3 perldelta - what's new for perl v5.6 (as of v5.005_64)
7 This is an unsupported alpha release, meant for intrepid Perl developers
8 only. The included sources may not even build correctly on some platforms.
9 Subscribing to perl5-porters is the best way to monitor and contribute
10 to the progress of development releases (see www.perl.org for info).
12 This document describes differences between the 5.005 release and this one.
14 =head1 Incompatible Changes
16 =head2 Perl Source Incompatibilities
18 Beware that any new warnings that have been added or old ones
19 that have been enhanced are B<not> considered incompatible changes.
21 Since all new warnings must be explicitly requested via the C<-w>
22 switch or the C<warnings> pragma, it is ultimately the programmer's
23 responsibility to ensure that warnings are enabled judiciously.
27 =item CHECK is a new keyword
29 In addition to C<BEGIN>, C<INIT>, C<END>, C<DESTROY> and C<AUTOLOAD>,
30 subroutines named C<CHECK> are now special. These are queued up during
31 compilation and behave similar to END blocks, except they are called at
32 the end of compilation rather than at the end of execution. They cannot
35 =item Treatment of list slices of undef has changed
37 When taking a slice of a literal list (as opposed to a slice of
38 an array or hash), Perl used to return an empty list if the
39 result happened to be composed of all undef values.
41 The new behavior is to produce an empty list if (and only if)
42 the original list was empty. Consider the following example:
44 @a = (1,undef,undef,2)[2,1,2];
46 The old behavior would have resulted in @a having no elements.
47 The new behavior ensures it has three undefined elements.
49 Note in particular that the behavior of slices of the following
50 cases remains unchanged:
54 @a = (anything_returning_empty_list())[2,1,2];
60 =head2 Perl's version numbering has changed
62 Beginning with Perl version 5.6, the version number convention has been
63 changed to a "dotted integer" scheme that is more commonly found in open
66 Maintenance versions of v5.6.0 will be released as v5.6.1, v5.6.2 etc.
67 The next development series following v5.6 will be numbered v5.7.x,
68 beginning with v5.7.0, and the next major production release following
71 The English module now sets $PERL_VERSION to $^V (a string value) rather
72 than C<$]> (a numeric value). (This is a potential incompatibility.
73 Send us a report via perlbug if you are affected by this.)
75 The v1.2.3 syntax is also now legal in Perl.
76 See L<Support for strings represented as a vector of ordinals> for more on that.
78 To cope with the new versioning system's use of at least three significant
79 digits for each version component, the method used for incrementing the
80 subversion number has also changed slightly. We assume that versions older
81 than v5.6 have been incrementing the subversion component in multiples of
82 10. Versions after v5.6.0 will increment them by 1. Thus, using the new
83 notation, 5.005_03 is the same as v5.5.30, and the first maintenance
84 version following v5.6.0 will be v5.6.1, which amounts to a floating point
87 =item Literals of the form C<1.2.3> parse differently
89 Previously, numeric literals with more than one dot in them were
90 interpreted as a floating point number concatenated with one or more
91 numbers. Such "numbers" are now parsed as strings composed of the
94 For example, C<print 97.98.99> used to output C<97.9899> in earlier
95 versions, but now prints C<abc>.
97 See L<Support for strings represented as a vector of ordinals> below.
99 =item Possibly changed pseudo-random number generator
101 In 5.005_0x and earlier, perl's rand() function used the C library
102 rand(3) function. As of 5.005_52, Configure tests for drand48(),
103 random(), and rand() (in that order) and picks the first one it finds.
104 Perl programs that depend on reproducing a specific set of pseudo-random
105 numbers will now likely produce different output. You can use
106 C<sh Configure -Drandfunc=rand> to obtain the old behavior.
108 =item Hashing function for hash keys has changed
110 Perl hashes are not order preserving. The apparently random order
111 encountered when iterating on the contents of a hash is determined
112 by the hashing algorithm used. To improve the distribution of lower
113 bits in the hashed value, the algorithm has changed slightly as of
114 5.005_52. When iterating over hashes, this may yield a random order
115 that is B<different> from that of previous versions.
117 =item C<undef> fails on read only values
119 Using the C<undef> operator on a readonly value (such as $1) has
120 the same effect as assigning C<undef> to the readonly value--it
123 =item Close-on-exec bit may be set on pipe and socket handles
125 On systems that support a close-on-exec flag on filehandles, the
126 flag will be set for any handles created by pipe(), socketpair(),
127 socket(), and accept(), if that is warranted by the value of $^F
128 that may be in effect. Earlier versions neglected to set the flag
129 for handles created with these operators. See L<perlfunc/pipe>,
130 L<perlfunc/socketpair>, L<perlfunc/socket>, L<perlfunc/accept>,
133 =item Writing C<"$$1"> to mean C<"${$}1"> is unsupported
135 Perl 5.004 deprecated the interpretation of C<$$1> and
136 similar within interpolated strings to mean C<$$ . "1">,
137 but still allowed it.
139 In Perl 5.6 and later, C<"$$1"> always means C<"${$1}">.
141 =item delete(), values() and C<\(%h)> operate on aliases to values, not copies
143 delete(), each(), values() and hashes in a list context return the actual
144 values in the hash, instead of copies (as they used to in earlier
145 versions). Typical idioms for using these constructs copy the
146 returned values, but this can make a significant difference when
147 creating references to the returned values.
149 Keys in the hash are still returned as copies when iterating on
152 =item vec(EXPR,OFFSET,BITS) enforces powers-of-two BITS
154 vec() generates a run-time error if the BITS argument is not
155 a valid power-of-two integer.
157 =item Text of some diagnostic output has changed
159 Most references to internal Perl operations in diagnostics
160 have been changed to be more descriptive. This may be an
161 issue for programs that may incorrectly rely on the exact
162 text of diagnostics for proper functioning.
164 =item C<%@> has been removed
166 The undocumented special variable C<%@> that used to accumulate
167 "background" errors (such as those that happen in DESTROY())
168 has been removed, because it could potentially result in memory
171 =item Parenthesized not() behaves like a list operator
173 The C<not> operator now falls under the "if it looks like a function,
174 it behaves like a function" rule.
176 As a result, the parenthesized form can be used with C<grep> and C<map>.
177 The following construct used to be a syntax error before, but it works
180 grep not($_), @things;
182 On the other hand, using C<not> with a literal list slice may not
183 work. The following previously allowed construct:
185 print not (1,2,3)[0];
187 needs to be written with additional parentheses now:
189 print not((1,2,3)[0]);
191 The behavior remains unaffected when C<not> is not followed by parentheses.
193 =item Semantics of bareword prototype C<(*)> have changed
195 Arguments prototyped as C<*> will now be visible within the subroutine
196 as either a simple scalar or as a reference to a typeglob. Perl 5.005
197 always coerced simple scalar arguments to a typeglob, which wasn't useful
198 in situations where the subroutine must distinguish between a simple
199 scalar and a typeglob. See L<perlsub/Prototypes>.
203 =head2 C Source Incompatibilities
207 =item C<PERL_POLLUTE>
209 Release 5.005 grandfathered old global symbol names by providing preprocessor
210 macros for extension source compatibility. As of release 5.6, these
211 preprocessor definitions are not available by default. You need to explicitly
212 compile perl with C<-DPERL_POLLUTE> to get these definitions. For
213 extensions still using the old symbols, this option can be
214 specified via MakeMaker:
216 perl Makefile.PL POLLUTE=1
218 =item C<PERL_IMPLICIT_CONTEXT>
220 PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
221 with one of -Dusethreads, -Dusemultiplicity, or both. It is not
222 intended to be enabled by users at this time.
224 This new build option provides a set of macros for all API functions
225 such that an implicit interpreter/thread context argument is passed to
226 every API function. As a result of this, something like C<sv_setsv(foo,bar)>
227 amounts to a macro invocation that actually translates to something like
228 C<Perl_sv_setsv(my_perl,foo,bar)>. While this is generally expected
229 to not have any significant source compatibility issues, the difference
230 between a macro and a real function call will need to be considered.
232 This means that there B<is> a source compatibility issue as a result of
233 this if your extensions attempt to use pointers to any of the Perl API
236 Note that the above issue is not relevant to the default build of
237 Perl, whose interfaces continue to match those of prior versions
238 (but subject to the other options described here).
240 See L<perlguts/"The Perl API"> for detailed information on the
241 ramifications of building Perl using this option.
243 =item C<PERL_POLLUTE_MALLOC>
245 Enabling Perl's malloc in release 5.005 and earlier caused
246 the namespace of system versions of the malloc family of functions to
247 be usurped by the Perl versions, since by default they used the
250 Besides causing problems on platforms that do not allow these functions to
251 be cleanly replaced, this also meant that the system versions could not
252 be called in programs that used Perl's malloc. Previous versions of Perl
253 have allowed this behaviour to be suppressed with the HIDEMYMALLOC and
254 EMBEDMYMALLOC preprocessor definitions.
256 As of release 5.6, Perl's malloc family of functions have default names
257 distinct from the system versions. You need to explicitly compile perl with
258 C<-DPERL_POLLUTE_MALLOC> to get the older behaviour. HIDEMYMALLOC
259 and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now
262 Note that these functions do B<not> constitute Perl's memory allocation API.
263 See L<perlguts/"Memory Allocation"> for further information about that.
267 =head2 Compatible C Source API Changes
271 =item C<PATCHLEVEL> is now C<PERL_VERSION>
273 The cpp macros C<PERL_REVISION>, C<PERL_VERSION>, and C<PERL_SUBVERSION>
274 are now available by default from perl.h, and reflect the base revision,
275 patchlevel, and subversion respectively. C<PERL_REVISION> had no
276 prior equivalent, while C<PERL_VERSION> and C<PERL_SUBVERSION> were
277 previously available as C<PATCHLEVEL> and C<SUBVERSION>.
