.e. where binmode is not a no-op). See also "binmode() can be used
1662 to set :crlf and :raw modes".
1663
1665 dprofpp
1666 "dprofpp" is used to display profile data generated using
1667 "Devel::DProf". See dprofpp.
1668 find2perl
1670 The "find2perl" utility now uses the enhanced features of the
1671 File::Find module. The -depth and -follow options are supported. Pod
1672 documentation is also included in the script.
1673 h2xs
1675 The "h2xs" tool can now work in conjunction with "C::Scan" (available
1676 from CPAN) to automatically parse real-life header files. The "-M",
1677 "-a", "-k", and "-o" options are new.
1678 perlcc
1680 "perlcc" now supports the C and Bytecode backends. By default, it
1681 generates output from the simple C backend rather than the optimized C
1682 backend.
1683 Support for non-Unix platforms has been improved.
1685 perldoc
1687 "perldoc" has been reworked to avoid possible security holes. It will
1688 not by default let itself be run as the superuser, but you may still
1689 use the -U switch to try to make it drop privileges first.
1690 The Perl Debugger
1692 Many bug fixes and enhancements were added to perl5db.pl, the Perl
1693 debugger. The help documentation was rearranged. New commands include
1694 "< ?", "> ?", and "{ ?" to list out current actions, "man docpage" to
1695 run your doc viewer on some perl docset, and support for quoted
1696 options. The help information was rearranged, and should be viewable
1697 once again if you're using less as your pager. A serious security hole
1698 was plugged--you should immediately remove all older versions of the
1699 Perl debugger as installed in previous releases, all the way back to
1700 perl3, from your system to avoid being bitten by this.
1701
1703 Many of the platform-specific README files are now part of the perl
1704 installation. See perl for the complete list.
1705 perlapi.pod
1707 The official list of public Perl API functions.
1708 perlboot.pod
1710 A tutorial for beginners on object-oriented Perl.
1711 perlcompile.pod
1713 An introduction to using the Perl Compiler suite.
1714 perldbmfilter.pod
1716 A howto document on using the DBM filter facility.
1717 perldebug.pod
1719 All material unrelated to running the Perl debugger, plus all low-
1720 level guts-like details that risked crushing the casual user of the
1721 debugger, have been relocated from the old manpage to the next
1722 entry below.
1723 perldebguts.pod
1725 This new manpage contains excessively low-level material not
1726 related to the Perl debugger, but slightly related to debugging
1727 Perl itself. It also contains some arcane internal details of how
1728 the debugging process works that may only be of interest to
1729 developers of Perl debuggers.
1730 perlfork.pod
1732 Notes on the fork() emulation currently available for the Windows
1733 platform.
1734 perlfilter.pod
1736 An introduction to writing Perl source filters.
1737 perlhack.pod
1739 Some guidelines for hacking the Perl source code.
1740 perlintern.pod
1742 A list of internal functions in the Perl source code. (List is
1743 currently empty.)
1744 perllexwarn.pod
1746 Introduction and reference information about lexically scoped
1747 warning categories.
1748 perlnumber.pod
1750 Detailed information about numbers as they are represented in Perl.
1751 perlopentut.pod
1753 A tutorial on using open() effectively.
1754 perlreftut.pod
1756 A tutorial that introduces the essentials of references.
1757 perltootc.pod
1759 A tutorial on managing class data for object modules.
1760 perltodo.pod
1762 Discussion of the most often wanted features that may someday be
1763 supported in Perl.
1764 perlunicode.pod
1766 An introduction to Unicode support features in Perl.
1767
1769 Simple sort() using { $a <=> $b } and the like are optimized
1770 Many common sort() operations using a simple inlined block are now
1771 optimized for faster performance.
1772 Optimized assignments to lexical variables
1774 Certain operations in the RHS of assignment statements have been
1775 optimized to directly set the lexical variable on the LHS, eliminating
1776 redundant copying overheads.
1777 Faster subroutine calls
1779 Minor changes in how subroutine calls are handled internally provide
1780 marginal improvements in performance.
1781 delete(), each(), values() and hash iteration are faster
1783 The hash values returned by delete(), each(), values() and hashes in a
1784 list context are the actual values in the hash, instead of copies.
1785 This results in significantly better performance, because it eliminates
1786 needless copying in most situations.
1787
1789 -Dusethreads means something different
1790 The -Dusethreads flag now enables the experimental interpreter-based
1791 thread support by default. To get the flavor of experimental threads
1792 that was in 5.005 instead, you need to run Configure with "-Dusethreads
1793 -Duse5005threads".
1794 As of v5.6.0, interpreter-threads support is still lacking a way to
1796 create new threads from Perl (i.e., "use Thread;" will not work with
1797 interpreter threads). "use Thread;" continues to be available when you
1798 specify the -Duse5005threads option to Configure, bugs and all.
1799 NOTE: Support for threads continues to be an experimental feature.
1801 Interfaces and implementation are subject to sudden and drastic changes.
1802 New Configure flags
1804 The following new flags may be enabled on the Configure command line by
1805 running Configure with "-Dflag".
1806 usemultiplicity
1808 usethreads useithreads (new interpreter threads: no Perl API yet)
1809 usethreads use5005threads (threads as they were in 5.005)
1810 use64bitint (equal to now deprecated 'use64bits')
1812 use64bitall
1813 uselongdouble
1815 usemorebits
1816 uselargefiles
1817 usesocks (only SOCKS v5 supported)
1818 Threadedness and 64-bitness now more daring
1820 The Configure options enabling the use of threads and the use of
1821 64-bitness are now more daring in the sense that they no more have an
1822 explicit list of operating systems of known threads/64-bit
1823 capabilities. In other words: if your operating system has the
1824 necessary APIs and datatypes, you should be able just to go ahead and
1825 use them, for threads by Configure -Dusethreads, and for 64 bits either
1826 explicitly by Configure -Duse64bitint or implicitly if your system has
1827 64-bit wide datatypes. See also "64-bit support".
1828 Long Doubles
1830 Some platforms have "long doubles", floating point numbers of even
1831 larger range than ordinary "doubles". To enable using long doubles for
1832 Perl's scalars, use -Duselongdouble.
1833 -Dusemorebits
1835 You can enable both -Duse64bitint and -Duselongdouble with
1836 -Dusemorebits. See also "64-bit support".
1837 -Duselargefiles
1839 Some platforms support system APIs that are capable of handling large
1840 files (typically, files larger than two gigabytes). Perl will try to
1841 use these APIs if you ask for -Duselargefiles.
1842 See "Large file support" for more information.
1844 installusrbinperl
1846 You can use "Configure -Uinstallusrbinperl" which causes installperl to
1847 skip installing perl also as /usr/bin/perl. This is useful if you
1848 prefer not to modify /usr/bin for some reason or another but harmful
1849 because many scripts assume to find Perl in /usr/bin/perl.
1850 SOCKS support
1852 You can use "Configure -Dusesocks" which causes Perl to probe for the
1853 SOCKS proxy protocol library (v5, not v4). For more information on
1854 SOCKS, see:
1855 http://www.socks.nec.com/
1857 "-A" flag
1859 You can "post-edit" the Configure variables using the Configure "-A"
1860 switch. The editing happens immediately after the platform specific
1861 hints files have been processed but before the actual configuration
1862 process starts. Run "Configure -h" to find out the full "-A" syntax.
