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
8 developers only. The included sources may not even build correctly on
9 some platforms. Subscribing to perl5-porters is the best way to
10 monitor and contribute to the progress of development releases (see
11 http://www.hut.fi/~jhi/perl5-porters.html for info).
13 This document describes differences between the 5.005 release and this one.
15 =head1 Incompatible Changes
17 =head2 Perl Source Incompatibilities
19 Beware that any new warnings that have been added or old ones
20 that have been enhanced are B<not> considered incompatible changes.
22 Since all new warnings must be explicitly requested via the C<-w>
23 switch or the C<warnings> pragma, it is ultimately the programmer's
24 responsibility to ensure that warnings are enabled judiciously.
28 =item CHECK is a new keyword
30 In addition to C<BEGIN>, C<INIT>, C<END>, C<DESTROY> and C<AUTOLOAD>,
31 subroutines named C<CHECK> are now special. These are queued up during
32 compilation and behave similar to END blocks, except they are called at
33 the end of compilation rather than at the end of execution. They cannot
36 =item Treatment of list slices of undef has changed
38 When taking a slice of a literal list (as opposed to a slice of
39 an array or hash), Perl used to return an empty list if the
40 result happened to be composed of all undef values.
42 The new behavior is to produce an empty list if (and only if)
43 the original list was empty. Consider the following example:
45 @a = (1,undef,undef,2)[2,1,2];
47 The old behavior would have resulted in @a having no elements.
48 The new behavior ensures it has three undefined elements.
50 Note in particular that the behavior of slices of the following
51 cases remains unchanged:
55 @a = (anything_returning_empty_list())[2,1,2];
61 =head2 Perl's version numbering has changed
63 Beginning with Perl version 5.6, the version number convention has been
64 changed to a "dotted integer" scheme that is more commonly found in open
67 Maintenance versions of v5.6.0 will be released as v5.6.1, v5.6.2 etc.
68 The next development series following v5.6 will be numbered v5.7.x,
69 beginning with v5.7.0, and the next major production release following
72 The English module now sets $PERL_VERSION to $^V (a string value) rather
73 than C<$]> (a numeric value). (This is a potential incompatibility.
74 Send us a report via perlbug if you are affected by this.)
76 The v1.2.3 syntax is also now legal in Perl.
77 See L<Support for strings represented as a vector of ordinals> for more on that.
79 To cope with the new versioning system's use of at least three significant
80 digits for each version component, the method used for incrementing the
81 subversion number has also changed slightly. We assume that versions older
82 than v5.6 have been incrementing the subversion component in multiples of
83 10. Versions after v5.6.0 will increment them by 1. Thus, using the new
84 notation, 5.005_03 is the same as v5.5.30, and the first maintenance
85 version following v5.6.0 will be v5.6.1, which amounts to a floating point
88 =item Literals of the form C<1.2.3> parse differently
90 Previously, numeric literals with more than one dot in them were
91 interpreted as a floating point number concatenated with one or more
92 numbers. Such "numbers" are now parsed as strings composed of the
95 For example, C<print 97.98.99> used to output C<97.9899> in earlier
96 versions, but now prints C<abc>.
98 See L<Support for strings represented as a vector of ordinals> below.
100 =item Possibly changed pseudo-random number generator
102 In 5.005_0x and earlier, perl's rand() function used the C library
103 rand(3) function. As of 5.005_52, Configure tests for drand48(),
104 random(), and rand() (in that order) and picks the first one it finds.
105 Perl programs that depend on reproducing a specific set of pseudo-random
106 numbers will now likely produce different output. You can use
107 C<sh Configure -Drandfunc=rand> to obtain the old behavior.
109 =item Hashing function for hash keys has changed
111 Perl hashes are not order preserving. The apparently random order
112 encountered when iterating on the contents of a hash is determined
113 by the hashing algorithm used. To improve the distribution of lower
114 bits in the hashed value, the algorithm has changed slightly as of
115 5.005_52. When iterating over hashes, this may yield a random order
116 that is B<different> from that of previous versions.
118 =item C<undef> fails on read only values
120 Using the C<undef> operator on a readonly value (such as $1) has
121 the same effect as assigning C<undef> to the readonly value--it
124 =item Close-on-exec bit may be set on pipe and socket handles
126 On systems that support a close-on-exec flag on filehandles, the
127 flag will be set for any handles created by pipe(), socketpair(),
128 socket(), and accept(), if that is warranted by the value of $^F
129 that may be in effect. Earlier versions neglected to set the flag
130 for handles created with these operators. See L<perlfunc/pipe>,
131 L<perlfunc/socketpair>, L<perlfunc/socket>, L<perlfunc/accept>,
134 =item Writing C<"$$1"> to mean C<"${$}1"> is unsupported
136 Perl 5.004 deprecated the interpretation of C<$$1> and
137 similar within interpolated strings to mean C<$$ . "1">,
138 but still allowed it.
140 In Perl 5.6 and later, C<"$$1"> always means C<"${$1}">.
142 =item delete(), values() and C<\(%h)> operate on aliases to values, not copies
144 delete(), each(), values() and hashes in a list context return the actual
145 values in the hash, instead of copies (as they used to in earlier
146 versions). Typical idioms for using these constructs copy the
147 returned values, but this can make a significant difference when
148 creating references to the returned values.