279 The new names cause less pollution of the B<cpp> namespace and reflect what
280 the numbers have come to stand for in common practice. For compatibility,
281 the old names are still supported when F<patchlevel.h> is explicitly
282 included (as required before), so there is no source incompatibility
285 =item Support for C++ exceptions
287 change#3386, also needs perlguts documentation
288 [TODO - Chip Salzenberg <chip@perlsupport.com>]
292 =head2 Binary Incompatibilities
294 In general, the default build of this release is expected to be binary
295 compatible for extensions built with the 5.005 release or its maintenance
296 versions. However, specific platforms may have broken binary compatibility
297 due to changes in the defaults used in hints files. Therefore, please be
298 sure to always check the platform-specific README files for any notes to
301 The usethreads or usemultiplicity builds are B<not> binary compatible
302 with the corresponding builds in 5.005.
304 On platforms that require an explicit list of exports (AIX, OS/2 and Windows,
305 among others), purely internal symbols such as parser functions and the
306 run time opcodes are not exported by default. Perl 5.005 used to export
307 all functions irrespective of whether they were considered part of the
310 For the full list of public API functions, see L<perlapi>.
312 =head1 Installation and Configuration Improvements
314 =head2 -Dusethreads means something different
316 WARNING: Support for threads continues to be an experimental feature.
317 Interfaces and implementation are subject to sudden and drastic changes.
319 The -Dusethreads flag now enables the experimental interpreter-based thread
320 support by default. To get the flavor of experimental threads that was in
321 5.005 instead, you need to ask for -Duse5005threads.
323 As of v5.5.640, interpreter-threads support is still lacking a way to
324 create new threads from Perl (i.e., C<use Thread;> will not work with
325 interpreter threads). C<use Thread;> continues to be available when you
326 ask for -Duse5005threads, bugs and all.
328 =head2 New Configure flags
330 The following new flags may be enabled on the Configure command line
331 by running Configure with C<-Dflag>.
336 use64bitint (equal to now deprecated 'use64bits')
342 usesocks (only SOCKS v5 supported)
344 =head2 Threadedness and 64-bitness now more daring
346 The Configure options enabling the use of threads and the use of
347 64-bitness are now more daring in the sense that they no more have an
348 explicit list of operating systems of known threads/64-bit
349 capabilities. In other words: if your operating system has the
350 necessary APIs and datatypes, you should be able just to go ahead and
351 use them, for threads by Configure -Dusethreads, and for 64 bits
352 either explicitly by Configure -Duse64bitint or implicitly if your
353 system has 64 bit wide datatypes. See also L<"64-bit support">.
357 Some platforms have "long doubles", floating point numbers of even
358 larger range than ordinary "doubles". To enable using long doubles for
359 Perl's scalars, use -Duselongdouble.
363 You can enable both -Duse64bitint and -Dlongdouble by -Dusemorebits.
364 See also L<"64-bit support">.
366 =head2 -Duselargefiles
368 Some platforms support large files, files larger than two gigabytes.
369 See L<"Large file support"> for more information.
371 =head2 installusrbinperl
373 You can use "Configure -Uinstallusrbinperl" which causes installperl
374 to skip installing perl also as /usr/bin/perl. This is useful if you
375 prefer not to modify /usr/bin for some reason or another but harmful
376 because many scripts assume to find Perl in /usr/bin/perl.
380 You can use "Configure -Dusesocks" which causes Perl to probe
381 for the SOCKS (v5, not v4) proxy protocol library,
382 http://www.socks.nec.com/
386 You can "post-edit" the Configure variables using the Configure C<-A>
387 flag. The editing happens immediately after the platform specific
388 hints files have been processed but before the actual configuration
389 process starts. Run C<Configure -h> to find out the full C<-A> syntax.
391 =head2 Enhanced Installation Directories
393 The installation structure has been enriched to improve the support
394 for maintaining multiple versions of perl, to provide locations for
395 vendor-supplied modules, scripts, and manpages, and to ease maintenance
396 of locally-added modules, scripts, and manpages. See the section on
397 Installation Directories in the INSTALL file for complete details.
398 For most users building and installing from source, the defaults should
401 If you previously used C<Configure -Dsitelib> or C<-Dsitearch> to set
402 special values for library directories, you might wish to consider using
403 the new C<-Dsiteprefix> setting instead. Also, if you wish to re-use a
404 config.sh file from an earlier version of perl, you should be sure to
405 check that Configure makes sensible choices for the new directories.
406 See INSTALL for complete details.
410 =head2 Unicode and UTF-8 support
412 Perl can optionally use UTF-8 as its internal representation for character
413 strings. The C<utf8> and C<bytes> pragmas are used to control this support
414 in the current lexical scope. See L<perlunicode>, L<utf8> and L<bytes> for
417 =head2 Interpreter cloning, threads, and concurrency
419 WARNING: This is an experimental feature in a pre-alpha state. Use
422 Perl 5.005_63 introduces the beginnings of support for running multiple
423 interpreters concurrently in different threads. In conjunction with
424 the perl_clone() API call, which can be used to selectively duplicate
425 the state of any given interpreter, it is possible to compile a
426 piece of code once in an interpreter, clone that interpreter
427 one or more times, and run all the resulting interpreters in distinct
430 On Windows, this feature is used to emulate fork() at the interpreter
431 level. See L<perlfork>.
433 This feature is still in evolution. It is eventually meant to be used
434 to selectively clone a subroutine and data reachable from that
435 subroutine in a separate interpreter and run the cloned subroutine
436 in a separate thread. Since there is no shared data between the
437 interpreters, little or no locking will be needed (unless parts of
438 the symbol table are explicitly shared). This is obviously intended
439 to be an easy-to-use replacement for the existing threads support.
441 Support for cloning interpreters and interpreter concurrency can be
442 enabled using the -Dusethreads Configure option (see win32/Makefile for
443 how to enable it on Windows.) The resulting perl executable will be
444 functionally identical to one that was built with -Dmultiplicity, but
445 the perl_clone() API call will only be available in the former.
447 -Dusethreads enables, the cpp macros USE_ITHREADS by default, which enables
448 Perl source code changes that provide a clear separation between the op tree
449 and the data it operates with. The former is considered immutable, and can
450 therefore be shared between an interpreter and all of its clones, while the
451 latter is considered local to each interpreter, and is therefore copied for
454 Note that building Perl with the -Dusemultiplicity Configure option
455 is adequate if you wish to run multiple B<independent> interpreters
456 concurrently in different threads. -Dusethreads only provides the
457 additional functionality of the perl_clone() API call and other
458 support for running B<cloned> interpreters concurrently.
460 [XXX TODO - the Compiler backends may be broken when USE_ITHREADS is
463 =head2 Lexically scoped warning categories
465 You can now control the granularity of warnings emitted by perl at a finer
466 level using the C<use warnings> pragma. See L<warnings> and L<perllexwarn>
469 =head2 Lvalue subroutines
471 WARNING: This is an experimental feature.
474 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>,
475 Tuomas Lukka <lukka@iki.fi>)]
477 =head2 "our" declarations
479 An "our" declaration introduces a value that can be best understood
480 as a lexically scoped symbolic alias to a global variable in the
481 package that was current where the variable was declared. This is
482 mostly useful as an alternative to the C<vars> pragma, but also provides
483 the opportunity to introduce typing and other attributes for such
484 variables. See L<perlfunc/our>.
486 =head2 Support for strings represented as a vector of ordinals
488 Literals of the form C<v1.2.3.4> are now parsed as a string composed of
489 of characters with the specified ordinals. This is an alternative, more
490 readable way to construct (possibly unicode) strings instead of
491 interpolating characters, as in C<"\x{1}\x{2}\x{3}\x{4}">. The leading
492 C<v> may be omitted if there are more than two ordinals, so C<1.2.3> is
493 parsed the same as C<v1.2.3>.
495 Strings written in this form are also useful to represent version "numbers".
496 It is easy to compare such version "numbers" (which are really just plain
497 strings) using any of the usual string comparison operators C<eq>, C<ne>,
498 C<lt>, C<gt>, etc., or perform bitwise string operations on them using C<|>,
501 In conjunction with the new C<$^V> magic variable (which contains
502 the perl version as a string), such literals can be used as a readable way
503 to check if you're running a particular version of Perl:
505 # this will parse in older versions of Perl also
506 if ($^V and $^V gt v5.5.640) {
507 # new features supported
510 C<require> and C<use> also have some special magic to support such literals.
511 They will be interpreted as a version rather than as a module name:
513 require v5.6.0; # croak if $^V lt v5.6.0
514 use v5.6.0; # same, but croaks at compile-time
516 Alternatively, the C<v> may be omitted if there is more than one dot:
521 Also, C<sprintf> and C<printf> support the Perl-specific format flag C<%v>
522 to print ordinals of characters in arbitrary strings:
524 printf "v%vd", $^V; # prints current version, such as "v5.5.650"
525 printf "%*vX", ":", $addr; # formats IPv6 address
526 printf "%*vb", " ", $bits; # displays bitstring
528 See L<perlop/"Strings of Character"> for additional information.
530 =head2 Weak references
532 WARNING: This is an experimental feature.
534 In previous versions of Perl, you couldn't cache objects so as
535 to allow them to be deleted if the last reference from outside
536 the cache is deleted. The reference in the cache would hold a
537 reference count on the object and the objects would never be
540 Another familiar problem is with circular references. When an
541 object references itself, its reference count would never go
542 down to zero, and it would not get destroyed until the program
545 Weak references solve this by allowing you to "weaken" any
546 reference, that is, make it not count towards the reference count.
547 When the last non-weak reference to an object is deleted, the object
548 is destroyed and all the weak references to the object are
549 automatically undef-ed.
551 To use this feature, you need the WeakRef package from CPAN, which
552 contains additional documentation.
554 change#3385, also need perlguts documentation
555 [TODO - Tuomas Lukka <lukka@iki.fi>]
557 =head2 File globbing implemented internally
559 WARNING: This is currently an experimental feature. Interfaces and
560 implementation are likely to change.
562 Perl now uses the File::Glob implementation of the glob() operator
563 automatically. This avoids using an external csh process and the
564 problems associated with it.