1863 Enhanced Installation Directories
1865 The installation structure has been enriched to improve the support for
1866 maintaining multiple versions of perl, to provide locations for vendor-
1867 supplied modules, scripts, and manpages, and to ease maintenance of
1868 locally-added modules, scripts, and manpages. See the section on
1869 Installation Directories in the INSTALL file for complete details. For
1870 most users building and installing from source, the defaults should be
1871 fine.
1872 If you previously used "Configure -Dsitelib" or "-Dsitearch" to set
1874 special values for library directories, you might wish to consider
1875 using the new "-Dsiteprefix" setting instead. Also, if you wish to re-
1876 use a config.sh file from an earlier version of perl, you should be
1877 sure to check that Configure makes sensible choices for the new
1878 directories. See INSTALL for complete details.
1879 gcc automatically tried if 'cc' does not seem to be working
1881 In many platforms the vendor-supplied 'cc' is too stripped-down to
1882 build Perl (basically, the 'cc' doesn't do ANSI C). If this seems to
1883 be the case and the 'cc' does not seem to be the GNU C compiler 'gcc',
1884 an automatic attempt is made to find and use 'gcc' instead.
1885
1887 Supported platforms
1888 • The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the
1889 Thread extension.
1890 • GNU/Hurd is now supported.
1892 • Rhapsody/Darwin is now supported.
1894 • EPOC is now supported (on Psion 5).
1896 • The cygwin port (formerly cygwin32) has been greatly improved.
1898 DOS
1900 • Perl now works with djgpp 2.02 (and 2.03 alpha).
1901 • Environment variable names are not converted to uppercase any more.
1903 • Incorrect exit codes from backticks have been fixed.
1905 • This port continues to use its own builtin globbing (not
1907 File::Glob).
1908 OS390 (OpenEdition MVS)
1910 Support for this EBCDIC platform has not been renewed in this release.
1911 There are difficulties in reconciling Perl's standardization on UTF-8
1912 as its internal representation for characters with the EBCDIC character
1913 set, because the two are incompatible.
1914 It is unclear whether future versions will renew support for this
1916 platform, but the possibility exists.
1917 VMS
1919 Numerous revisions and extensions to configuration, build, testing, and
1920 installation process to accommodate core changes and VMS-specific
1921 options.
1922 Expand %ENV-handling code to allow runtime mapping to logical names,
1924 CLI symbols, and CRTL environ array.
1925 Extension of subprocess invocation code to accept filespecs as command
1927 "verbs".
1928 Add to Perl command line processing the ability to use default file
1930 types and to recognize Unix-style "2>&1".
1931 Expansion of File::Spec::VMS routines, and integration into
1933 ExtUtils::MM_VMS.
1934 Extension of ExtUtils::MM_VMS to handle complex extensions more
1936 flexibly.
1937 Barewords at start of Unix-syntax paths may be treated as text rather
1939 than only as logical names.
1940 Optional secure translation of several logical names used internally by
1942 Perl.
1943 Miscellaneous bugfixing and porting of new core code to VMS.
1945 Thanks are gladly extended to the many people who have contributed VMS
1947 patches, testing, and ideas.
1948 Win32
1950 Perl can now emulate fork() internally, using multiple interpreters
1951 running in different concurrent threads. This support must be enabled
1952 at build time. See perlfork for detailed information.
1953 When given a pathname that consists only of a drivename, such as "A:",
1955 opendir() and stat() now use the current working directory for the
1956 drive rather than the drive root.
1957 The builtin XSUB functions in the Win32:: namespace are documented.
1959 See Win32.
1960 $^X now contains the full path name of the running executable.
1962 A Win32::GetLongPathName() function is provided to complement
1964 Win32::GetFullPathName() and Win32::GetShortPathName(). See Win32.
1965 POSIX::uname() is supported.
1967 system(1,...) now returns true process IDs rather than process handles.
1969 kill() accepts any real process id, rather than strictly return values
1970 from system(1,...).
1971 For better compatibility with Unix, "kill(0, $pid)" can now be used to
1973 test whether a process exists.
1974 The "Shell" module is supported.
1976 Better support for building Perl under command.com in Windows 95 has
1978 been added.
1979 Scripts are read in binary mode by default to allow ByteLoader (and the
1981 filter mechanism in general) to work properly. For compatibility, the
1982 DATA filehandle will be set to text mode if a carriage return is
1983 detected at the end of the line containing the __END__ or __DATA__
1984 token; if not, the DATA filehandle will be left open in binary mode.
1985 Earlier versions always opened the DATA filehandle in text mode.
1986 The glob() operator is implemented via the "File::Glob" extension,
1988 which supports glob syntax of the C shell. This increases the
1989 flexibility of the glob() operator, but there may be compatibility
1990 issues for programs that relied on the older globbing syntax. If you
1991 want to preserve compatibility with the older syntax, you might want to
1992 run perl with "-MFile::DosGlob". For details and compatibility
1993 information, see File::Glob.
1994
1996 <HANDLE> on empty files
1997 With $/ set to "undef", "slurping" an empty file returns a string of
1998 zero length (instead of "undef", as it used to) the first time the
1999 HANDLE is read after $/ is set to "undef". Further reads yield
2000 "undef".
2001 This means that the following will append "foo" to an empty file (it
2003 used to do nothing):
2004 perl -0777 -pi -e 's/^/foo/' empty_file
2006 The behaviour of:
2008 perl -pi -e 's/^/foo/' empty_file
2010 is unchanged (it continues to leave the file empty).
2012 "eval '...'" improvements
2014 Line numbers (as reflected by caller() and most diagnostics) within
2015 "eval '...'" were often incorrect where here documents were involved.
2016 This has been corrected.
2017 Lexical lookups for variables appearing in "eval '...'" within
2019 functions that were themselves called within an "eval '...'" were
2020 searching the wrong place for lexicals. The lexical search now
2021 correctly ends at the subroutine's block boundary.
2022 The use of "return" within "eval {...}" caused $@ not to be reset
2024 correctly when no exception occurred within the eval. This has been
2025 fixed.
2026 Parsing of here documents used to be flawed when they appeared as the
2028 replacement expression in "eval 's/.../.../e'". This has been fixed.
2029 All compilation errors are true errors
2031 Some "errors" encountered at compile time were by necessity generated
2032 as warnings followed by eventual termination of the program. This
2033 enabled more such errors to be reported in a single run, rather than
2034 causing a hard stop at the first error that was encountered.
2035 The mechanism for reporting such errors has been reimplemented to queue
2037 compile-time errors and report them at the end of the compilation as
2038 true errors rather than as warnings. This fixes cases where error
2039 messages leaked through in the form of warnings when code was compiled
2040 at run time using "eval STRING", and also allows such errors to be
2041 reliably trapped using "eval "..."".
2042 Implicitly closed filehandles are safer
2044 Sometimes implicitly closed filehandles (as when they are localized,
2045 and Perl automatically closes them on exiting the scope) could
2046 inadvertently set $? or $!. This has been corrected.
2047 Behavior of list slices is more consistent
2049 When taking a slice of a literal list (as opposed to a slice of an
2050 array or hash), Perl used to return an empty list if the result
2051 happened to be composed of all undef values.