150 Keys in the hash are still returned as copies when iterating on
153 =item vec(EXPR,OFFSET,BITS) enforces powers-of-two BITS
155 vec() generates a run-time error if the BITS argument is not
156 a valid power-of-two integer.
158 =item Text of some diagnostic output has changed
160 Most references to internal Perl operations in diagnostics
161 have been changed to be more descriptive. This may be an
162 issue for programs that may incorrectly rely on the exact
163 text of diagnostics for proper functioning.
165 =item C<%@> has been removed
167 The undocumented special variable C<%@> that used to accumulate
168 "background" errors (such as those that happen in DESTROY())
169 has been removed, because it could potentially result in memory
172 =item Parenthesized not() behaves like a list operator
174 The C<not> operator now falls under the "if it looks like a function,
175 it behaves like a function" rule.
177 As a result, the parenthesized form can be used with C<grep> and C<map>.
178 The following construct used to be a syntax error before, but it works
181 grep not($_), @things;
183 On the other hand, using C<not> with a literal list slice may not
184 work. The following previously allowed construct:
186 print not (1,2,3)[0];
188 needs to be written with additional parentheses now:
190 print not((1,2,3)[0]);
192 The behavior remains unaffected when C<not> is not followed by parentheses.
194 =item Semantics of bareword prototype C<(*)> have changed
196 Arguments prototyped as C<*> will now be visible within the subroutine
197 as either a simple scalar or as a reference to a typeglob. Perl 5.005
198 always coerced simple scalar arguments to a typeglob, which wasn't useful
199 in situations where the subroutine must distinguish between a simple
200 scalar and a typeglob. See L<perlsub/Prototypes>.
202 =head2 On 64-bit platforms the semantics of bit operators have changed
204 If your platform is either natively 64-bit or your Perl has been
205 configured to used 64-bit integers (say C<perl -V> and see what is
206 your ivsize: if it is 8, you are 64-bit) , be warned that the
207 semantics of all the bitwise numeric operators (& | ^ ~ << >>) have
208 been changed. They used to be forced to be 32 bits wide, but now in
209 the aforementioned platforms they are 64 bits wide. Most dramatically
210 this affects the unary ~: what used to be 32 bits wide, is now 64 bits
211 wide. If you depend on your integers being 32 bits wide, mask off the
212 excess bits with C<& 0xffffffff>.
216 =head2 C Source Incompatibilities
220 =item C<PERL_POLLUTE>
222 Release 5.005 grandfathered old global symbol names by providing preprocessor
223 macros for extension source compatibility. As of release 5.6, these
224 preprocessor definitions are not available by default. You need to explicitly
225 compile perl with C<-DPERL_POLLUTE> to get these definitions. For
226 extensions still using the old symbols, this option can be
227 specified via MakeMaker:
229 perl Makefile.PL POLLUTE=1
231 =item C<PERL_IMPLICIT_CONTEXT>
233 PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
234 with one of -Dusethreads, -Dusemultiplicity, or both. It is not
235 intended to be enabled by users at this time.
237 This new build option provides a set of macros for all API functions
238 such that an implicit interpreter/thread context argument is passed to
239 every API function. As a result of this, something like C<sv_setsv(foo,bar)>
240 amounts to a macro invocation that actually translates to something like
241 C<Perl_sv_setsv(my_perl,foo,bar)>. While this is generally expected
242 to not have any significant source compatibility issues, the difference
243 between a macro and a real function call will need to be considered.
245 This means that there B<is> a source compatibility issue as a result of
246 this if your extensions attempt to use pointers to any of the Perl API
249 Note that the above issue is not relevant to the default build of
250 Perl, whose interfaces continue to match those of prior versions
251 (but subject to the other options described here).
253 See L<perlguts/"The Perl API"> for detailed information on the
254 ramifications of building Perl using this option.
256 =item C<PERL_POLLUTE_MALLOC>
258 Enabling Perl's malloc in release 5.005 and earlier caused
259 the namespace of system versions of the malloc family of functions to
260 be usurped by the Perl versions, since by default they used the
263 Besides causing problems on platforms that do not allow these functions to
264 be cleanly replaced, this also meant that the system versions could not
265 be called in programs that used Perl's malloc. Previous versions of Perl
266 have allowed this behaviour to be suppressed with the HIDEMYMALLOC and
267 EMBEDMYMALLOC preprocessor definitions.
269 As of release 5.6, Perl's malloc family of functions have default names
270 distinct from the system versions. You need to explicitly compile perl with
271 C<-DPERL_POLLUTE_MALLOC> to get the older behaviour. HIDEMYMALLOC
272 and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now
275 Note that these functions do B<not> constitute Perl's memory allocation API.
276 See L<perlguts/"Memory Allocation"> for further information about that.
280 =head2 Compatible C Source API Changes
284 =item C<PATCHLEVEL> is now C<PERL_VERSION>
286 The cpp macros C<PERL_REVISION>, C<PERL_VERSION>, and C<PERL_SUBVERSION>
287 are now available by default from perl.h, and reflect the base revision,
288 patchlevel, and subversion respectively. C<PERL_REVISION> had no
289 prior equivalent, while C<PERL_VERSION> and C<PERL_SUBVERSION> were
290 previously available as C<PATCHLEVEL> and C<SUBVERSION>.