566 =head2 Binary numbers supported
568 Binary numbers are now supported as literals, in s?printf formats, and
572 printf "The answer is: %b\n", oct("0b101010");
574 =head2 Some arrows may be omitted in calls through references
576 Perl now allows the arrow to be omitted in many constructs
577 involving subroutine calls through references. For example,
578 C<$foo[10]-E<gt>('foo')> may now be written C<$foo[10]('foo')>.
579 This is rather similar to how the arrow may be omitted from
580 C<$foo[10]-E<gt>{'foo'}>. Note however, that the arrow is still
581 required for C<foo(10)-E<gt>('bar')>.
583 =head2 exists() is supported on subroutine names
585 The exists() builtin now works on subroutine names. A subroutine
586 is considered to exist if it has been declared (even if implicitly).
587 See L<perlfunc/exists> for examples.
589 =head2 exists() and delete() are supported on array elements
591 The exists() and delete() builtins now work on simple arrays as well.
592 The behavior is similar to that on hash elements.
594 exists() can be used to check whether an array element has been
595 initialized. This avoids autovivifying array elements that don't exist.
596 If the array is tied, the EXISTS() method in the corresponding tied
597 package will be invoked.
599 delete() may be used to remove an element from the array and return
600 it. The array element at that position returns to its unintialized
601 state, so that testing for the same element with exists() will return
602 false. If the element happens to be the one at the end, the size of
603 the array also shrinks up to the highest element that tests true for
604 exists(), or 0 if none such is found. If the array is tied, the DELETE()
605 method in the corresponding tied package will be invoked.
607 See L<perlfunc/exists> and L<perlfunc/delete> for examples.
609 =head2 syswrite() ease-of-use
611 The length argument of C<syswrite()> has become optional.
613 =head2 File and directory handles can be autovivified
615 Similar to how constructs such as C<$x-E<gt>[0]> autovivify a reference,
616 handle constructors (open(), opendir(), pipe(), socketpair(), sysopen(),
617 socket(), and accept()) now autovivify a file or directory handle
618 if the handle passed to them is an uninitialized scalar variable. This
619 allows the constructs such as C<open(my $fh, ...)> and C<open(local $fh,...)>
620 to be used to create filehandles that will conveniently be closed
621 automatically when the scope ends, provided there are no other references
622 to them. This largely eliminates the need for typeglobs when opening
623 filehandles that must be passed around, as in the following example:
627 or die "Can't open '@_': $!";
632 my $f = myopen("</etc/motd");
634 # $f implicitly closed here
637 [TODO - this idiom needs more pod penetration]
639 =head2 64-bit support
641 NOTE: The Configure flags -Duselonglong and -Duse64bits
642 have been deprecated. Use -Duse64bitint instead.
644 Any platform that has 64-bit integers either (a) natively as longs or
645 ints (b) via special compiler flags (c) using long long are able to
646 use "quads" (64-integers) as follows:
652 constants (decimal, hexadecimal, octal, binary) in the code
656 arguments to oct() and hex()
660 arguments to print(), printf() and sprintf() (flag prefixes ll, L, q)
668 pack() and unpack() "q" and "Q" formats
672 in basic arithmetics: + - * / %
676 vec() (but see the below note about bit arithmetics)
680 Note that unless you have the case (a) you will have to configure
681 and compile Perl using the -Duse64bitint Configure flag.
683 Unfortunately bit arithmetics (&, |, ^, ~, <<, >>) for numbers are not
684 64-bit clean, they are explictly forced to be 32-bit because of
685 tangled backward compatibility issues. This limitation is subject to
686 change. Bit arithmetics for bit vector scalars (created by vec()) are
687 not limited in their width, you can use the & | ^ ~ operators on such
690 There are actually two modes of 64-bitness: the first one is achieved
691 using Configure -Duse64bitint and the second one using Configure
692 -Duse64bitall. The difference is that the first one is minimal and
693 the second one maximal. The first one does only as much as is
694 required to get 64-bit integers into Perl (this may mean, for example,
695 using "long longs") while your memory may still be limited to 2
696 gigabytes (because your pointers most likely are 32-bit); the second
697 one goes all the way by attempting to switch also longs (and pointers)
698 being 64-bit. This may create an even more binary incompatible Perl
699 than -Duse64bitint: the resulting executable may not run at all in a
700 CPU-bit box, or you may have to reboot/reconfigure/rebuild your
701 operating system to be 64-bit aware.
703 Natively 64-bit systems like Alpha and Cray need neither -Duse64bitint
706 Last but not least: note that due to Perl's habit of always using
707 floating point numbers the quads are still not true integers.
708 When quads overflow their limits (0...18_446_744_073_709_551_615 unsigned,
709 -9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they
710 are silently promoted to floating point numbers, after which they will
711 start losing precision (their lower digits).
713 =head2 Large file support
715 If you have filesystems that support "large files" (files larger than
716 2 gigabytes), you may now also be able to create and access them from
717 Perl. You have to use Configure -Duselargefiles. Turning on the
718 large file support turns on also the 64-bit support on many platforms.
719 Beware that unless your filesystem also supports "sparse files" seeking
720 to umpteen petabytes may be unadvisable.
722 Note that in addition to requiring a proper file system to do large
723 files you may also need to adjust your per-process (or your
724 per-system, or per-process-group, or per-user-group) maximum filesize
725 limits before running Perl scripts that try to handle large files,
726 especially if you intend to write such files.
728 Finally, in addition to your process/process group maximum filesize
729 limits, you may have quota limits on your filesystems that stop you
730 (your user id or your user group id) from using large files.
732 Adjusting your process/user/group/file system/operating system limits
733 is outside the scope of Perl core language. For process limits, you
734 may try increasing the limits using your shell's limits/limit/ulimit
735 command before running Perl. The BSD::Resource extension (not
736 included with the standard Perl distribution) may also be of use, it
737 offers the getrlimit/setrlimit interface that can be used to adjust
738 process resource usage limits, including the maximum filesize limit.
742 In some systems you may be able to use long doubles to enhance the
743 range and precision of your double precision floating point numbers
744 (that is, Perl's numbers). Use Configure -Duselongdouble to enable
745 this support (if it is available).
749 You can "Configure -Dusemorebits" to turn on both the 64-bit support
750 and the long double support.
752 =head2 Enhanced support for sort() subroutines
754 Perl subroutines with a prototype of C<($$)> and XSUBs in general can
755 now be used as sort subroutines. In either case, the two elements to
756 be compared are passed as normal parameters in @_. See L<perlfunc/sort>.
758 For unprototyped sort subroutines, the historical behavior of passing
759 the elements to be compared as the global variables $a and $b remains
762 =head2 Better syntax checks on parenthesized unary operators
766 print defined(&foo,&bar,&baz);
767 print uc("foo","bar","baz");
770 used to be accidentally allowed in earlier versions, and produced
771 unpredictable behaviour. Some produced ancillary warnings
772 when used in this way; others silently did the wrong thing.
774 The parenthesized forms of most unary operators that expect a single
775 argument now ensure that they are not called with more than one
776 argument, making the cases shown above syntax errors. The usual
779 print defined &foo, &bar, &baz;
780 print uc "foo", "bar", "baz";
783 remains unchanged. See L<perlop>.
785 =head2 POSIX character class syntax [: :] supported
787 For example to match alphabetic characters use /[[:alpha:]]/.
788 See L<perlre> for details.
790 =head2 Improved C<qw//> operator
792 The C<qw//> operator is now evaluated at compile time into a true list
793 instead of being replaced with a run time call to C<split()>. This
794 removes the confusing misbehaviour of C<qw//> in scalar context, which
795 had inherited that behaviour from split().
799 $foo = ($bar) = qw(a b c); print "$foo|$bar\n";
801 now correctly prints "3|a", instead of "2|a".
803 =head2 pack() format 'Z' supported
805 The new format type 'Z' is useful for packing and unpacking null-terminated
806 strings. See L<perlfunc/"pack">.
808 =head2 pack() format modifier '!' supported
810 The new format type modifier '!' is useful for packing and unpacking
811 native shorts, ints, and longs. See L<perlfunc/"pack">.
813 =head2 pack() and unpack() support counted strings
815 The template character '/' can be used to specify a counted string
816 type to be packed or unpacked. See L<perlfunc/"pack">.
818 =head2 Comments in pack() templates
820 The '#' character in a template introduces a comment up to
821 end of the line. This facilitates documentation of pack()
824 =head2 $^X variables may now have names longer than one character
826 Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax
827 error. Now variable names that begin with a control character may be
828 arbitrarily long. However, for compatibility reasons, these variables
829 I<must> be written with explicit braces, as C<${^XY}> for example.
830 C<${^XYZ}> is synonymous with ${"\cXYZ"}. Variable names with more
831 than one control character, such as C<${^XY^Z}>, are illegal.
833 The old syntax has not changed. As before, `^X' may be either a
834 literal control-X character or the two-character sequence `caret' plus
835 `X'. When braces are omitted, the variable name stops after the
836 control character. Thus C<"$^XYZ"> continues to be synonymous with
837 C<$^X . "YZ"> as before.
839 As before, lexical variables may not have names beginning with control
840 characters. As before, variables whose names begin with a control
841 character are always forced to be in package `main'. All such variables
842 are reserved for future extensions, except those that begin with
843 C<^_>, which may be used by user programs and are guaranteed not to
844 acquire special meaning in any future version of Perl.
846 =head2 C<use attrs> implicit in subroutine attributes
848 Formerly, if you wanted to mark a subroutine as being a method call or
849 as requiring an automatic lock() when it is entered, you had to declare
850 that with a C<use attrs> pragma in the body of the subroutine.
851 That can now be accomplished with declaration syntax, like this:
853 sub mymethod : locked method ;
855 sub mymethod : locked method {
859 sub othermethod :locked :method ;
861 sub othermethod :locked :method {
866 (Note how only the first C<:> is mandatory, and whitespace surrounding
867 the C<:> is optional.)
869 F<AutoSplit.pm> and F<SelfLoader.pm> have been updated to keep the attributes
870 with the stubs they provide. See L<attributes>.