2052 The new behavior is to produce an empty list if (and only if) the
2054 original list was empty. Consider the following example:
2055 @a = (1,undef,undef,2)[2,1,2];
2057 The old behavior would have resulted in @a having no elements. The new
2059 behavior ensures it has three undefined elements.
2060 Note in particular that the behavior of slices of the following cases
2062 remains unchanged:
2063 @a = ()[1,2];
2065 @a = (getpwent)[7,0];
2066 @a = (anything_returning_empty_list())[2,1,2];
2067 @a = @b[2,1,2];
2068 @a = @c{'a','b','c'};
2069 See perldata.
2071 "(\$)" prototype and $foo{a}
2073 A scalar reference prototype now correctly allows a hash or array
2074 element in that slot.
2075 "goto &sub" and AUTOLOAD
2077 The "goto &sub" construct works correctly when &sub happens to be
2078 autoloaded.
2079 "-bareword" allowed under "use integer"
2081 The autoquoting of barewords preceded by "-" did not work in prior
2082 versions when the "integer" pragma was enabled. This has been fixed.
2083 Failures in DESTROY()
2085 When code in a destructor threw an exception, it went unnoticed in
2086 earlier versions of Perl, unless someone happened to be looking in $@
2087 just after the point the destructor happened to run. Such failures are
2088 now visible as warnings when warnings are enabled.
2089 Locale bugs fixed
2091 printf() and sprintf() previously reset the numeric locale back to the
2092 default "C" locale. This has been fixed.
2093 Numbers formatted according to the local numeric locale (such as using
2095 a decimal comma instead of a decimal dot) caused "isn't numeric"
2096 warnings, even while the operations accessing those numbers produced
2097 correct results. These warnings have been discontinued.
2098 Memory leaks
2100 The "eval 'return sub {...}'" construct could sometimes leak memory.
2101 This has been fixed.
2102 Operations that aren't filehandle constructors used to leak memory when
2104 used on invalid filehandles. This has been fixed.
2105 Constructs that modified @_ could fail to deallocate values in @_ and
2107 thus leak memory. This has been corrected.
2108 Spurious subroutine stubs after failed subroutine calls
2110 Perl could sometimes create empty subroutine stubs when a subroutine
2111 was not found in the package. Such cases stopped later method lookups
2112 from progressing into base packages. This has been corrected.
2113 Taint failures under "-U"
2115 When running in unsafe mode, taint violations could sometimes cause
2116 silent failures. This has been fixed.
2117 END blocks and the "-c" switch
2119 Prior versions used to run BEGIN and END blocks when Perl was run in
2120 compile-only mode. Since this is typically not the expected behavior,
2121 END blocks are not executed anymore when the "-c" switch is used, or if
2122 compilation fails.
2123 See "Support for CHECK blocks" for how to run things when the compile
2125 phase ends.
2126 Potential to leak DATA filehandles
2128 Using the "__DATA__" token creates an implicit filehandle to the file
2129 that contains the token. It is the program's responsibility to close
2130 it when it is done reading from it.
2131 This caveat is now better explained in the documentation. See
2133 perldata.
2134
2136 "%s" variable %s masks earlier declaration in same %s
2137 (W misc) A "my" or "our" variable has been redeclared in the
2138 current scope or statement, effectively eliminating all access to
2139 the previous instance. This is almost always a typographical
2140 error. Note that the earlier variable will still exist until the
2141 end of the scope or until all closure referents to it are
2142 destroyed.
2143 "my sub" not yet implemented
2145 (F) Lexically scoped subroutines are not yet implemented. Don't
2146 try that yet.
2147 "our" variable %s redeclared
2149 (W misc) You seem to have already declared the same global once
2150 before in the current lexical scope.
2151 '!' allowed only after types %s
2153 (F) The '!' is allowed in pack() and unpack() only after certain
2154 types. See "pack" in perlfunc.
2155 / cannot take a count
2157 (F) You had an unpack template indicating a counted-length string,
2158 but you have also specified an explicit size for the string. See
2159 "pack" in perlfunc.
2160 / must be followed by a, A or Z
2162 (F) You had an unpack template indicating a counted-length string,
2163 which must be followed by one of the letters a, A or Z to indicate
2164 what sort of string is to be unpacked. See "pack" in perlfunc.
2165 / must be followed by a*, A* or Z*
2167 (F) You had a pack template indicating a counted-length string,
2168 Currently the only things that can have their length counted are
2169 a*, A* or Z*. See "pack" in perlfunc.
2170 / must follow a numeric type
2172 (F) You had an unpack template that contained a '#', but this did
2173 not follow some numeric unpack specification. See "pack" in
2174 perlfunc.
2175 /%s/: Unrecognized escape \\%c passed through
2177 (W regexp) You used a backslash-character combination which is not
2178 recognized by Perl. This combination appears in an interpolated
2179 variable or a "'"-delimited regular expression. The character was
2180 understood literally.
2181 /%s/: Unrecognized escape \\%c in character class passed through
2183 (W regexp) You used a backslash-character combination which is not
2184 recognized by Perl inside character classes. The character was
2185 understood literally.
2186 /%s/ should probably be written as "%s"
2188 (W syntax) You have used a pattern where Perl expected to find a
2189 string, as in the first argument to "join". Perl will treat the
2190 true or false result of matching the pattern against $_ as the
2191 string, which is probably not what you had in mind.
2192 %s() called too early to check prototype
2194 (W prototype) You've called a function that has a prototype before
2195 the parser saw a definition or declaration for it, and Perl could
2196 not check that the call conforms to the prototype. You need to
2197 either add an early prototype declaration for the subroutine in
2198 question, or move the subroutine definition ahead of the call to
2199 get proper prototype checking. Alternatively, if you are certain
2200 that you're calling the function correctly, you may put an
2201 ampersand before the name to avoid the warning. See perlsub.
2202 %s argument is not a HASH or ARRAY element
2204 (F) The argument to exists() must be a hash or array element, such
2205 as:
2206 $foo{$bar}
2208 $ref->{"susie"}[12]
2209 %s argument is not a HASH or ARRAY element or slice
2211 (F) The argument to delete() must be either a hash or array
2212 element, such as:
2213 $foo{$bar}
2215 $ref->{"susie"}[12]
2216 or a hash or array slice, such as:
2218 @foo[$bar, $baz, $xyzzy]
2220 @{$ref->[12]}{"susie", "queue"}
2221 %s argument is not a subroutine name
2223 (F) The argument to exists() for "exists &sub" must be a subroutine
2224 name, and not a subroutine call. "exists &sub()" will generate
2225 this error.
2226 %s package attribute may clash with future reserved word: %s
2228 (W reserved) A lowercase attribute name was used that had a
2229 package-specific handler. That name might have a meaning to Perl
2230 itself some day, even though it doesn't yet. Perhaps you should
2231 use a mixed-case attribute name, instead. See attributes.
2232 (in cleanup) %s
2234 (W misc) This prefix usually indicates that a DESTROY() method
2235 raised the indicated exception. Since destructors are usually
2236 called by the system at arbitrary points during execution, and
2237 often a vast number of times, the warning is issued only once for
2238 any number of failures that would otherwise result in the same
2239 message being repeated.
2240 Failure of user callbacks dispatched using the "G_KEEPERR" flag
2242 could also result in this warning. See "G_KEEPERR" in perlcall.