292 The new names cause less pollution of the B<cpp> namespace and reflect what
293 the numbers have come to stand for in common practice. For compatibility,
294 the old names are still supported when F<patchlevel.h> is explicitly
295 included (as required before), so there is no source incompatibility
298 =item Support for C++ exceptions
300 change#3386, also needs perlguts documentation
301 [TODO - Chip Salzenberg <chip@perlsupport.com>]
305 =head2 Binary Incompatibilities
307 In general, the default build of this release is expected to be binary
308 compatible for extensions built with the 5.005 release or its maintenance
309 versions. However, specific platforms may have broken binary compatibility
310 due to changes in the defaults used in hints files. Therefore, please be
311 sure to always check the platform-specific README files for any notes to
314 The usethreads or usemultiplicity builds are B<not> binary compatible
315 with the corresponding builds in 5.005.
317 On platforms that require an explicit list of exports (AIX, OS/2 and Windows,
318 among others), purely internal symbols such as parser functions and the
319 run time opcodes are not exported by default. Perl 5.005 used to export
320 all functions irrespective of whether they were considered part of the
323 For the full list of public API functions, see L<perlapi>.
325 =head1 Installation and Configuration Improvements
327 =head2 -Dusethreads means something different
329 WARNING: Support for threads continues to be an experimental feature.
330 Interfaces and implementation are subject to sudden and drastic changes.
332 The -Dusethreads flag now enables the experimental interpreter-based thread
333 support by default. To get the flavor of experimental threads that was in
334 5.005 instead, you need to ask for -Duse5005threads.
336 As of v5.5.640, interpreter-threads support is still lacking a way to
337 create new threads from Perl (i.e., C<use Thread;> will not work with
338 interpreter threads). C<use Thread;> continues to be available when you
339 ask for -Duse5005threads, bugs and all.
341 =head2 New Configure flags
343 The following new flags may be enabled on the Configure command line
344 by running Configure with C<-Dflag>.
349 use64bitint (equal to now deprecated 'use64bits')
355 usesocks (only SOCKS v5 supported)
357 =head2 Threadedness and 64-bitness now more daring
359 The Configure options enabling the use of threads and the use of
360 64-bitness are now more daring in the sense that they no more have an
361 explicit list of operating systems of known threads/64-bit
362 capabilities. In other words: if your operating system has the
363 necessary APIs and datatypes, you should be able just to go ahead and
364 use them, for threads by Configure -Dusethreads, and for 64 bits
365 either explicitly by Configure -Duse64bitint or implicitly if your
366 system has 64 bit wide datatypes. See also L<"64-bit support">.
370 Some platforms have "long doubles", floating point numbers of even
371 larger range than ordinary "doubles". To enable using long doubles for
372 Perl's scalars, use -Duselongdouble.
376 You can enable both -Duse64bitint and -Dlongdouble by -Dusemorebits.
377 See also L<"64-bit support">.
379 =head2 -Duselargefiles
381 Some platforms support large files, files larger than two gigabytes.
382 See L<"Large file support"> for more information.
384 =head2 installusrbinperl
386 You can use "Configure -Uinstallusrbinperl" which causes installperl
387 to skip installing perl also as /usr/bin/perl. This is useful if you
388 prefer not to modify /usr/bin for some reason or another but harmful
389 because many scripts assume to find Perl in /usr/bin/perl.
393 You can use "Configure -Dusesocks" which causes Perl to probe
394 for the SOCKS (v5, not v4) proxy protocol library,
395 http://www.socks.nec.com/
399 You can "post-edit" the Configure variables using the Configure C<-A>
400 flag. The editing happens immediately after the platform specific
401 hints files have been processed but before the actual configuration
402 process starts. Run C<Configure -h> to find out the full C<-A> syntax.
404 =head2 Enhanced Installation Directories
406 The installation structure has been enriched to improve the support
407 for maintaining multiple versions of perl, to provide locations for
408 vendor-supplied modules, scripts, and manpages, and to ease maintenance
409 of locally-added modules, scripts, and manpages. See the section on
410 Installation Directories in the INSTALL file for complete details.
411 For most users building and installing from source, the defaults should
414 If you previously used C<Configure -Dsitelib> or C<-Dsitearch> to set
415 special values for library directories, you might wish to consider using
416 the new C<-Dsiteprefix> setting instead. Also, if you wish to re-use a
417 config.sh file from an earlier version of perl, you should be sure to
418 check that Configure makes sensible choices for the new directories.
419 See INSTALL for complete details.
423 =head2 Unicode and UTF-8 support
425 Perl can optionally use UTF-8 as its internal representation for character
426 strings. The C<utf8> and C<bytes> pragmas are used to control this support
427 in the current lexical scope. See L<perlunicode>, L<utf8> and L<bytes> for
430 =head2 Interpreter cloning, threads, and concurrency
432 WARNING: This is an experimental feature in a pre-alpha state. Use
435 Perl 5.005_63 introduces the beginnings of support for running multiple
436 interpreters concurrently in different threads. In conjunction with
437 the perl_clone() API call, which can be used to selectively duplicate
438 the state of any given interpreter, it is possible to compile a
439 piece of code once in an interpreter, clone that interpreter
440 one or more times, and run all the resulting interpreters in distinct
443 On Windows, this feature is used to emulate fork() at the interpreter
444 level. See L<perlfork>.