872 =head2 Regular expression improvements
874 change#2827,2373,2372,2365,1813,1800,4112,4158,4215,4301
875 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
877 =head2 Overloading improvements
880 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
882 =head2 open() with more than two arguments
884 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
886 =head2 Support for interpolating named characters
889 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
891 =head2 Experimental support for user-hooks in @INC
893 [TODO - Ken Fox <kfox@ford.com>]
895 =head2 C<require> and C<do> may be overridden
897 C<require> and C<do 'file'> operations may be overridden locally
898 by importing subroutines of the same name into the current package
899 (or globally by importing them into the CORE::GLOBAL:: namespace).
900 Overriding C<require> will also affect C<use>, provided the override
901 is visible at compile-time.
902 See L<perlsub/"Overriding Built-in Functions">.
904 =head2 New variable $^C reflects C<-c> switch
906 C<$^C> has a boolean value that reflects whether perl is being run
907 in compile-only mode (i.e. via the C<-c> switch). Since
908 BEGIN blocks are executed under such conditions, this variable
909 enables perl code to determine whether actions that make sense
910 only during normal running are warranted. See L<perlvar>.
912 =head2 New variable $^V contains Perl version in v5.6.0 format
914 C<$^V> contains the Perl version number as a string composed of
915 characters whose ordinals match the version numbers, so that it may
916 be used in string comparisons.
918 See C<Support for strings represented as a vector of ordinals> for an
921 =head2 Optional Y2K warnings
923 If Perl is built with the cpp macro C<PERL_Y2KWARN> defined,
924 it emits optional warnings when concatenating the number 19
927 This behavior must be specifically enabled when running Configure.
928 See F<INSTALL> and F<README.Y2K>.
930 =head1 Significant bug fixes
932 =head2 E<lt>HANDLEE<gt> on empty files
934 With C<$/> set to C<undef>, "slurping" an empty file returns a string of
935 zero length (instead of C<undef>, as it used to) the first time the
936 HANDLE is read after C<$/> is set to C<undef>. Further reads yield
939 This means that the following will append "foo" to an empty file (it used
942 perl -0777 -pi -e 's/^/foo/' empty_file
946 perl -pi -e 's/^/foo/' empty_file
948 is unchanged (it continues to leave the file empty).
950 =head2 C<eval '...'> improvements
952 Line numbers (as reflected by caller() and most diagnostics) within
953 C<eval '...'> were often incorrect when here documents were involved.
954 This has been corrected.
956 Lexical lookups for variables appearing in C<eval '...'> within
957 functions that were themselves called within an C<eval '...'> were
958 searching the wrong place for lexicals. The lexical search now
959 correctly ends at the subroutine's block boundary.
961 Parsing of here documents used to be flawed when they appeared as
962 the replacement expression in C<eval 's/.../.../e'>. This has
965 =head2 All compilation errors are true errors
967 Some "errors" encountered at compile time were by neccessity
968 generated as warnings followed by eventual termination of the
969 program. This enabled more such errors to be reported in a
970 single run, rather than causing a hard stop at the first error
971 that was encountered.
973 The mechanism for reporting such errors has been reimplemented
974 to queue compile-time errors and report them at the end of the
975 compilation as true errors rather than as warnings. This fixes
976 cases where error messages leaked through in the form of warnings
977 when code was compiled at run time using C<eval STRING>, and
978 also allows such errors to be reliably trapped using __DIE__ hooks.
980 =head2 Automatic flushing of output buffers
982 fork(), exec(), system(), qx//, and pipe open()s now flush buffers
983 of all files opened for output when the operation
984 was attempted. This mostly eliminates confusing
985 buffering mishaps suffered by users unaware of how Perl internally
988 =head2 Better diagnostics on meaningless filehandle operations
990 Constructs such as C<open(E<lt>FHE<gt>)> and C<close(E<lt>FHE<gt>)>
991 are compile time errors. Attempting to read from filehandles that
992 were opened only for writing will now produce warnings (just as
993 writing to read-only filehandles does).
995 =head2 Where possible, buffered data discarded from duped input filehandle
997 C<open(NEW, "E<lt>&OLD")> now attempts to discard any data that
998 was previously read and buffered in C<OLD> before duping the handle.
999 On platforms where doing this is allowed, the next read operation
1000 on C<NEW> will return the same data as the corresponding operation
1001 on C<OLD>. Formerly, it would have returned the data from the start
1002 of the following disk block instead.
1004 =head2 eof() has the same old magic as <>
1006 C<eof()> would return true if no attempt to read from C<E<lt>E<gt>> had
1007 yet been made. C<eof()> has been changed to have a little magic of its
1008 own, it now opens the C<E<lt>E<gt>> files.
1010 =head2 system(), backticks and pipe open now reflect exec() failure
1012 On Unix and similar platforms, system(), qx() and open(FOO, "cmd |")
1013 etc., are implemented via fork() and exec(). When the underlying
1014 exec() fails, earlier versions did not report the error properly,
1015 since the exec() happened to be in a different process.
1017 The child process now communicates with the parent about the
1018 error in launching the external command, which allows these
1019 constructs to return with their usual error value and set $!.
1021 =head2 Implicitly closed filehandles are safer
1023 Sometimes implicitly closed filehandles (as when they are localized,
1024 and Perl automatically closes them on exiting the scope) could
1025 inadvertently set $? or $!. This has been corrected.
1027 =head2 C<(\$)> prototype and C<$foo{a}>
1029 An scalar reference prototype now correctly allows a hash or
1030 array element in that slot.
1032 =head2 Pseudo-hashes work better
1034 Dereferencing some types of reference values in a pseudo-hash,
1035 such as C<$ph-E<gt>{foo}[1]>, was accidentally disallowed. This has
1038 When applied to a pseudo-hash element, exists() now reports whether
1039 the specified value exists, not merely if the key is valid.
1041 delete() now works on pseudo-hashes. When given a pseudo-hash element
1042 or slice it deletes the values corresponding to the keys (but not the keys
1043 themselves). See L<perlref/"Pseudo-hashes: Using an array as a hash">.
1045 =head2 C<goto &sub> and AUTOLOAD
1047 The C<goto &sub> construct works correctly when C<&sub> happens
1050 =head2 C<-bareword> allowed under C<use integer>
1052 The autoquoting of barewords preceded by C<-> did not work
1053 in prior versions when the C<integer> pragma was enabled.
1054 This has been fixed.
1056 =head2 Boolean assignment operators are legal lvalues
1058 Constructs such as C<($a ||= 2) += 1> are now allowed.
1060 =head2 C<sort $coderef @foo> allowed
1062 sort() did not accept a subroutine reference as the comparison
1063 function in earlier versions. This is now permitted.
1065 =head2 Failures in DESTROY()
1067 When code in a destructor threw an exception, it went unnoticed
1068 in earlier versions of Perl, unless someone happened to be
1069 looking in $@ just after the point the destructor happened to
1070 run. Such failures are now visible as warnings when warnings are
1073 =head2 Locale bugs fixed
1075 printf() and sprintf() previously reset the numeric locale
1076 back to the default "C" locale. This has been fixed.
1078 Numbers formatted according to the local numeric locale
1079 (such as using a decimal comma instead of a decimal dot) caused
1080 "isn't numeric" warnings, even while the operations accessing
1081 those numbers produced correct results. The warnings are gone.
1085 The C<eval 'return sub {...}'> construct could sometimes leak
1086 memory. This has been fixed.
1088 Operations that aren't filehandle constructors used to leak memory
1089 when used on invalid filehandles. This has been fixed.
1091 Constructs that modified C<@_> could fail to deallocate values
1092 in C<@_> and thus leak memory. This has been corrected.
1094 =head2 Spurious subroutine stubs after failed subroutine calls
1096 Perl could sometimes create empty subroutine stubs when a
1097 subroutine was not found in the package. Such cases stopped
1098 later method lookups from progressing into base packages.
1099 This has been corrected.
1101 =head2 Consistent numeric conversions
1104 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1106 =head2 Taint failures under C<-U>
1108 When running in unsafe mode, taint violations could sometimes
1109 cause silent failures. This has been fixed.
1111 =head2 END blocks and the C<-c> switch
1113 Prior versions used to run BEGIN B<and> END blocks when Perl was
1114 run in compile-only mode. Since this is typically not the expected
1115 behavior, END blocks are not executed anymore when the C<-c> switch
1118 See L<CHECK blocks> for how to run things when the compile phase ends.
1120 =head2 Potential to leak DATA filehandles
1122 Using the C<__DATA__> token creates an implicit filehandle to
1123 the file that contains the token. It is the program's
1124 responsibility to close it when it is done reading from it.
1126 This caveat is now better explained in the documentation.
1129 =head2 Diagnostics follow STDERR
1131 Diagnostic output now goes to whichever file the C<STDERR> handle
1132 is pointing at, instead of always going to the underlying C runtime
1133 library's C<stderr>.
1135 =head2 Other fixes for better diagnostics
1137 Line numbers are no longer suppressed (under most likely circumstances)
1138 during the global destruction phase.
1140 Diagnostics emitted from code running in threads other than the main
1141 thread are now accompanied by the thread ID.
1143 Embedded null characters in diagnostics now actually show up. They
1144 used to truncate the message in prior versions.
1146 $foo::a and $foo::b are now exempt from "possible typo" warnings only
1147 if sort() is encountered in package foo.
1149 Unrecognized alphabetic escapes encountered when parsing quote
1150 constructs now generate a warning, since they may take on new
1151 semantics in later versions of Perl.
1153 =head1 Performance enhancements
1155 =head2 Simple sort() using { $a <=> $b } and the like are optimized
1157 Many common sort() operations using a simple inlined block are now
1158 optimized for faster performance.
1160 =head2 Optimized assignments to lexical variables
1162 Certain operations in the RHS of assignment statements have been
1163 optimized to directly set the lexical variable on the LHS,
1164 eliminating redundant copying overheads.