2243 <> should be quotes
2245 (F) You wrote "require <file>" when you should have written
2246 "require 'file'".
2247 Attempt to join self
2249 (F) You tried to join a thread from within itself, which is an
2250 impossible task. You may be joining the wrong thread, or you may
2251 need to move the join() to some other thread.
2252 Bad evalled substitution pattern
2254 (F) You've used the /e switch to evaluate the replacement for a
2255 substitution, but perl found a syntax error in the code to
2256 evaluate, most likely an unexpected right brace '}'.
2257 Bad realloc() ignored
2259 (S) An internal routine called realloc() on something that had
2260 never been malloc()ed in the first place. Mandatory, but can be
2261 disabled by setting environment variable "PERL_BADFREE" to 1.
2262 Bareword found in conditional
2264 (W bareword) The compiler found a bareword where it expected a
2265 conditional, which often indicates that an || or && was parsed as
2266 part of the last argument of the previous construct, for example:
2267 open FOO || die;
2269 It may also indicate a misspelled constant that has been
2271 interpreted as a bareword:
2272 use constant TYPO => 1;
2274 if (TYOP) { print "foo" }
2275 The "strict" pragma is useful in avoiding such errors.
2277 Binary number > 0b11111111111111111111111111111111 non-portable
2279 (W portable) The binary number you specified is larger than 2**32-1
2280 (4294967295) and therefore non-portable between systems. See
2281 perlport for more on portability concerns.
2282 Bit vector size > 32 non-portable
2284 (W portable) Using bit vector sizes larger than 32 is non-portable.
2285 Buffer overflow in prime_env_iter: %s
2287 (W internal) A warning peculiar to VMS. While Perl was preparing
2288 to iterate over %ENV, it encountered a logical name or symbol
2289 definition which was too long, so it was truncated to the string
2290 shown.
2291 Can't check filesystem of script "%s"
2293 (P) For some reason you can't check the filesystem of the script
2294 for nosuid.
2295 Can't declare class for non-scalar %s in "%s"
2297 (S) Currently, only scalar variables can declared with a specific
2298 class qualifier in a "my" or "our" declaration. The semantics may
2299 be extended for other types of variables in future.
2300 Can't declare %s in "%s"
2302 (F) Only scalar, array, and hash variables may be declared as "my"
2303 or "our" variables. They must have ordinary identifiers as names.
2304 Can't ignore signal CHLD, forcing to default
2306 (W signal) Perl has detected that it is being run with the SIGCHLD
2307 signal (sometimes known as SIGCLD) disabled. Since disabling this
2308 signal will interfere with proper determination of exit status of
2309 child processes, Perl has reset the signal to its default value.
2310 This situation typically indicates that the parent program under
2311 which Perl may be running (e.g., cron) is being very careless.
2312 Can't modify non-lvalue subroutine call
2314 (F) Subroutines meant to be used in lvalue context should be
2315 declared as such, see "Lvalue subroutines" in perlsub.
2316 Can't read CRTL environ
2318 (S) A warning peculiar to VMS. Perl tried to read an element of
2319 %ENV from the CRTL's internal environment array and discovered the
2320 array was missing. You need to figure out where your CRTL
2321 misplaced its environ or define PERL_ENV_TABLES (see perlvms) so
2322 that environ is not searched.
2323 Can't remove %s: %s, skipping file
2325 (S) You requested an inplace edit without creating a backup file.
2326 Perl was unable to remove the original file to replace it with the
2327 modified file. The file was left unmodified.
2328 Can't return %s from lvalue subroutine
2330 (F) Perl detected an attempt to return illegal lvalues (such as
2331 temporary or readonly values) from a subroutine used as an lvalue.
2332 This is not allowed.
2333 Can't weaken a nonreference
2335 (F) You attempted to weaken something that was not a reference.
2336 Only references can be weakened.
2337 Character class [:%s:] unknown
2339 (F) The class in the character class [: :] syntax is unknown. See
2340 perlre.
2341 Character class syntax [%s] belongs inside character classes
2343 (W unsafe) The character class constructs [: :], [= =], and [. .]
2344 go inside character classes, the [] are part of the construct, for
2345 example: /[012[:alpha:]345]/. Note that [= =] and [. .] are not
2346 currently implemented; they are simply placeholders for future
2347 extensions.
2348 Constant is not %s reference
2350 (F) A constant value (perhaps declared using the "use constant"
2351 pragma) is being dereferenced, but it amounts to the wrong type of
2352 reference. The message indicates the type of reference that was
2353 expected. This usually indicates a syntax error in dereferencing
2354 the constant value. See "Constant Functions" in perlsub and
2355 constant.
2356 constant(%s): %s
2358 (F) The parser found inconsistencies either while attempting to
2359 define an overloaded constant, or when trying to find the character
2360 name specified in the "\N{...}" escape. Perhaps you forgot to load
2361 the corresponding "overload" or "charnames" pragma? See charnames
2362 and overload.
2363 CORE::%s is not a keyword
2365 (F) The CORE:: namespace is reserved for Perl keywords.
2366 defined(@array) is deprecated
2368 (D) defined() is not usually useful on arrays because it checks for
2369 an undefined scalar value. If you want to see if the array is
2370 empty, just use "if (@array) { # not empty }" for example.
2371 defined(%hash) is deprecated
2373 (D) defined() is not usually useful on hashes because it checks for
2374 an undefined scalar value. If you want to see if the hash is
2375 empty, just use "if (%hash) { # not empty }" for example.
2376 Did not produce a valid header
2378 See Server error.
2379 (Did you mean "local" instead of "our"?)
2381 (W misc) Remember that "our" does not localize the declared global
2382 variable. You have declared it again in the same lexical scope,
2383 which seems superfluous.
2384 Document contains no data
2386 See Server error.
2387 entering effective %s failed
2389 (F) While under the "use filetest" pragma, switching the real and
2390 effective uids or gids failed.
2391 false [] range "%s" in regexp
2393 (W regexp) A character class range must start and end at a literal
2394 character, not another character class like "\d" or "[:alpha:]".
2395 The "-" in your false range is interpreted as a literal "-".
2396 Consider quoting the "-", "\-". See perlre.
2397 Filehandle %s opened only for output
2399 (W io) You tried to read from a filehandle opened only for writing.
2400 If you intended it to be a read/write filehandle, you needed to
2401 open it with "+<" or "+>" or "+>>" instead of with "<" or nothing.
2402 If you intended only to read from the file, use "<". See "open" in
2403 perlfunc.
2404 flock() on closed filehandle %s
2406 (W closed) The filehandle you're attempting to flock() got itself
2407 closed some time before now. Check your logic flow. flock()
2408 operates on filehandles. Are you attempting to call flock() on a
2409 dirhandle by the same name?
2410 Global symbol "%s" requires explicit package name
2412 (F) You've said "use strict vars", which indicates that all
2413 variables must either be lexically scoped (using "my"), declared
2414 beforehand using "our", or explicitly qualified to say which
2415 package the global variable is in (using "::").
2416 Hexadecimal number > 0xffffffff non-portable
2418 (W portable) The hexadecimal number you specified is larger than
2419 2**32-1 (4294967295) and therefore non-portable between systems.