446 This feature is still in evolution. It is eventually meant to be used
447 to selectively clone a subroutine and data reachable from that
448 subroutine in a separate interpreter and run the cloned subroutine
449 in a separate thread. Since there is no shared data between the
450 interpreters, little or no locking will be needed (unless parts of
451 the symbol table are explicitly shared). This is obviously intended
452 to be an easy-to-use replacement for the existing threads support.
454 Support for cloning interpreters and interpreter concurrency can be
455 enabled using the -Dusethreads Configure option (see win32/Makefile for
456 how to enable it on Windows.) The resulting perl executable will be
457 functionally identical to one that was built with -Dmultiplicity, but
458 the perl_clone() API call will only be available in the former.
460 -Dusethreads enables, the cpp macros USE_ITHREADS by default, which enables
461 Perl source code changes that provide a clear separation between the op tree
462 and the data it operates with. The former is considered immutable, and can
463 therefore be shared between an interpreter and all of its clones, while the
464 latter is considered local to each interpreter, and is therefore copied for
467 Note that building Perl with the -Dusemultiplicity Configure option
468 is adequate if you wish to run multiple B<independent> interpreters
469 concurrently in different threads. -Dusethreads only provides the
470 additional functionality of the perl_clone() API call and other
471 support for running B<cloned> interpreters concurrently.
473 [XXX TODO - the Compiler backends may be broken when USE_ITHREADS is
476 =head2 Lexically scoped warning categories
478 You can now control the granularity of warnings emitted by perl at a finer
479 level using the C<use warnings> pragma. See L<warnings> and L<perllexwarn>
482 =head2 Lvalue subroutines
484 WARNING: This is an experimental feature.
487 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>,
488 Tuomas Lukka <lukka@iki.fi>)]
490 =head2 "our" declarations
492 An "our" declaration introduces a value that can be best understood
493 as a lexically scoped symbolic alias to a global variable in the
494 package that was current where the variable was declared. This is
495 mostly useful as an alternative to the C<vars> pragma, but also provides
496 the opportunity to introduce typing and other attributes for such
497 variables. See L<perlfunc/our>.
499 =head2 Support for strings represented as a vector of ordinals
501 Literals of the form C<v1.2.3.4> are now parsed as a string composed of
502 of characters with the specified ordinals. This is an alternative, more
503 readable way to construct (possibly unicode) strings instead of
504 interpolating characters, as in C<"\x{1}\x{2}\x{3}\x{4}">. The leading
505 C<v> may be omitted if there are more than two ordinals, so C<1.2.3> is
506 parsed the same as C<v1.2.3>.
508 Strings written in this form are also useful to represent version "numbers".
509 It is easy to compare such version "numbers" (which are really just plain
510 strings) using any of the usual string comparison operators C<eq>, C<ne>,
511 C<lt>, C<gt>, etc., or perform bitwise string operations on them using C<|>,
514 In conjunction with the new C<$^V> magic variable (which contains
515 the perl version as a string), such literals can be used as a readable way
516 to check if you're running a particular version of Perl:
518 # this will parse in older versions of Perl also
519 if ($^V and $^V gt v5.5.640) {
520 # new features supported
523 C<require> and C<use> also have some special magic to support such literals.
524 They will be interpreted as a version rather than as a module name:
526 require v5.6.0; # croak if $^V lt v5.6.0
527 use v5.6.0; # same, but croaks at compile-time
529 Alternatively, the C<v> may be omitted if there is more than one dot:
534 Also, C<sprintf> and C<printf> support the Perl-specific format flag C<%v>
535 to print ordinals of characters in arbitrary strings:
537 printf "v%vd", $^V; # prints current version, such as "v5.5.650"
538 printf "%*vX", ":", $addr; # formats IPv6 address
539 printf "%*vb", " ", $bits; # displays bitstring
541 See L<perlop/"Strings of Character"> for additional information.
543 =head2 Weak references
545 WARNING: This is an experimental feature.
547 In previous versions of Perl, you couldn't cache objects so as
548 to allow them to be deleted if the last reference from outside
549 the cache is deleted. The reference in the cache would hold a
550 reference count on the object and the objects would never be
553 Another familiar problem is with circular references. When an
554 object references itself, its reference count would never go
555 down to zero, and it would not get destroyed until the program
558 Weak references solve this by allowing you to "weaken" any
559 reference, that is, make it not count towards the reference count.
560 When the last non-weak reference to an object is deleted, the object
561 is destroyed and all the weak references to the object are
562 automatically undef-ed.
564 To use this feature, you need the WeakRef package from CPAN, which
565 contains additional documentation.
567 change#3385, also need perlguts documentation
568 [TODO - Tuomas Lukka <lukka@iki.fi>]
570 =head2 File globbing implemented internally
572 WARNING: This is currently an experimental feature. Interfaces and
573 implementation are likely to change.