1166 =head2 Method lookups optimized
1168 [TODO - Chip Salzenberg <chip@perlsupport.com>]
1170 =head2 Faster mechanism to invoke XSUBs
1173 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1175 =head2 Perl_malloc() improvements
1178 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1180 =head2 Faster subroutine calls
1182 Minor changes in how subroutine calls are handled internally
1183 provide marginal improvements in performance.
1185 =head1 Platform specific changes
1187 =head2 Additional supported platforms
1193 VM/ESA is now supported.
1197 Siemens BS2000 is now supported under the POSIX Shell.
1201 The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread
1206 GNU/Hurd is now supported.
1210 Rhapsody is now supported.
1214 EPOC is is now supported (on Psion 5).
1224 Perl now works with djgpp 2.02 (and 2.03 alpha).
1228 Environment variable names are not converted to uppercase any more.
1232 Wrong exit code from backticks now fixed.
1236 This port is still using its own builtin globbing.
1242 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1246 [TODO - Charles Bailey <bailey@newman.upenn.edu>]
1250 Site library searches failed to look for ".../site/5.XXX/lib"
1251 if ".../site/5.XXXYY/lib" wasn't found. This has been corrected.
1253 When given a pathname that consists only of a drivename, such
1254 as C<A:>, opendir() and stat() now use the current working
1255 directory for the drive rather than the drive root.
1257 The builtin XSUB functions in the Win32:: namespace are
1258 documented. See L<Win32>.
1260 $^X now contains the full path name of the running executable.
1262 A Win32::GetLongPathName() function is provided to complement
1263 Win32::GetFullPathName() and Win32::GetShortPathName(). See L<Win32>.
1265 POSIX::uname() is supported.
1267 system(1,...) now returns true process IDs rather than process
1268 handles. kill() accepts any real process id, rather than strictly
1269 return values from system(1,...).
1271 The C<Shell> module is supported.
1273 Rudimentary support for building under command.com in Windows 95
1276 Scripts are read in binary mode by default to allow ByteLoader (and
1277 the filter mechanism in general) to work properly. For compatibility,
1278 the DATA filehandle will be set to text mode if a carriage return is
1279 detected at the end of the line containing the __END__ or __DATA__
1280 token; if not, the DATA filehandle will be left open in binary mode.
1281 Earlier versions always opened the DATA filehandle in text mode.
1283 The glob() operator is implemented via the L<File::Glob> extension,
1284 which supports glob syntax of the C shell. This increases the flexibility
1285 of the glob() operator, but there may be compatibility issues for
1286 programs that relied on the older globbing syntax. If you want to
1287 preserve compatibility with the older syntax, you might want to put
1288 a C<use File::DosGlob;> in your program. For details and compatibility
1289 information, see L<File::Glob>.
1299 Compatibility tests for C<sub : attrs> vs the older C<use attrs>.
1303 IO constants (SEEK_*, _IO*).
1307 Directory-related IO methods (new, read, close, rewind, tied delete).
1309 =item lib/io_multihomed
1311 INET sockets with multi-homed hosts.
1323 Regression tests for C<my ($x,@y,%z) : attrs> and <sub : attrs>.
1327 File test operators.
1331 Verify operations that access pad objects (lexicals and temporaries).
1335 Verify C<exists &sub> operations.
1339 =head1 Modules and Pragmata
1347 While used internally by Perl as a pragma, this module also
1348 provides a way to fetch subroutine and variable attributes.
1353 The Perl Compiler suite has been extensively reworked for this
1356 [TODO - Vishal Bhatia <vishal@gol.com>,
1357 Nick Ing-Simmons <nick@ni-s.u-net.com>]
1361 The ByteLoader is a dedicated extension to generate and run
1362 Perl bytecode. See L<ByteLoader>.
1366 References can now be used.
1368 The new version also allows a leading underscore in constant names, but
1369 disallows a double leading underscore (as in "__LINE__"). Some other names
1370 are disallowed or warned against, including BEGIN, END, etc. Some names
1371 which were forced into main:: used to fail silently in some cases; now they're
1372 fatal (outside of main::) and an optional warning (inside of main::).
1373 The ability to detect whether a constant had been set with a given name has
1381 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1385 A C<Maxdepth> setting can be specified to avoid venturing
1386 too deeply into deep data structures. See L<Data::Dumper>.
1388 Dumping C<qr//> objects works correctly.
1392 C<DB> is an experimental module that exposes a clean abstraction
1393 to Perl's debugging API.
1397 DB_File can now be built with Berkeley DB versions 1, 2 or 3.
1398 See C<ext/DB_File/Changes>.
1402 Devel::DProf, a Perl source code profiler has been added. See
1403 L<Devel::DProf> and L<dprofpp>.
1407 The Dumpvalue module provides screen dumps of Perl data.
1411 Overall, Benchmark results exhibit lower average error and better timing
1414 You can now run tests for I<n> seconds instead of guessing the right
1415 number of tests to run: e.g. timethese(-5, ...) will run each
1416 code for at least 5 CPU seconds. Zero as the "number of repetitions"
1417 means "for at least 3 CPU seconds". The output format has also
1418 changed. For example:
1420 use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
1422 will now output something like this:
1424 Benchmark: running a, b, each for at least 5 CPU seconds...
1425 a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
1426 b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
1428 New features: "each for at least N CPU seconds...", "wallclock secs",
1429 and the "@ operations/CPU second (n=operations)".
1431 timethese() now returns a reference to a hash of Benchmark objects containing
1432 the test results, keyed on the names of the tests.
1434 timethis() now returns the iterations field in the Benchmark result object
1437 timethese(), timethis(), and the new cmpthese() (see below) can also take
1438 a format specifier of 'none' to suppress output.
1440 A new function countit() is just like timeit() except that it takes a
1441 TIME instead of a COUNT.
1443 A new function cmpthese() prints a chart comparing the results of each test
1444 returned from a timethese() call. For each possible pair of tests, the
1445 percentage speed difference (iters/sec or seconds/iter) is shown.
1447 For other details, see L<Benchmark>.
1451 The Devel::Peek module provides access to the internal representation
1452 of Perl variables and data. It is a data debugging tool for the XS programmer.
1456 $PERL_VERSION now stands for C<$^V> (a string value) rather than for C<$]>
1459 =item ExtUtils::MakeMaker
1461 change#4135, also needs docs in module pod
1462 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1466 More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for
1467 large file (more than 4GB) access Note that the O_LARGEFILE is
1468 automatically/transparently added to sysopen() flags if large file
1469 support has been configured), Free/Net/OpenBSD locking behaviour flags
1470 F_FLOCK, F_POSIX, Linux F_SHLCK, and O_ACCMODE: the combined mask of
1471 O_RDONLY, O_WRONLY, and O_RDWR. The seek()/sysseek() constants
1472 SEEK_SET, SEEK_CUR, and SEEK_END are available via the C<:seek> tag.
1473 The chmod()/stat() S_IF* constants and S_IS* functions are available
1474 via the C<:mode> tag.
1479 A compare_text() function has been added, which allows custom
1480 comparison functions. See L<File::Compare>.
1484 File::Find now works correctly when the wanted() function is either
1485 autoloaded or is a symbolic reference.
1487 A bug that caused File::Find to lose track of the working directory
1488 when pruning top-level directories has been fixed.
1490 File::Find now also supports several other options to control its
1491 behavior. It can follow symbolic links if the C<follow> option is
1492 specified. Enabling the C<no_chdir> option will make File::Find skip
1493 changing the current directory when walking directories. The C<untaint>
1494 flag can be useful when running with taint checks enabled.
1500 This extension implements BSD-style file globbing. By default,
1501 it will also be used for the internal implementation of the glob()
1502 operator. See L<File::Glob>.
1506 New methods have been added to the File::Spec module: devnull() returns
1507 the name of the null device (/dev/null on Unix) and tmpdir() the name of
1508 the temp directory (normally /tmp on Unix). There are now also methods
1509 to convert between absolute and relative filenames: abs2rel() and
1510 rel2abs(). For compatibility with operating systems that specify volume
1511 names in file paths, the splitpath(), splitdir(), and catdir() methods
1514 =item File::Spec::Functions
1516 The new File::Spec::Functions modules provides a function interface
1517 to the File::Spec module. Allows shorthand
1519 $fullname = catfile($dir1, $dir2, $file);
1523 $fullname = File::Spec->catfile($dir1, $dir2, $file);
1527 Getopt::Long licensing has changed to allow the Perl Artistic License
1528 as well as the GPL. It used to be GPL only, which got in the way of
1529 non-GPL applications that wanted to use Getopt::Long.
1531 Getopt::Long encourages the use of Pod::Usage to produce help
1532 messages. For example:
1538 GetOptions('help|?' => \$help, man => \$man) or pod2usage(2);
1539 pod2usage(1) if $help;
1540 pod2usage(-exitstatus => 0, -verbose => 2) if $man;
1546 sample - Using GetOpt::Long and Pod::Usage
1550 sample [options] [file ...]
1553 -help brief help message
1554 -man full documentation
1562 Print a brief help message and exits.
1566 Prints the manual page and exits.
1572 B<This program> will read the given input file(s) and do someting
1573 useful with the contents thereof.
1577 See L<Pod::Usage> for details.
1579 A bug that prevented the non-option call-back E<lt>E<gt> from being
1580 specified as the first argument has been fixed.
1582 To specify the characters E<lt> and E<gt> as option starters, use
1583 E<gt>E<lt>. Note, however, that changing option starters is strongly
1588 write() and syswrite() will now accept a single-argument
1589 form of the call, for consistency with Perl's syswrite().
1591 You can now create a TCP-based IO::Socket::INET without forcing
1592 a connect attempt. This allows you to configure its options
1593 (like making it non-blocking) and then call connect() manually.
1595 A bug that prevented the IO::Socket::protocol() accessor
1596 from ever returning the correct value has been corrected.
1600 Java Perl Lingo is now distributed with Perl. See jpl/README
1601 for more information.