2420 See perlport for more on portability concerns.
2421 Ill-formed CRTL environ value "%s"
2423 (W internal) A warning peculiar to VMS. Perl tried to read the
2424 CRTL's internal environ array, and encountered an element without
2425 the "=" delimiter used to separate keys from values. The element
2426 is ignored.
2427 Ill-formed message in prime_env_iter: |%s|
2429 (W internal) A warning peculiar to VMS. Perl tried to read a
2430 logical name or CLI symbol definition when preparing to iterate
2431 over %ENV, and didn't see the expected delimiter between key and
2432 value, so the line was ignored.
2433 Illegal binary digit %s
2435 (F) You used a digit other than 0 or 1 in a binary number.
2436 Illegal binary digit %s ignored
2438 (W digit) You may have tried to use a digit other than 0 or 1 in a
2439 binary number. Interpretation of the binary number stopped before
2440 the offending digit.
2441 Illegal number of bits in vec
2443 (F) The number of bits in vec() (the third argument) must be a
2444 power of two from 1 to 32 (or 64, if your platform supports that).
2445 Integer overflow in %s number
2447 (W overflow) The hexadecimal, octal or binary number you have
2448 specified either as a literal or as an argument to hex() or oct()
2449 is too big for your architecture, and has been converted to a
2450 floating point number. On a 32-bit architecture the largest
2451 hexadecimal, octal or binary number representable without overflow
2452 is 0xFFFFFFFF, 037777777777, or 0b11111111111111111111111111111111
2453 respectively. Note that Perl transparently promotes all numbers to
2454 a floating point representation internally--subject to loss of
2455 precision errors in subsequent operations.
2456 Invalid %s attribute: %s
2458 The indicated attribute for a subroutine or variable was not
2459 recognized by Perl or by a user-supplied handler. See attributes.
2460 Invalid %s attributes: %s
2462 The indicated attributes for a subroutine or variable were not
2463 recognized by Perl or by a user-supplied handler. See attributes.
2464 invalid [] range "%s" in regexp
2466 The offending range is now explicitly displayed.
2467 Invalid separator character %s in attribute list
2469 (F) Something other than a colon or whitespace was seen between the
2470 elements of an attribute list. If the previous attribute had a
2471 parenthesised parameter list, perhaps that list was terminated too
2472 soon. See attributes.
2473 Invalid separator character %s in subroutine attribute list
2475 (F) Something other than a colon or whitespace was seen between the
2476 elements of a subroutine attribute list. If the previous attribute
2477 had a parenthesised parameter list, perhaps that list was
2478 terminated too soon.
2479 leaving effective %s failed
2481 (F) While under the "use filetest" pragma, switching the real and
2482 effective uids or gids failed.
2483 Lvalue subs returning %s not implemented yet
2485 (F) Due to limitations in the current implementation, array and
2486 hash values cannot be returned in subroutines used in lvalue
2487 context. See "Lvalue subroutines" in perlsub.
2488 Method %s not permitted
2490 See Server error.
2491 Missing %sbrace%s on \N{}
2493 (F) Wrong syntax of character name literal "\N{charname}" within
2494 double-quotish context.
2495 Missing command in piped open
2497 (W pipe) You used the "open(FH, "| command")" or "open(FH, "command
2498 |")" construction, but the command was missing or blank.
2499 Missing name in "my sub"
2501 (F) The reserved syntax for lexically scoped subroutines requires
2502 that they have a name with which they can be found.
2503 No %s specified for -%c
2505 (F) The indicated command line switch needs a mandatory argument,
2506 but you haven't specified one.
2507 No package name allowed for variable %s in "our"
2509 (F) Fully qualified variable names are not allowed in "our"
2510 declarations, because that doesn't make much sense under existing
2511 semantics. Such syntax is reserved for future extensions.
2512 No space allowed after -%c
2514 (F) The argument to the indicated command line switch must follow
2515 immediately after the switch, without intervening spaces.
2516 no UTC offset information; assuming local time is UTC
2518 (S) A warning peculiar to VMS. Perl was unable to find the local
2519 timezone offset, so it's assuming that local system time is
2520 equivalent to UTC. If it's not, define the logical name
2521 SYS$TIMEZONE_DIFFERENTIAL to translate to the number of seconds
2522 which need to be added to UTC to get local time.
2523 Octal number > 037777777777 non-portable
2525 (W portable) The octal number you specified is larger than 2**32-1
2526 (4294967295) and therefore non-portable between systems. See
2527 perlport for more on portability concerns.
2528 See also perlport for writing portable code.
2530 panic: del_backref
2532 (P) Failed an internal consistency check while trying to reset a
2533 weak reference.
2534 panic: kid popen errno read
2536 (F) forked child returned an incomprehensible message about its
2537 errno.
2538 panic: magic_killbackrefs
2540 (P) Failed an internal consistency check while trying to reset all
2541 weak references to an object.
2542 Parentheses missing around "%s" list
2544 (W parenthesis) You said something like
2545 my $foo, $bar = @_;
2547 when you meant
2549 my ($foo, $bar) = @_;
2551 Remember that "my", "our", and "local" bind tighter than comma.
2553 Possible unintended interpolation of %s in string
2555 (W ambiguous) It used to be that Perl would try to guess whether
2556 you wanted an array interpolated or a literal @. It no longer does
2557 this; arrays are now always interpolated into strings. This means
2558 that if you try something like:
2559 print "fred@example.com";
2561 and the array @example doesn't exist, Perl is going to print
2563 "fred.com", which is probably not what you wanted. To get a
2564 literal "@" sign in a string, put a backslash before it, just as
2565 you would to get a literal "$" sign.
2566 Possible Y2K bug: %s
2568 (W y2k) You are concatenating the number 19 with another number,
2569 which could be a potential Year 2000 problem.
2570 pragma "attrs" is deprecated, use "sub NAME : ATTRS" instead
2572 (W deprecated) You have written something like this:
2573 sub doit
2575 {
2576 use attrs qw(locked);
2577 }
2578 You should use the new declaration syntax instead.
2580 sub doit : locked
2582 {
2583 ...
2584 The "use attrs" pragma is now obsolete, and is only provided for
2586 backward-compatibility. See "Subroutine Attributes" in perlsub.
2587 Premature end of script headers
2589 See Server error.
2590 Repeat count in pack overflows
2592 (F) You can't specify a repeat count so large that it overflows
2593 your signed integers. See "pack" in perlfunc.
2594 Repeat count in unpack overflows
2596 (F) You can't specify a repeat count so large that it overflows
2597 your signed integers. See "unpack" in perlfunc.
2598 realloc() of freed memory ignored
2600 (S) An internal routine called realloc() on something that had
2601 already been freed.
2602 Reference is already weak
2604 (W misc) You have attempted to weaken a reference that is already
2605 weak. Doing so has no effect.
2606 setpgrp can't take arguments
2608 (F) Your system has the setpgrp() from BSD 4.2, which takes no
2609 arguments, unlike POSIX setpgid(), which takes a process ID and
2610 process group ID.
2611 Strange *+?{} on zero-length expression
2613 (W regexp) You applied a regular expression quantifier in a place
2614 where it makes no sense, such as on a zero-width assertion. Try
2615 putting the quantifier inside the assertion instead. For example,
2616 the way to match "abc" provided that it is followed by three
2617 repetitions of "xyz" is "/abc(?=(?:xyz){3})/", not
2618 "/abc(?=xyz){3}/".