575 Perl now uses the File::Glob implementation of the glob() operator
576 automatically. This avoids using an external csh process and the
577 problems associated with it.
579 =head2 Binary numbers supported
581 Binary numbers are now supported as literals, in s?printf formats, and
585 printf "The answer is: %b\n", oct("0b101010");
587 =head2 Some arrows may be omitted in calls through references
589 Perl now allows the arrow to be omitted in many constructs
590 involving subroutine calls through references. For example,
591 C<$foo[10]-E<gt>('foo')> may now be written C<$foo[10]('foo')>.
592 This is rather similar to how the arrow may be omitted from
593 C<$foo[10]-E<gt>{'foo'}>. Note however, that the arrow is still
594 required for C<foo(10)-E<gt>('bar')>.
596 =head2 exists() is supported on subroutine names
598 The exists() builtin now works on subroutine names. A subroutine
599 is considered to exist if it has been declared (even if implicitly).
600 See L<perlfunc/exists> for examples.
602 =head2 exists() and delete() are supported on array elements
604 The exists() and delete() builtins now work on simple arrays as well.
605 The behavior is similar to that on hash elements.
607 exists() can be used to check whether an array element has been
608 initialized. This avoids autovivifying array elements that don't exist.
609 If the array is tied, the EXISTS() method in the corresponding tied
610 package will be invoked.
612 delete() may be used to remove an element from the array and return
613 it. The array element at that position returns to its unintialized
614 state, so that testing for the same element with exists() will return
615 false. If the element happens to be the one at the end, the size of
616 the array also shrinks up to the highest element that tests true for
617 exists(), or 0 if none such is found. If the array is tied, the DELETE()
618 method in the corresponding tied package will be invoked.
620 See L<perlfunc/exists> and L<perlfunc/delete> for examples.
622 =head2 syswrite() ease-of-use
624 The length argument of C<syswrite()> has become optional.
626 =head2 File and directory handles can be autovivified
628 Similar to how constructs such as C<$x-E<gt>[0]> autovivify a reference,
629 handle constructors (open(), opendir(), pipe(), socketpair(), sysopen(),
630 socket(), and accept()) now autovivify a file or directory handle
631 if the handle passed to them is an uninitialized scalar variable. This
632 allows the constructs such as C<open(my $fh, ...)> and C<open(local $fh,...)>
633 to be used to create filehandles that will conveniently be closed
634 automatically when the scope ends, provided there are no other references
635 to them. This largely eliminates the need for typeglobs when opening
636 filehandles that must be passed around, as in the following example:
640 or die "Can't open '@_': $!";
645 my $f = myopen("</etc/motd");
647 # $f implicitly closed here
650 [TODO - this idiom needs more pod penetration]
652 =head2 64-bit support
654 NOTE: The Configure flags -Duselonglong and -Duse64bits
655 have been deprecated. Use -Duse64bitint instead.
657 Any platform that has 64-bit integers either (a) natively as longs or
658 ints (b) via special compiler flags (c) using long long are able to
659 use "quads" (64-integers) as follows:
665 constants (decimal, hexadecimal, octal, binary) in the code
669 arguments to oct() and hex()
673 arguments to print(), printf() and sprintf() (flag prefixes ll, L, q)
681 pack() and unpack() "q" and "Q" formats
685 in basic arithmetics: + - * / % (NOTE: operating close to the limits
686 of the integer values may produce surprising results)
690 in bit arithmetics: & | ^ ~ << >> (NOTE: these used to be forced
699 Note that unless you have the case (a) you will have to configure
700 and compile Perl using the -Duse64bitint Configure flag.
702 There are actually two modes of 64-bitness: the first one is achieved
703 using Configure -Duse64bitint and the second one using Configure
704 -Duse64bitall. The difference is that the first one is minimal and
705 the second one maximal. The first one does only as much as is
706 required to get 64-bit integers into Perl (this may mean, for example,
707 using "long longs") while your memory may still be limited to 2
708 gigabytes (because your pointers most likely are 32-bit); the second
709 one goes all the way by attempting to switch also longs (and pointers)
710 being 64-bit. This may create an even more binary incompatible Perl
711 than -Duse64bitint: the resulting executable may not run at all in a
712 CPU-bit box, or you may have to reboot/reconfigure/rebuild your
713 operating system to be 64-bit aware.
715 Natively 64-bit systems like Alpha and Cray need neither -Duse64bitint
718 Last but not least: note that due to Perl's habit of always using
719 floating point numbers the quads are still not true integers.
720 When quads overflow their limits (0...18_446_744_073_709_551_615 unsigned,
721 -9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they
722 are silently promoted to floating point numbers, after which they will
723 start losing precision (their lower digits).
725 =head2 Large file support
727 If you have filesystems that support "large files" (files larger than
728 2 gigabytes), you may now also be able to create and access them from
729 Perl. You have to use Configure -Duselargefiles. Turning on the
730 large file support turns on also the 64-bit support on many platforms.
731 Beware that unless your filesystem also supports "sparse files" seeking
732 to umpteen petabytes may be unadvisable.
734 Note that in addition to requiring a proper file system to do large
735 files you may also need to adjust your per-process (or your
736 per-system, or per-process-group, or per-user-group) maximum filesize
737 limits before running Perl scripts that try to handle large files,
738 especially if you intend to write such files.