1605 C<use lib> now weeds out any trailing duplicate entries.
1606 C<no lib> removes all named entries.
1610 The bitwise operations C<E<lt>E<lt>>, C<E<gt>E<gt>>, C<&>, C<|>,
1611 and C<~> are now supported on bigints.
1615 The accessor methods Re, Im, arg, abs, rho, and theta can now also
1616 act as mutators (accessor $z->Re(), mutator $z->Re(3)).
1620 A little bit of radial trigonometry (cylindrical and spherical),
1621 radial coordinate conversions, and the great circle distance were added.
1623 =item Pod::Parser, Pod::InputObjects
1625 Pod::Parser is a base class for parsing and selecting sections of
1626 pod documentation from an input stream. This module takes care of
1627 identifying pod paragraphs and commands in the input and hands off the
1628 parsed paragraphs and commands to user-defined methods which are free
1629 to interpret or translate them as they see fit.
1631 Pod::InputObjects defines some input objects needed by Pod::Parser, and
1632 for advanced users of Pod::Parser that need more about a command besides
1635 As of release 5.6 of Perl, Pod::Parser is now the officially sanctioned
1636 "base parser code" recommended for use by all pod2xxx translators.
1637 Pod::Text (pod2text) and Pod::Man (pod2man) have already been converted
1638 to use Pod::Parser and efforts to convert Pod::HTML (pod2html) are already
1639 underway. For any questions or comments about pod parsing and translating
1640 issues and utilities, please use the pod-people@perl.org mailing list.
1642 For further information, please see L<Pod::Parser> and L<Pod::InputObjects>.
1644 =item Pod::Checker, podchecker
1646 This utility checks pod files for correct syntax, according to
1647 L<perlpod>. Obvious errors are flagged as such, while warnings are
1648 printed for mistakes that can be handled gracefully. The checklist is
1649 not complete yet. See L<Pod::Checker>.
1651 =item Pod::ParseUtils, Pod::Find
1653 These modules provide a set of gizmos that are useful mainly for pod
1654 translators. L<Pod::Find|Pod::Find> traverses directory structures and
1655 returns found pod files, along with their canonical names (like
1656 C<File::Spec::Unix>). L<Pod::ParseUtils|Pod::ParseUtils> contains
1657 B<Pod::List> (useful for storing pod list information), B<Pod::Hyperlink>
1658 (for parsing the contents of C<LE<gt>E<lt>> sequences) and B<Pod::Cache>
1659 (for caching information about pod files, e.g. link nodes).
1661 =item Pod::Select, podselect
1663 Pod::Select is a subclass of Pod::Parser which provides a function
1664 named "podselect()" to filter out user-specified sections of raw pod
1665 documentation from an input stream. podselect is a script that provides
1666 access to Pod::Select from other scripts to be used as a filter.
1669 =item Pod::Usage, pod2usage
1671 Pod::Usage provides the function "pod2usage()" to print usage messages for
1672 a Perl script based on its embedded pod documentation. The pod2usage()
1673 function is generally useful to all script authors since it lets them
1674 write and maintain a single source (the pods) for documentation, thus
1675 removing the need to create and maintain redundant usage message text
1676 consisting of information already in the pods.
1678 There is also a pod2usage script which can be used from other kinds of
1679 scripts to print usage messages from pods (even for non-Perl scripts
1680 with pods embedded in comments).
1682 For details and examples, please see L<Pod::Usage>.
1684 =item Pod::Text and Pod::Man
1686 [TODO - Russ Allbery <rra@stanford.edu>]
1690 An EXISTS method has been added to this module (and sdbm_exists() has
1691 been added to the underlying sdbm library), so one can now call exists
1692 on an SDBM_File tied hash and get the correct result, rather than a
1695 A bug that may have caused data loss when more than one disk block
1696 happens to be read from the database in a single FETCH() has been
1701 Sys::Syslog now uses XSUBs to access facilities from syslog.h so it
1702 no longer requires syslog.ph to exist.
1706 Sys::Hostname now uses XSUBs to call the C library's gethostname() or
1707 uname() if they exist.
1711 The timelocal() and timegm() functions used to silently return bogus
1712 results when the date fell outside the machine's integer range. They
1713 now consistently croak() if the date falls in an unsupported range.
1717 The error return value in list context has been changed for all functions
1718 that return a list of values. Previously these functions returned a list
1719 with a single element C<undef> if an error occurred. Now these functions
1720 return the empty list in these situations. This applies to the following
1726 The remaining functions are unchanged and continue to return C<undef> on
1727 error even in list context.
1729 The Win32::SetLastError(ERROR) function has been added as a complement
1730 to the Win32::GetLastError() function.
1732 The new Win32::GetFullPathName(FILENAME) returns the full absolute
1733 pathname for FILENAME in scalar context. In list context it returns
1734 a two-element list containing the fully qualified directory name and
1735 the filename. See L<Win32>.
1739 A new feature called "DBM Filters" has been added to all the
1740 DBM modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File.
1741 DBM Filters add four new methods to each DBM module:
1748 These can be used to filter key-value pairs before the pairs are
1749 written to the database or just after they are read from the database.
1750 See L<perldbmfilter> for further information.
1756 C<use attrs> is now obsolete, and is only provided for
1757 backward-compatibility. It's been replaced by the C<sub : attributes>
1758 syntax. See L<perlsub/"Subroutine Attributes"> and L<attributes>.
1760 C<use utf8> to enable UTF-8 and Unicode support.
1762 Lexical warnings pragma, C<use warnings;>, to control optional warnings.
1765 C<use filetest> to control the behaviour of filetests (C<-r> C<-w>
1766 ...). Currently only one subpragma implemented, "use filetest
1767 'access';", that uses access(2) or equivalent to check permissions
1768 instead of using stat(2) as usual. This matters in filesystems
1769 where there are ACLs (access control lists): the stat(2) might lie,
1770 but access(2) knows better.
1772 =head1 Utility Changes
1776 [TODO - Kurt Starsinic <kstar@chapin.edu>]
1780 C<perlcc> now supports the C and Bytecode backends. By default,
1781 it generates output from the simple C backend rather than the
1782 optimized C backend.
1784 Support for non-Unix platforms has been improved.
1789 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1791 =head1 Documentation Changes
1797 The official list of public Perl API functions.
1799 =item perlcompile.pod
1801 An introduction to using the Perl Compiler suite.
1803 =item perlfilter.pod
1805 An introduction to writing Perl source filters.
1809 Some guidelines for hacking the Perl source code.
1811 =item perlintern.pod
1813 A list of internal functions in the Perl source code.
1814 (List is currently empty.)
1816 =item perlopentut.pod
1818 A tutorial on using open() effectively.
1820 =item perlreftut.pod
1822 A tutorial that introduces the essentials of references.
1826 A tutorial on managing class data for object modules.
1828 =item perlunicode.pod
1830 An introduction to Unicode support features in Perl.
1834 =head1 New or Changed Diagnostics
1838 =item "%s" variable %s masks earlier declaration in same %s
1840 (W) A "my" or "our" variable has been redeclared in the current scope or statement,
1841 effectively eliminating all access to the previous instance. This is almost
1842 always a typographical error. Note that the earlier variable will still exist
1843 until the end of the scope or until all closure referents to it are
1846 =item "my sub" not yet implemented
1848 (F) Lexically scoped subroutines are not yet implemented. Don't try that
1851 =item "our" variable %s redeclared
1853 (W) You seem to have already declared the same global once before in the
1854 current lexical scope.
1856 =item '!' allowed only after types %s
1858 (F) The '!' is allowed in pack() and unpack() only after certain types.
1859 See L<perlfunc/pack>.
1861 =item / cannot take a count
1863 (F) You had an unpack template indicating a counted-length string,
1864 but you have also specified an explicit size for the string.
1865 See L<perlfunc/pack>.
1867 =item / must be followed by a, A or Z
1869 (F) You had an unpack template indicating a counted-length string,
1870 which must be followed by one of the letters a, A or Z
1871 to indicate what sort of string is to be unpacked.
1872 See L<perlfunc/pack>.
1874 =item / must be followed by a*, A* or Z*
1876 (F) You had a pack template indicating a counted-length string,
1877 Currently the only things that can have their length counted are a*, A* or Z*.
1878 See L<perlfunc/pack>.
1880 =item / must follow a numeric type
1882 (F) You had an unpack template that contained a '#',
1883 but this did not follow some numeric unpack specification.
1884 See L<perlfunc/pack>.
1886 =item /%s/: Unrecognized escape \\%c passed through
1888 (W) You used a backslash-character combination which is not recognized
1889 by Perl. This combination appears in an interpolated variable or a
1890 C<'>-delimited regular expression. The character was understood literally.
1892 =item /%s/: Unrecognized escape \\%c in character class passed through
1894 (W) You used a backslash-character combination which is not recognized
1895 by Perl inside character classes. The character was understood literally.
1897 =item /%s/ should probably be written as "%s"
1899 (W) You have used a pattern where Perl expected to find a string,
1900 as in the first argument to C<join>. Perl will treat the true
1901 or false result of matching the pattern against $_ as the string,
1902 which is probably not what you had in mind.
1904 =item %s() called too early to check prototype
1906 (W) You've called a function that has a prototype before the parser saw a
1907 definition or declaration for it, and Perl could not check that the call
1908 conforms to the prototype. You need to either add an early prototype
1909 declaration for the subroutine in question, or move the subroutine
1910 definition ahead of the call to get proper prototype checking. Alternatively,
1911 if you are certain that you're calling the function correctly, you may put
1912 an ampersand before the name to avoid the warning. See L<perlsub>.
1914 =item %s argument is not a HASH or ARRAY element
1916 (F) The argument to exists() must be a hash or array element, such as:
1919 $ref->[12]->["susie"]
1921 =item %s argument is not a HASH or ARRAY element or slice
1923 (F) The argument to delete() must be either a hash or array element, such as:
1926 $ref->[12]->["susie"]
1928 or a hash or array slice, such as:
1930 @foo[$bar, $baz, $xyzzy]
1931 @{$ref->[12]}{"susie", "queue"}
1933 =item %s argument is not a subroutine name
1935 (F) The argument to exists() for C<exists &sub> must be a subroutine
1936 name, and not a subroutine call. C<exists &sub()> will generate this error.