2619 switching effective %s is not implemented
2621 (F) While under the "use filetest" pragma, we cannot switch the
2622 real and effective uids or gids.
2623 This Perl can't reset CRTL environ elements (%s)
2625 This Perl can't set CRTL environ elements (%s=%s)
2626 (W internal) Warnings peculiar to VMS. You tried to change or
2627 delete an element of the CRTL's internal environ array, but your
2628 copy of Perl wasn't built with a CRTL that contained the setenv()
2629 function. You'll need to rebuild Perl with a CRTL that does, or
2630 redefine PERL_ENV_TABLES (see perlvms) so that the environ array
2631 isn't the target of the change to %ENV which produced the warning.
2632 Too late to run %s block
2634 (W void) A CHECK or INIT block is being defined during run time
2635 proper, when the opportunity to run them has already passed.
2636 Perhaps you are loading a file with "require" or "do" when you
2637 should be using "use" instead. Or perhaps you should put the
2638 "require" or "do" inside a BEGIN block.
2639 Unknown open() mode '%s'
2641 (F) The second argument of 3-argument open() is not among the list
2642 of valid modes: "<", ">", ">>", "+<", "+>", "+>>", "-|", "|-".
2643 Unknown process %x sent message to prime_env_iter: %s
2645 (P) An error peculiar to VMS. Perl was reading values for %ENV
2646 before iterating over it, and someone else stuck a message in the
2647 stream of data Perl expected. Someone's very confused, or perhaps
2648 trying to subvert Perl's population of %ENV for nefarious purposes.
2649 Unrecognized escape \\%c passed through
2651 (W misc) You used a backslash-character combination which is not
2652 recognized by Perl. The character was understood literally.
2653 Unterminated attribute parameter in attribute list
2655 (F) The lexer saw an opening (left) parenthesis character while
2656 parsing an attribute list, but the matching closing (right)
2657 parenthesis character was not found. You may need to add (or
2658 remove) a backslash character to get your parentheses to balance.
2659 See attributes.
2660 Unterminated attribute list
2662 (F) The lexer found something other than a simple identifier at the
2663 start of an attribute, and it wasn't a semicolon or the start of a
2664 block. Perhaps you terminated the parameter list of the previous
2665 attribute too soon. See attributes.
2666 Unterminated attribute parameter in subroutine attribute list
2668 (F) The lexer saw an opening (left) parenthesis character while
2669 parsing a subroutine attribute list, but the matching closing
2670 (right) parenthesis character was not found. You may need to add
2671 (or remove) a backslash character to get your parentheses to
2672 balance.
2673 Unterminated subroutine attribute list
2675 (F) The lexer found something other than a simple identifier at the
2676 start of a subroutine attribute, and it wasn't a semicolon or the
2677 start of a block. Perhaps you terminated the parameter list of the
2678 previous attribute too soon.
2679 Value of CLI symbol "%s" too long
2681 (W misc) A warning peculiar to VMS. Perl tried to read the value
2682 of an %ENV element from a CLI symbol table, and found a resultant
2683 string longer than 1024 characters. The return value has been
2684 truncated to 1024 characters.
2685 Version number must be a constant number
2687 (P) The attempt to translate a "use Module n.n LIST" statement into
2688 its equivalent "BEGIN" block found an internal inconsistency with
2689 the version number.
2690
2692 lib/attrs
2693 Compatibility tests for "sub : attrs" vs the older "use attrs".
2694 lib/env
2696 Tests for new environment scalar capability (e.g., "use Env
2697 qw($BAR);").
2698 lib/env-array
2700 Tests for new environment array capability (e.g., "use Env
2701 qw(@PATH);").
2702 lib/io_const
2704 IO constants (SEEK_*, _IO*).
2705 lib/io_dir
2707 Directory-related IO methods (new, read, close, rewind, tied
2708 delete).
2709 lib/io_multihomed
2711 INET sockets with multi-homed hosts.
2712 lib/io_poll
2714 IO poll().
2715 lib/io_unix
2717 UNIX sockets.
2718 op/attrs
2720 Regression tests for "my ($x,@y,%z) : attrs" and <sub : attrs>.
2721 op/filetest
2723 File test operators.
2724 op/lex_assign
2726 Verify operations that access pad objects (lexicals and
2727 temporaries).
2728 op/exists_sub
2730 Verify "exists &sub" operations.
2731
2733 Perl Source Incompatibilities
2734 Beware that any new warnings that have been added or old ones that have
2735 been enhanced are not considered incompatible changes.
2736 Since all new warnings must be explicitly requested via the "-w" switch
2738 or the "warnings" pragma, it is ultimately the programmer's
2739 responsibility to ensure that warnings are enabled judiciously.
2740 CHECK is a new keyword
2742 All subroutine definitions named CHECK are now special. See
2743 "/"Support for CHECK blocks"" for more information.
2744 Treatment of list slices of undef has changed
2746 There is a potential incompatibility in the behavior of list slices
2747 that are comprised entirely of undefined values. See "Behavior of
2748 list slices is more consistent".
2749 Format of $English::PERL_VERSION is different
2751 The English module now sets $PERL_VERSION to $^V (a string value)
2752 rather than $] (a numeric value). This is a potential
2753 incompatibility. Send us a report via perlbug if you are affected
2754 by this.
2755 See "Improved Perl version numbering system" for the reasons for
2757 this change.
2758 Literals of the form 1.2.3 parse differently
2760 Previously, numeric literals with more than one dot in them were
2761 interpreted as a floating point number concatenated with one or
2762 more numbers. Such "numbers" are now parsed as strings composed of
2763 the specified ordinals.
2764 For example, "print 97.98.99" used to output 97.9899 in earlier
2766 versions, but now prints "abc".
2767 See "Support for strings represented as a vector of ordinals".
2769 Possibly changed pseudo-random number generator
2771 Perl programs that depend on reproducing a specific set of pseudo-
2772 random numbers may now produce different output due to improvements
2773 made to the rand() builtin. You can use "sh Configure
2774 -Drandfunc=rand" to obtain the old behavior.
2775 See "Better pseudo-random number generator".
2777 Hashing function for hash keys has changed
2779 Even though Perl hashes are not order preserving, the apparently
2780 random order encountered when iterating on the contents of a hash
2781 is actually determined by the hashing algorithm used. Improvements
2782 in the algorithm may yield a random order that is different from
2783 that of previous versions, especially when iterating on hashes.
2784 See "Better worst-case behavior of hashes" for additional
2786 information.
2787 "undef" fails on read only values
2789 Using the "undef" operator on a readonly value (such as $1) has the
2790 same effect as assigning "undef" to the readonly value--it throws
2791 an exception.
2792 Close-on-exec bit may be set on pipe and socket handles
2794 Pipe and socket handles are also now subject to the close-on-exec
2795 behavior determined by the special variable $^F.
2796 See "More consistent close-on-exec behavior".
2798 Writing "$$1" to mean "${$}1" is unsupported
2800 Perl 5.004 deprecated the interpretation of $$1 and similar within
2801 interpolated strings to mean "$$ . "1"", but still allowed it.