740 Finally, in addition to your process/process group maximum filesize
741 limits, you may have quota limits on your filesystems that stop you
742 (your user id or your user group id) from using large files.
744 Adjusting your process/user/group/file system/operating system limits
745 is outside the scope of Perl core language. For process limits, you
746 may try increasing the limits using your shell's limits/limit/ulimit
747 command before running Perl. The BSD::Resource extension (not
748 included with the standard Perl distribution) may also be of use, it
749 offers the getrlimit/setrlimit interface that can be used to adjust
750 process resource usage limits, including the maximum filesize limit.
754 In some systems you may be able to use long doubles to enhance the
755 range and precision of your double precision floating point numbers
756 (that is, Perl's numbers). Use Configure -Duselongdouble to enable
757 this support (if it is available).
761 You can "Configure -Dusemorebits" to turn on both the 64-bit support
762 and the long double support.
764 =head2 Enhanced support for sort() subroutines
766 Perl subroutines with a prototype of C<($$)> and XSUBs in general can
767 now be used as sort subroutines. In either case, the two elements to
768 be compared are passed as normal parameters in @_. See L<perlfunc/sort>.
770 For unprototyped sort subroutines, the historical behavior of passing
771 the elements to be compared as the global variables $a and $b remains
774 =head2 Better syntax checks on parenthesized unary operators
778 print defined(&foo,&bar,&baz);
779 print uc("foo","bar","baz");
782 used to be accidentally allowed in earlier versions, and produced
783 unpredictable behaviour. Some produced ancillary warnings
784 when used in this way; others silently did the wrong thing.
786 The parenthesized forms of most unary operators that expect a single
787 argument now ensure that they are not called with more than one
788 argument, making the cases shown above syntax errors. The usual
791 print defined &foo, &bar, &baz;
792 print uc "foo", "bar", "baz";
795 remains unchanged. See L<perlop>.
797 =head2 POSIX character class syntax [: :] supported
799 For example to match alphabetic characters use /[[:alpha:]]/.
800 See L<perlre> for details.
802 =head2 Improved C<qw//> operator
804 The C<qw//> operator is now evaluated at compile time into a true list
805 instead of being replaced with a run time call to C<split()>. This
806 removes the confusing misbehaviour of C<qw//> in scalar context, which
807 had inherited that behaviour from split().
811 $foo = ($bar) = qw(a b c); print "$foo|$bar\n";
813 now correctly prints "3|a", instead of "2|a".
815 =head2 pack() format 'Z' supported
817 The new format type 'Z' is useful for packing and unpacking null-terminated
818 strings. See L<perlfunc/"pack">.
820 =head2 pack() format modifier '!' supported
822 The new format type modifier '!' is useful for packing and unpacking
823 native shorts, ints, and longs. See L<perlfunc/"pack">.
825 =head2 pack() and unpack() support counted strings
827 The template character '/' can be used to specify a counted string
828 type to be packed or unpacked. See L<perlfunc/"pack">.
830 =head2 Comments in pack() templates
832 The '#' character in a template introduces a comment up to
833 end of the line. This facilitates documentation of pack()
836 =head2 $^X variables may now have names longer than one character
838 Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax
839 error. Now variable names that begin with a control character may be
840 arbitrarily long. However, for compatibility reasons, these variables
841 I<must> be written with explicit braces, as C<${^XY}> for example.
842 C<${^XYZ}> is synonymous with ${"\cXYZ"}. Variable names with more
843 than one control character, such as C<${^XY^Z}>, are illegal.
845 The old syntax has not changed. As before, `^X' may be either a
846 literal control-X character or the two-character sequence `caret' plus
847 `X'. When braces are omitted, the variable name stops after the
848 control character. Thus C<"$^XYZ"> continues to be synonymous with
849 C<$^X . "YZ"> as before.
851 As before, lexical variables may not have names beginning with control
852 characters. As before, variables whose names begin with a control
853 character are always forced to be in package `main'. All such variables
854 are reserved for future extensions, except those that begin with
855 C<^_>, which may be used by user programs and are guaranteed not to
856 acquire special meaning in any future version of Perl.
858 =head2 C<use attrs> implicit in subroutine attributes
860 Formerly, if you wanted to mark a subroutine as being a method call or
861 as requiring an automatic lock() when it is entered, you had to declare
862 that with a C<use attrs> pragma in the body of the subroutine.
863 That can now be accomplished with declaration syntax, like this:
865 sub mymethod : locked method ;
867 sub mymethod : locked method {
871 sub othermethod :locked :method ;
873 sub othermethod :locked :method {
878 (Note how only the first C<:> is mandatory, and whitespace surrounding
879 the C<:> is optional.)
881 F<AutoSplit.pm> and F<SelfLoader.pm> have been updated to keep the attributes
882 with the stubs they provide. See L<attributes>.
884 =head2 Regular expression improvements
886 change#2827,2373,2372,2365,1813,1800,4112,4158,4215,4301
887 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
889 =head2 Overloading improvements
892 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
894 =head2 open() with more than two arguments
896 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
898 =head2 Support for interpolating named characters
901 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
903 =head2 Experimental support for user-hooks in @INC
905 [TODO - Ken Fox <kfox@ford.com>]
907 =head2 C<require> and C<do> may be overridden
909 C<require> and C<do 'file'> operations may be overridden locally
910 by importing subroutines of the same name into the current package
911 (or globally by importing them into the CORE::GLOBAL:: namespace).