1938 =item %s package attribute may clash with future reserved word: %s
1940 (W) A lowercase attribute name was used that had a package-specific handler.
1941 That name might have a meaning to Perl itself some day, even though it
1942 doesn't yet. Perhaps you should use a mixed-case attribute name, instead.
1945 =item (in cleanup) %s
1947 (W) This prefix usually indicates that a DESTROY() method raised
1948 the indicated exception. Since destructors are usually called by
1949 the system at arbitrary points during execution, and often a vast
1950 number of times, the warning is issued only once for any number
1951 of failures that would otherwise result in the same message being
1954 Failure of user callbacks dispatched using the C<G_KEEPERR> flag
1955 could also result in this warning. See L<perlcall/G_KEEPERR>.
1957 =item <> should be quotes
1959 (F) You wrote C<require E<lt>fileE<gt>> when you should have written
1962 =item Attempt to join self
1964 (F) You tried to join a thread from within itself, which is an
1965 impossible task. You may be joining the wrong thread, or you may
1966 need to move the join() to some other thread.
1968 =item Bad evalled substitution pattern
1970 (F) You've used the /e switch to evaluate the replacement for a
1971 substitution, but perl found a syntax error in the code to evaluate,
1972 most likely an unexpected right brace '}'.
1974 =item Bad realloc() ignored
1976 (S) An internal routine called realloc() on something that had never been
1977 malloc()ed in the first place. Mandatory, but can be disabled by
1978 setting environment variable C<PERL_BADFREE> to 1.
1980 =item Bareword found in conditional
1982 (W) The compiler found a bareword where it expected a conditional,
1983 which often indicates that an || or && was parsed as part of the
1984 last argument of the previous construct, for example:
1988 It may also indicate a misspelled constant that has been interpreted
1991 use constant TYPO => 1;
1992 if (TYOP) { print "foo" }
1994 The C<strict> pragma is useful in avoiding such errors.
1996 =item Binary number > 0b11111111111111111111111111111111 non-portable
1998 (W) The binary number you specified is larger than 2**32-1
1999 (4294967295) and therefore non-portable between systems. See
2000 L<perlport> for more on portability concerns.
2002 =item Bit vector size > 32 non-portable
2004 (W) Using bit vector sizes larger than 32 is non-portable.
2006 =item Buffer overflow in prime_env_iter: %s
2008 (W) A warning peculiar to VMS. While Perl was preparing to iterate over
2009 %ENV, it encountered a logical name or symbol definition which was too long,
2010 so it was truncated to the string shown.
2012 =item Can't check filesystem of script "%s"
2014 (P) For some reason you can't check the filesystem of the script for nosuid.
2016 =item Can't declare class for non-scalar %s in "%s"
2018 (S) Currently, only scalar variables can declared with a specific class
2019 qualifier in a "my" or "our" declaration. The semantics may be extended
2020 for other types of variables in future.
2022 =item Can't declare %s in "%s"
2024 (F) Only scalar, array, and hash variables may be declared as "my" or
2025 "our" variables. They must have ordinary identifiers as names.
2027 =item Can't ignore signal CHLD, forcing to default
2029 (W) Perl has detected that it is being run with the SIGCHLD signal
2030 (sometimes known as SIGCLD) disabled. Since disabling this signal
2031 will interfere with proper determination of exit status of child
2032 processes, Perl has reset the signal to its default value.
2033 This situation typically indicates that the parent program under
2034 which Perl may be running (e.g. cron) is being very careless.
2036 =item Can't modify non-lvalue subroutine call
2038 (F) Subroutines meant to be used in lvalue context should be declared as
2039 such, see L<perlsub/"Lvalue subroutines">.
2041 =item Can't read CRTL environ
2043 (S) A warning peculiar to VMS. Perl tried to read an element of %ENV
2044 from the CRTL's internal environment array and discovered the array was
2045 missing. You need to figure out where your CRTL misplaced its environ
2046 or define F<PERL_ENV_TABLES> (see L<perlvms>) so that environ is not searched.
2048 =item Can't remove %s: %s, skipping file
2050 (S) You requested an inplace edit without creating a backup file. Perl
2051 was unable to remove the original file to replace it with the modified
2052 file. The file was left unmodified.
2054 =item Can't return %s from lvalue subroutine
2056 (F) Perl detected an attempt to return illegal lvalues (such
2057 as temporary or readonly values) from a subroutine used as an lvalue.
2058 This is not allowed.
2060 =item Can't weaken a nonreference
2062 (F) You attempted to weaken something that was not a reference. Only
2063 references can be weakened.
2065 =item Character class [:%s:] unknown
2067 (F) The class in the character class [: :] syntax is unknown.
2070 =item Character class syntax [%s] belongs inside character classes
2072 (W) The character class constructs [: :], [= =], and [. .] go
2073 I<inside> character classes, the [] are part of the construct,
2074 for example: /[012[:alpha:]345]/. Note that [= =] and [. .]
2075 are not currently implemented; they are simply placeholders for
2078 =item Constant is not %s reference
2080 (F) A constant value (perhaps declared using the C<use constant> pragma)
2081 is being dereferenced, but it amounts to the wrong type of reference. The
2082 message indicates the type of reference that was expected. This usually
2083 indicates a syntax error in dereferencing the constant value.
2084 See L<perlsub/"Constant Functions"> and L<constant>.
2086 =item constant(%s): %%^H is not localized
2088 (F) When setting compile-time-lexicalized hash %^H one should set the
2089 corresponding bit of $^H as well.
2091 =item constant(%s): %s
2093 (F) Compile-time-substitutions (such as overloaded constants and
2094 character names) were not correctly set up.
2096 =item defined(@array) is deprecated
2098 (D) defined() is not usually useful on arrays because it checks for an
2099 undefined I<scalar> value. If you want to see if the array is empty,
2100 just use C<if (@array) { # not empty }> for example.
2102 =item defined(%hash) is deprecated
2104 (D) defined() is not usually useful on hashes because it checks for an
2105 undefined I<scalar> value. If you want to see if the hash is empty,
2106 just use C<if (%hash) { # not empty }> for example.
2108 =item Did not produce a valid header
2112 =item Did you mean "local" instead of "our"?
2114 (W) Remember that "our" does not localize the declared global variable.
2115 You have declared it again in the same lexical scope, which seems superfluous.
2117 =item Document contains no data
2121 =item entering effective %s failed
2123 (F) While under the C<use filetest> pragma, switching the real and
2124 effective uids or gids failed.
2126 =item false [] range "%s" in regexp
2128 (W) A character class range must start and end at a literal character, not
2129 another character class like C<\d> or C<[:alpha:]>. The "-" in your false
2130 range is interpreted as a literal "-". Consider quoting the "-", "\-".
2133 =item Filehandle %s opened only for output
2135 (W) You tried to read from a filehandle opened only for writing. If you
2136 intended it to be a read/write filehandle, you needed to open it with
2137 "+E<lt>" or "+E<gt>" or "+E<gt>E<gt>" instead of with "E<lt>" or nothing. If
2138 you intended only to read from the file, use "E<lt>". See
2141 =item flock() on closed filehandle %s
2143 (W) The filehandle you're attempting to flock() got itself closed some
2144 time before now. Check your logic flow. flock() operates on filehandles.
2145 Are you attempting to call flock() on a dirhandle by the same name?
2147 =item Global symbol "%s" requires explicit package name
2149 (F) You've said "use strict vars", which indicates that all variables
2150 must either be lexically scoped (using "my"), declared beforehand using
2151 "our", or explicitly qualified to say which package the global variable
2154 =item Hexadecimal number > 0xffffffff non-portable
2156 (W) The hexadecimal number you specified is larger than 2**32-1
2157 (4294967295) and therefore non-portable between systems. See
2158 L<perlport> for more on portability concerns.
2160 =item Ill-formed CRTL environ value "%s"
2162 (W) A warning peculiar to VMS. Perl tried to read the CRTL's internal
2163 environ array, and encountered an element without the C<=> delimiter
2164 used to spearate keys from values. The element is ignored.
2166 =item Ill-formed message in prime_env_iter: |%s|
2168 (W) A warning peculiar to VMS. Perl tried to read a logical name
2169 or CLI symbol definition when preparing to iterate over %ENV, and
2170 didn't see the expected delimiter between key and value, so the
2173 =item Illegal binary digit %s
2175 (F) You used a digit other than 0 or 1 in a binary number.
2177 =item Illegal binary digit %s ignored
2179 (W) You may have tried to use a digit other than 0 or 1 in a binary number.
2180 Interpretation of the binary number stopped before the offending digit.
2182 =item Illegal number of bits in vec
2184 (F) The number of bits in vec() (the third argument) must be a power of
2185 two from 1 to 32 (or 64, if your platform supports that).
2187 =item Integer overflow in %s number
2189 (W) The hexadecimal, octal or binary number you have specified either
2190 as a literal or as an argument to hex() or oct() is too big for your
2191 architecture, and has been converted to a floating point number. On a
2192 32-bit architecture the largest hexadecimal, octal or binary number
2193 representable without overflow is 0xFFFFFFFF, 037777777777, or
2194 0b11111111111111111111111111111111 respectively. Note that Perl
2195 transparently promotes all numbers to a floating point representation
2196 internally--subject to loss of precision errors in subsequent
2199 =item Invalid %s attribute: %s
2201 The indicated attribute for a subroutine or variable was not recognized
2202 by Perl or by a user-supplied handler. See L<attributes>.
2204 =item Invalid %s attributes: %s
2206 The indicated attributes for a subroutine or variable were not recognized
2207 by Perl or by a user-supplied handler. See L<attributes>.
2209 =item invalid [] range "%s" in regexp
2211 The offending range is now explicitly displayed.
2213 =item Invalid separator character %s in attribute list
2215 (F) Something other than a colon or whitespace was seen between the
2216 elements of an attribute list. If the previous attribute
2217 had a parenthesised parameter list, perhaps that list was terminated
2218 too soon. See L<attributes>.