2802 In Perl 5.6.0 and later, "$$1" always means "${$1}".
2804 delete(), each(), values() and "\(%h)"
2806 operate on aliases to values, not copies
2807 delete(), each(), values() and hashes (e.g. "\(%h)") in a list
2809 context return the actual values in the hash, instead of copies (as
2810 they used to in earlier versions). Typical idioms for using these
2811 constructs copy the returned values, but this can make a
2812 significant difference when creating references to the returned
2813 values. Keys in the hash are still returned as copies when
2814 iterating on a hash.
2815 See also "delete(), each(), values() and hash iteration are
2817 faster".
2818 vec(EXPR,OFFSET,BITS) enforces powers-of-two BITS
2820 vec() generates a run-time error if the BITS argument is not a
2821 valid power-of-two integer.
2822 Text of some diagnostic output has changed
2824 Most references to internal Perl operations in diagnostics have
2825 been changed to be more descriptive. This may be an issue for
2826 programs that may incorrectly rely on the exact text of diagnostics
2827 for proper functioning.
2828 "%@" has been removed
2830 The undocumented special variable "%@" that used to accumulate
2831 "background" errors (such as those that happen in DESTROY()) has
2832 been removed, because it could potentially result in memory leaks.
2833 Parenthesized not() behaves like a list operator
2835 The "not" operator now falls under the "if it looks like a
2836 function, it behaves like a function" rule.
2837 As a result, the parenthesized form can be used with "grep" and
2839 "map". The following construct used to be a syntax error before,
2840 but it works as expected now:
2841 grep not($_), @things;
2843 On the other hand, using "not" with a literal list slice may not
2845 work. The following previously allowed construct:
2846 print not (1,2,3)[0];
2848 needs to be written with additional parentheses now:
2850 print not((1,2,3)[0]);
2852 The behavior remains unaffected when "not" is not followed by
2854 parentheses.
2855 Semantics of bareword prototype "(*)" have changed
2857 The semantics of the bareword prototype "*" have changed. Perl
2858 5.005 always coerced simple scalar arguments to a typeglob, which
2859 wasn't useful in situations where the subroutine must distinguish
2860 between a simple scalar and a typeglob. The new behavior is to not
2861 coerce bareword arguments to a typeglob. The value will always be
2862 visible as either a simple scalar or as a reference to a typeglob.
2863 See "More functional bareword prototype (*)".
2865 Semantics of bit operators may have changed on 64-bit platforms
2867 If your platform is either natively 64-bit or if Perl has been
2868 configured to used 64-bit integers, i.e., $Config{ivsize} is 8,
2869 there may be a potential incompatibility in the behavior of bitwise
2870 numeric operators (& | ^ ~ << >>). These operators used to
2871 strictly operate on the lower 32 bits of integers in previous
2872 versions, but now operate over the entire native integral width.
2873 In particular, note that unary "~" will produce different results
2874 on platforms that have different $Config{ivsize}. For portability,
2875 be sure to mask off the excess bits in the result of unary "~",
2876 e.g., "~$x & 0xffffffff".
2877 See "Bit operators support full native integer width".
2879 More builtins taint their results
2881 As described in "Improved security features", there may be more
2882 sources of taint in a Perl program.
2883 To avoid these new tainting behaviors, you can build Perl with the
2885 Configure option "-Accflags=-DINCOMPLETE_TAINTS". Beware that the
2886 ensuing perl binary may be insecure.
2887 C Source Incompatibilities
2889 "PERL_POLLUTE"
2890 Release 5.005 grandfathered old global symbol names by providing
2891 preprocessor macros for extension source compatibility. As of
2892 release 5.6.0, these preprocessor definitions are not available by
2893 default. You need to explicitly compile perl with "-DPERL_POLLUTE"
2894 to get these definitions. For extensions still using the old
2895 symbols, this option can be specified via MakeMaker:
2896 perl Makefile.PL POLLUTE=1
2898 "PERL_IMPLICIT_CONTEXT"
2900 This new build option provides a set of macros for all API
2901 functions such that an implicit interpreter/thread context argument
2902 is passed to every API function. As a result of this, something
2903 like "sv_setsv(foo,bar)" amounts to a macro invocation that
2904 actually translates to something like
2905 "Perl_sv_setsv(my_perl,foo,bar)". While this is generally expected
2906 to not have any significant source compatibility issues, the
2907 difference between a macro and a real function call will need to be
2908 considered.
2909 This means that there is a source compatibility issue as a result
2911 of this if your extensions attempt to use pointers to any of the
2912 Perl API functions.
2913 Note that the above issue is not relevant to the default build of
2915 Perl, whose interfaces continue to match those of prior versions
2916 (but subject to the other options described here).
2917 See "Background and PERL_IMPLICIT_CONTEXT" in perlguts for detailed
2919 information on the ramifications of building Perl with this option.
2920 NOTE: PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
2922 with one of -Dusethreads, -Dusemultiplicity, or both. It is not
2923 intended to be enabled by users at this time.
2924 "PERL_POLLUTE_MALLOC"
2926 Enabling Perl's malloc in release 5.005 and earlier caused the
2927 namespace of the system's malloc family of functions to be usurped
2928 by the Perl versions, since by default they used the same names.
2929 Besides causing problems on platforms that do not allow these
2930 functions to be cleanly replaced, this also meant that the system
2931 versions could not be called in programs that used Perl's malloc.
2932 Previous versions of Perl have allowed this behaviour to be
2933 suppressed with the HIDEMYMALLOC and EMBEDMYMALLOC preprocessor
2934 definitions.
2935 As of release 5.6.0, Perl's malloc family of functions have default
2937 names distinct from the system versions. You need to explicitly
2938 compile perl with "-DPERL_POLLUTE_MALLOC" to get the older
2939 behaviour. HIDEMYMALLOC and EMBEDMYMALLOC have no effect, since
2940 the behaviour they enabled is now the default.
2941 Note that these functions do not constitute Perl's memory
2943 allocation API. See "Memory Allocation" in perlguts for further
2944 information about that.
2945 Compatible C Source API Changes
2947 "PATCHLEVEL" is now "PERL_VERSION"
2948 The cpp macros "PERL_REVISION", "PERL_VERSION", and
2949 "PERL_SUBVERSION" are now available by default from perl.h, and
2950 reflect the base revision, patchlevel, and subversion respectively.
2951 "PERL_REVISION" had no prior equivalent, while "PERL_VERSION" and
2952 "PERL_SUBVERSION" were previously available as "PATCHLEVEL" and
2953 "SUBVERSION".
2954 The new names cause less pollution of the cpp namespace and reflect
2956 what the numbers have come to stand for in common practice. For
2957 compatibility, the old names are still supported when patchlevel.h
2958 is explicitly included (as required before), so there is no source
2959 incompatibility from the change.
2960 Binary Incompatibilities
2962 In general, the default build of this release is expected to be binary
2963 compatible for extensions built with the 5.005 release or its
2964 maintenance versions. However, specific platforms may have broken
2965 binary compatibility due to changes in the defaults used in hints
2966 files. Therefore, please be sure to always check the platform-specific
2967 README files for any notes to the contrary.
2968 The usethreads or usemultiplicity builds are not binary compatible with
2970 the corresponding builds in 5.005.
2971 On platforms that require an explicit list of exports (AIX, OS/2 and
2973 Windows, among others), purely internal symbols such as parser
2974 functions and the run time opcodes are not exported by default. Perl
2975 5.005 used to export all functions irrespective of whether they were
2976 considered part of the public API or not.