912 Overriding C<require> will also affect C<use>, provided the override
913 is visible at compile-time.
914 See L<perlsub/"Overriding Built-in Functions">.
916 =head2 New variable $^C reflects C<-c> switch
918 C<$^C> has a boolean value that reflects whether perl is being run
919 in compile-only mode (i.e. via the C<-c> switch). Since
920 BEGIN blocks are executed under such conditions, this variable
921 enables perl code to determine whether actions that make sense
922 only during normal running are warranted. See L<perlvar>.
924 =head2 New variable $^V contains Perl version in v5.6.0 format
926 C<$^V> contains the Perl version number as a string composed of
927 characters whose ordinals match the version numbers, so that it may
928 be used in string comparisons.
930 See C<Support for strings represented as a vector of ordinals> for an
933 =head2 Optional Y2K warnings
935 If Perl is built with the cpp macro C<PERL_Y2KWARN> defined,
936 it emits optional warnings when concatenating the number 19
939 This behavior must be specifically enabled when running Configure.
940 See F<INSTALL> and F<README.Y2K>.
942 =head1 Significant bug fixes
944 =head2 E<lt>HANDLEE<gt> on empty files
946 With C<$/> set to C<undef>, "slurping" an empty file returns a string of
947 zero length (instead of C<undef>, as it used to) the first time the
948 HANDLE is read after C<$/> is set to C<undef>. Further reads yield
951 This means that the following will append "foo" to an empty file (it used
954 perl -0777 -pi -e 's/^/foo/' empty_file
958 perl -pi -e 's/^/foo/' empty_file
960 is unchanged (it continues to leave the file empty).
962 =head2 C<eval '...'> improvements
964 Line numbers (as reflected by caller() and most diagnostics) within
965 C<eval '...'> were often incorrect when here documents were involved.
966 This has been corrected.
968 Lexical lookups for variables appearing in C<eval '...'> within
969 functions that were themselves called within an C<eval '...'> were
970 searching the wrong place for lexicals. The lexical search now
971 correctly ends at the subroutine's block boundary.
973 Parsing of here documents used to be flawed when they appeared as
974 the replacement expression in C<eval 's/.../.../e'>. This has
977 =head2 All compilation errors are true errors
979 Some "errors" encountered at compile time were by neccessity
980 generated as warnings followed by eventual termination of the
981 program. This enabled more such errors to be reported in a
982 single run, rather than causing a hard stop at the first error
983 that was encountered.
985 The mechanism for reporting such errors has been reimplemented
986 to queue compile-time errors and report them at the end of the
987 compilation as true errors rather than as warnings. This fixes
988 cases where error messages leaked through in the form of warnings
989 when code was compiled at run time using C<eval STRING>, and
990 also allows such errors to be reliably trapped using __DIE__ hooks.
992 =head2 Automatic flushing of output buffers
994 fork(), exec(), system(), qx//, and pipe open()s now flush buffers
995 of all files opened for output when the operation
996 was attempted. This mostly eliminates confusing
997 buffering mishaps suffered by users unaware of how Perl internally
1000 =head2 Better diagnostics on meaningless filehandle operations
1002 Constructs such as C<open(E<lt>FHE<gt>)> and C<close(E<lt>FHE<gt>)>
1003 are compile time errors. Attempting to read from filehandles that
1004 were opened only for writing will now produce warnings (just as
1005 writing to read-only filehandles does).
1007 =head2 Where possible, buffered data discarded from duped input filehandle
1009 C<open(NEW, "E<lt>&OLD")> now attempts to discard any data that
1010 was previously read and buffered in C<OLD> before duping the handle.
1011 On platforms where doing this is allowed, the next read operation
1012 on C<NEW> will return the same data as the corresponding operation
1013 on C<OLD>. Formerly, it would have returned the data from the start
1014 of the following disk block instead.
1016 =head2 eof() has the same old magic as <>
1018 C<eof()> would return true if no attempt to read from C<E<lt>E<gt>> had
1019 yet been made. C<eof()> has been changed to have a little magic of its
1020 own, it now opens the C<E<lt>E<gt>> files.
1022 =head2 system(), backticks and pipe open now reflect exec() failure
1024 On Unix and similar platforms, system(), qx() and open(FOO, "cmd |")
1025 etc., are implemented via fork() and exec(). When the underlying
1026 exec() fails, earlier versions did not report the error properly,
1027 since the exec() happened to be in a different process.
1029 The child process now communicates with the parent about the
1030 error in launching the external command, which allows these
1031 constructs to return with their usual error value and set $!.
1033 =head2 Implicitly closed filehandles are safer
1035 Sometimes implicitly closed filehandles (as when they are localized,
1036 and Perl automatically closes them on exiting the scope) could
1037 inadvertently set $? or $!. This has been corrected.
1039 =head2 C<(\$)> prototype and C<$foo{a}>
1041 An scalar reference prototype now correctly allows a hash or
1042 array element in that slot.