2220 =item Invalid separator character %s in subroutine attribute list
2222 (F) Something other than a colon or whitespace was seen between the
2223 elements of a subroutine attribute list. If the previous attribute
2224 had a parenthesised parameter list, perhaps that list was terminated
2227 =item leaving effective %s failed
2229 (F) While under the C<use filetest> pragma, switching the real and
2230 effective uids or gids failed.
2232 =item Lvalue subs returning %s not implemented yet
2234 (F) Due to limitations in the current implementation, array and hash
2235 values cannot be returned in subroutines used in lvalue context.
2236 See L<perlsub/"Lvalue subroutines">.
2238 =item Method %s not permitted
2242 =item Missing %sbrace%s on \N{}
2244 (F) Wrong syntax of character name literal C<\N{charname}> within
2245 double-quotish context.
2247 =item Missing command in piped open
2249 (W) You used the C<open(FH, "| command")> or C<open(FH, "command |")>
2250 construction, but the command was missing or blank.
2252 =item Missing name in "my sub"
2254 (F) The reserved syntax for lexically scoped subroutines requires that they
2255 have a name with which they can be found.
2257 =item No %s specified for -%c
2259 (F) The indicated command line switch needs a mandatory argument, but
2260 you haven't specified one.
2262 =item No package name allowed for variable %s in "our"
2264 (F) Fully qualified variable names are not allowed in "our" declarations,
2265 because that doesn't make much sense under existing semantics. Such
2266 syntax is reserved for future extensions.
2268 =item No space allowed after -%c
2270 (F) The argument to the indicated command line switch must follow immediately
2271 after the switch, without intervening spaces.
2273 =item no UTC offset information; assuming local time is UTC
2275 (S) A warning peculiar to VMS. Perl was unable to find the local
2276 timezone offset, so it's assuming that local system time is equivalent
2277 to UTC. If it's not, define the logical name F<SYS$TIMEZONE_DIFFERENTIAL>
2278 to translate to the number of seconds which need to be added to UTC to
2281 =item Octal number > 037777777777 non-portable
2283 (W) The octal number you specified is larger than 2**32-1 (4294967295)
2284 and therefore non-portable between systems. See L<perlport> for more
2285 on portability concerns.
2287 See also L<perlport> for writing portable code.
2289 =item panic: del_backref
2291 (P) Failed an internal consistency check while trying to reset a weak
2294 =item panic: kid popen errno read
2296 (F) forked child returned an incomprehensible message about its errno.
2298 =item panic: magic_killbackrefs
2300 (P) Failed an internal consistency check while trying to reset all weak
2301 references to an object.
2303 =item Parentheses missing around "%s" list
2305 (W) You said something like
2311 my ($foo, $bar) = @_;
2313 Remember that "my", "our", and "local" bind tighter than comma.
2315 =item Possible Y2K bug: %s
2317 (W) You are concatenating the number 19 with another number, which
2318 could be a potential Year 2000 problem.
2320 =item Premature end of script headers
2324 =item Repeat count in pack overflows
2326 (F) You can't specify a repeat count so large that it overflows
2327 your signed integers. See L<perlfunc/pack>.
2329 =item Repeat count in unpack overflows
2331 (F) You can't specify a repeat count so large that it overflows
2332 your signed integers. See L<perlfunc/unpack>.
2334 =item realloc() of freed memory ignored
2336 (S) An internal routine called realloc() on something that had already
2339 =item Reference is already weak
2341 (W) You have attempted to weaken a reference that is already weak.
2342 Doing so has no effect.
2344 =item setpgrp can't take arguments
2346 (F) Your system has the setpgrp() from BSD 4.2, which takes no arguments,
2347 unlike POSIX setpgid(), which takes a process ID and process group ID.
2349 =item Strange *+?{} on zero-length expression
2351 (W) You applied a regular expression quantifier in a place where it
2352 makes no sense, such as on a zero-width assertion.
2353 Try putting the quantifier inside the assertion instead. For example,
2354 the way to match "abc" provided that it is followed by three
2355 repetitions of "xyz" is C</abc(?=(?:xyz){3})/>, not C</abc(?=xyz){3}/>.
2357 =item switching effective %s is not implemented
2359 (F) While under the C<use filetest> pragma, we cannot switch the
2360 real and effective uids or gids.
2362 =item This Perl can't reset CRTL environ elements (%s)
2364 =item This Perl can't set CRTL environ elements (%s=%s)
2366 (W) Warnings peculiar to VMS. You tried to change or delete an element
2367 of the CRTL's internal environ array, but your copy of Perl wasn't
2368 built with a CRTL that contained the setenv() function. You'll need to
2369 rebuild Perl with a CRTL that does, or redefine F<PERL_ENV_TABLES> (see
2370 L<perlvms>) so that the environ array isn't the target of the change to
2371 %ENV which produced the warning.
2373 =item Unknown open() mode '%s'
2375 (F) The second argument of 3-argument open() is not among the list
2376 of valid modes: C<E<lt>>, C<E<gt>>, C<E<gt>E<gt>>, C<+E<lt>>,
2377 C<+E<gt>>, C<+E<gt>E<gt>>, C<-|>, C<|E<45>>.
2379 =item Unknown process %x sent message to prime_env_iter: %s
2381 (P) An error peculiar to VMS. Perl was reading values for %ENV before
2382 iterating over it, and someone else stuck a message in the stream of
2383 data Perl expected. Someone's very confused, or perhaps trying to
2384 subvert Perl's population of %ENV for nefarious purposes.
2386 =item Unrecognized escape \\%c passed through
2388 (W) You used a backslash-character combination which is not recognized
2389 by Perl. The character was understood literally.
2391 =item Unterminated attribute parameter in attribute list
2393 (F) The lexer saw an opening (left) parenthesis character while parsing an
2394 attribute list, but the matching closing (right) parenthesis
2395 character was not found. You may need to add (or remove) a backslash
2396 character to get your parentheses to balance. See L<attributes>.
2398 =item Unterminated attribute list
2400 (F) The lexer found something other than a simple identifier at the start
2401 of an attribute, and it wasn't a semicolon or the start of a
2402 block. Perhaps you terminated the parameter list of the previous attribute
2403 too soon. See L<attributes>.
2405 =item Unterminated attribute parameter in subroutine attribute list
2407 (F) The lexer saw an opening (left) parenthesis character while parsing a
2408 subroutine attribute list, but the matching closing (right) parenthesis
2409 character was not found. You may need to add (or remove) a backslash
2410 character to get your parentheses to balance.
2412 =item Unterminated subroutine attribute list
2414 (F) The lexer found something other than a simple identifier at the start
2415 of a subroutine attribute, and it wasn't a semicolon or the start of a
2416 block. Perhaps you terminated the parameter list of the previous attribute
2419 =item Value of CLI symbol "%s" too long
2421 (W) A warning peculiar to VMS. Perl tried to read the value of an %ENV
2422 element from a CLI symbol table, and found a resultant string longer
2423 than 1024 characters. The return value has been truncated to 1024
2426 =item Version number must be a constant number
2428 (P) The attempt to translate a C<use Module n.n LIST> statement into
2429 its equivalent C<BEGIN> block found an internal inconsistency with
2434 =head1 Obsolete Diagnostics
2438 =item Character class syntax [: :] is reserved for future extensions
2440 (W) Within regular expression character classes ([]) the syntax beginning
2441 with "[:" and ending with ":]" is reserved for future extensions.
2442 If you need to represent those character sequences inside a regular
2443 expression character class, just quote the square brackets with the
2444 backslash: "\[:" and ":\]".
2446 =item Ill-formed logical name |%s| in prime_env_iter
2448 (W) A warning peculiar to VMS. A logical name was encountered when preparing
2449 to iterate over %ENV which violates the syntactic rules governing logical
2450 names. Because it cannot be translated normally, it is skipped, and will not
2451 appear in %ENV. This may be a benign occurrence, as some software packages
2452 might directly modify logical name tables and introduce nonstandard names,
2453 or it may indicate that a logical name table has been corrupted.
2455 =item Probable precedence problem on %s
2457 (W) The compiler found a bareword where it expected a conditional,
2458 which often indicates that an || or && was parsed as part of the
2459 last argument of the previous construct, for example:
2463 =item regexp too big
2465 (F) The current implementation of regular expressions uses shorts as
2466 address offsets within a string. Unfortunately this means that if
2467 the regular expression compiles to longer than 32767, it'll blow up.
2468 Usually when you want a regular expression this big, there is a better
2469 way to do it with multiple statements. See L<perlre>.
2471 =item Use of "$$<digit>" to mean "${$}<digit>" is deprecated
2473 (D) Perl versions before 5.004 misinterpreted any type marker followed
2474 by "$" and a digit. For example, "$$0" was incorrectly taken to mean
2475 "${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004.
2477 However, the developers of Perl 5.004 could not fix this bug completely,
2478 because at least two widely-used modules depend on the old meaning of
2479 "$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the
2480 old (broken) way inside strings; but it generates this message as a
2481 warning. And in Perl 5.005, this special treatment will cease.
2487 If you find what you think is a bug, you might check the
2488 articles recently posted to the comp.lang.perl.misc newsgroup.
2489 There may also be information at http://www.perl.com/perl/, the Perl
2492 If you believe you have an unreported bug, please run the B<perlbug>
2493 program included with your release. Make sure to trim your bug down
2494 to a tiny but sufficient test case. Your bug report, along with the
2495 output of C<perl -V>, will be sent off to perlbug@perl.com to be
2496 analysed by the Perl porting team.
2500 The F<Changes> file for exhaustive details on what changed.
2502 The F<INSTALL> file for how to build Perl.
2504 The F<README> file for general stuff.
2506 The F<Artistic> and F<Copying> files for copyright information.
2510 Written by Gurusamy Sarathy <F<gsar@activestate.com>>, with many
2511 contributions from The Perl Porters.
2513 Send omissions or corrections to <F<perlbug@perl.com>>.