2977 For the full list of public API functions, see perlapi.
2979
2981 Localizing a tied hash element may leak memory
2982 As of the 5.6.1 release, there is a known leak when code such as this
2983 is executed:
2984 use Tie::Hash;
2986 tie my %tie_hash => 'Tie::StdHash';
2987 ...
2989 local($tie_hash{Foo}) = 1; # leaks
2991 Known test failures
2993 • 64-bit builds
2994 Subtest #15 of lib/b.t may fail under 64-bit builds on platforms
2996 such as HP-UX PA64 and Linux IA64. The issue is still being
2997 investigated.
2998 The lib/io_multihomed test may hang in HP-UX if Perl has been
3000 configured to be 64-bit. Because other 64-bit platforms do not
3001 hang in this test, HP-UX is suspect. All other tests pass in
3002 64-bit HP-UX. The test attempts to create and connect to
3003 "multihomed" sockets (sockets which have multiple IP addresses).
3004 Note that 64-bit support is still experimental.
3006 • Failure of Thread tests
3008 The subtests 19 and 20 of lib/thr5005.t test are known to fail due
3010 to fundamental problems in the 5.005 threading implementation.
3011 These are not new failures--Perl 5.005_0x has the same bugs, but
3012 didn't have these tests. (Note that support for 5.005-style
3013 threading remains experimental.)
3014 • NEXTSTEP 3.3 POSIX test failure
3016 In NEXTSTEP 3.3p2 the implementation of the strftime(3) in the
3018 operating system libraries is buggy: the %j format numbers the days
3019 of a month starting from zero, which, while being logical to
3020 programmers, will cause the subtests 19 to 27 of the lib/posix test
3021 may fail.
3022 • Tru64 (aka Digital UNIX, aka DEC OSF/1) lib/sdbm test failure with
3024 gcc
3025 If compiled with gcc 2.95 the lib/sdbm test will fail (dump core).
3027 The cure is to use the vendor cc, it comes with the operating
3028 system and produces good code.
3029 EBCDIC platforms not fully supported
3031 In earlier releases of Perl, EBCDIC environments like OS390 (also known
3032 as Open Edition MVS) and VM-ESA were supported. Due to changes
3033 required by the UTF-8 (Unicode) support, the EBCDIC platforms are not
3034 supported in Perl 5.6.0.
3035 The 5.6.1 release improves support for EBCDIC platforms, but they are
3037 not fully supported yet.
3038 UNICOS/mk CC failures during Configure run
3040 In UNICOS/mk the following errors may appear during the Configure run:
3041 Guessing which symbols your C compiler and preprocessor define...
3043 CC-20 cc: ERROR File = try.c, Line = 3
3044 ...
3045 bad switch yylook 79bad switch yylook 79bad switch yylook 79bad switch yylook 79#ifdef A29K
3046 ...
3047 4 errors detected in the compilation of "try.c".
3048 The culprit is the broken awk of UNICOS/mk. The effect is fortunately
3050 rather mild: Perl itself is not adversely affected by the error, only
3051 the h2ph utility coming with Perl, and that is rather rarely needed
3052 these days.
3053 Arrow operator and arrays
3055 When the left argument to the arrow operator "->" is an array, or the
3056 "scalar" operator operating on an array, the result of the operation
3057 must be considered erroneous. For example:
3058 @x->[2]
3060 scalar(@x)->[2]
3061 These expressions will get run-time errors in some future release of
3063 Perl.
3064 Experimental features
3066 As discussed above, many features are still experimental. Interfaces
3067 and implementation of these features are subject to change, and in
3068 extreme cases, even subject to removal in some future release of Perl.
3069 These features include the following:
3070 Threads
3072 Unicode
3073 64-bit support
3074 Lvalue subroutines
3075 Weak references
3076 The pseudo-hash data type
3077 The Compiler suite
3078 Internal implementation of file globbing
3079 The DB module
3080 The regular expression code constructs:
3081 "(?{ code })" and "(??{ code })"
3082
3084 Character class syntax [: :] is reserved for future extensions
3085 (W) Within regular expression character classes ([]) the syntax
3086 beginning with "[:" and ending with ":]" is reserved for future
3087 extensions. If you need to represent those character sequences
3088 inside a regular expression character class, just quote the square
3089 brackets with the backslash: "\[:" and ":\]".
3090 Ill-formed logical name |%s| in prime_env_iter
3092 (W) A warning peculiar to VMS. A logical name was encountered when
3093 preparing to iterate over %ENV which violates the syntactic rules
3094 governing logical names. Because it cannot be translated normally,
3095 it is skipped, and will not appear in %ENV. This may be a benign
3096 occurrence, as some software packages might directly modify logical
3097 name tables and introduce nonstandard names, or it may indicate
3098 that a logical name table has been corrupted.
3099 In string, @%s now must be written as \@%s
3101 The description of this error used to say:
3102 (Someday it will simply assume that an unbackslashed @
3104 interpolates an array.)
3105 That day has come, and this fatal error has been removed. It has
3107 been replaced by a non-fatal warning instead. See "Arrays now
3108 always interpolate into double-quoted strings" for details.
3109 Probable precedence problem on %s
3111 (W) The compiler found a bareword where it expected a conditional,
3112 which often indicates that an || or && was parsed as part of the
3113 last argument of the previous construct, for example:
3114 open FOO || die;
3116 regexp too big
3118 (F) The current implementation of regular expressions uses shorts
3119 as address offsets within a string. Unfortunately this means that
3120 if the regular expression compiles to longer than 32767, it'll blow
3121 up. Usually when you want a regular expression this big, there is
3122 a better way to do it with multiple statements. See perlre.
3123 Use of "$$<digit>" to mean "${$}<digit>" is deprecated
3125 (D) Perl versions before 5.004 misinterpreted any type marker
3126 followed by "$" and a digit. For example, "$$0" was incorrectly
3127 taken to mean "${$}0" instead of "${$0}". This bug is (mostly)
3128 fixed in Perl 5.004.
3129 However, the developers of Perl 5.004 could not fix this bug
3131 completely, because at least two widely-used modules depend on the
3132 old meaning of "$$0" in a string. So Perl 5.004 still interprets
3133 "$$<digit>" in the old (broken) way inside strings; but it
3134 generates this message as a warning. And in Perl 5.005, this
3135 special treatment will cease.
3136
3138 If you find what you think is a bug, you might check the articles
3139 recently posted to the comp.lang.perl.misc newsgroup. There may also
3140 be information at http://www.perl.com/ , the Perl Home Page.
3141 If you believe you have an unreported bug, please run the perlbug
3143 program included with your release. Be sure to trim your bug down to a
3144 tiny but sufficient test case. Your bug report, along with the output
3145 of "perl -V", will be sent off to perlbug@perl.org to be analysed by
3146 the Perl porting team.
3147
3149 The Changes file for exhaustive details on what changed.
3150 The INSTALL file for how to build Perl.
3152 The README file for general stuff.
3154 The Artistic and Copying files for copyright information.
3156
3158 Written by Gurusamy Sarathy <gsar@ActiveState.com>, with many
3159 contributions from The Perl Porters.
3160 Send omissions or corrections to <perlbug@perl.org>.
3162perl v5.36.3 2023-11-30 PERL561DELTA(1)