1044 =head2 Pseudo-hashes work better
1046 Dereferencing some types of reference values in a pseudo-hash,
1047 such as C<$ph-E<gt>{foo}[1]>, was accidentally disallowed. This has
1050 When applied to a pseudo-hash element, exists() now reports whether
1051 the specified value exists, not merely if the key is valid.
1053 delete() now works on pseudo-hashes. When given a pseudo-hash element
1054 or slice it deletes the values corresponding to the keys (but not the keys
1055 themselves). See L<perlref/"Pseudo-hashes: Using an array as a hash">.
1057 Pseudo-hash slices with constant keys are now optimized to array lookups
1060 The C<fields> pragma now provides ways to create pseudo-hashes, via
1061 fields::new() and fields::phash(). See L<fields>.
1063 =head2 C<goto &sub> and AUTOLOAD
1065 The C<goto &sub> construct works correctly when C<&sub> happens
1068 =head2 C<-bareword> allowed under C<use integer>
1070 The autoquoting of barewords preceded by C<-> did not work
1071 in prior versions when the C<integer> pragma was enabled.
1072 This has been fixed.
1074 =head2 Boolean assignment operators are legal lvalues
1076 Constructs such as C<($a ||= 2) += 1> are now allowed.
1078 =head2 C<sort $coderef @foo> allowed
1080 sort() did not accept a subroutine reference as the comparison
1081 function in earlier versions. This is now permitted.
1083 =head2 Failures in DESTROY()
1085 When code in a destructor threw an exception, it went unnoticed
1086 in earlier versions of Perl, unless someone happened to be
1087 looking in $@ just after the point the destructor happened to
1088 run. Such failures are now visible as warnings when warnings are
1091 =head2 Locale bugs fixed
1093 printf() and sprintf() previously reset the numeric locale
1094 back to the default "C" locale. This has been fixed.
1096 Numbers formatted according to the local numeric locale
1097 (such as using a decimal comma instead of a decimal dot) caused
1098 "isn't numeric" warnings, even while the operations accessing
1099 those numbers produced correct results. The warnings are gone.
1103 The C<eval 'return sub {...}'> construct could sometimes leak
1104 memory. This has been fixed.
1106 Operations that aren't filehandle constructors used to leak memory
1107 when used on invalid filehandles. This has been fixed.
1109 Constructs that modified C<@_> could fail to deallocate values
1110 in C<@_> and thus leak memory. This has been corrected.
1112 =head2 Spurious subroutine stubs after failed subroutine calls
1114 Perl could sometimes create empty subroutine stubs when a
1115 subroutine was not found in the package. Such cases stopped
1116 later method lookups from progressing into base packages.
1117 This has been corrected.
1119 =head2 Consistent numeric conversions
1122 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1124 =head2 Taint failures under C<-U>
1126 When running in unsafe mode, taint violations could sometimes
1127 cause silent failures. This has been fixed.
1129 =head2 END blocks and the C<-c> switch
1131 Prior versions used to run BEGIN B<and> END blocks when Perl was
1132 run in compile-only mode. Since this is typically not the expected
1133 behavior, END blocks are not executed anymore when the C<-c> switch
1136 See L<CHECK blocks> for how to run things when the compile phase ends.
1138 =head2 Potential to leak DATA filehandles
1140 Using the C<__DATA__> token creates an implicit filehandle to
1141 the file that contains the token. It is the program's
1142 responsibility to close it when it is done reading from it.
1144 This caveat is now better explained in the documentation.
1147 =head2 Diagnostics follow STDERR
1149 Diagnostic output now goes to whichever file the C<STDERR> handle
1150 is pointing at, instead of always going to the underlying C runtime
1151 library's C<stderr>.
1153 =head2 Other fixes for better diagnostics
1155 Line numbers are no longer suppressed (under most likely circumstances)
1156 during the global destruction phase.
1158 Diagnostics emitted from code running in threads other than the main
1159 thread are now accompanied by the thread ID.
1161 Embedded null characters in diagnostics now actually show up. They
1162 used to truncate the message in prior versions.
1164 $foo::a and $foo::b are now exempt from "possible typo" warnings only
1165 if sort() is encountered in package foo.
1167 Unrecognized alphabetic escapes encountered when parsing quote
1168 constructs now generate a warning, since they may take on new
1169 semantics in later versions of Perl.
1171 =head1 Performance enhancements
1173 =head2 Simple sort() using { $a <=> $b } and the like are optimized
1175 Many common sort() operations using a simple inlined block are now
1176 optimized for faster performance.
1178 =head2 Optimized assignments to lexical variables
1180 Certain operations in the RHS of assignment statements have been
1181 optimized to directly set the lexical variable on the LHS,
1182 eliminating redundant copying overheads.
1184 =head2 Method lookups optimized
1186 [TODO - Chip Salzenberg <chip@perlsupport.com>]
1188 =head2 Faster mechanism to invoke XSUBs
1191 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1193 =head2 Perl_malloc() improvements
1196 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1198 =head2 Faster subroutine calls
1200 Minor changes in how subroutine calls are handled internally
1201 provide marginal improvements in performance.
1203 =head1 Platform specific changes
1205 =head2 Additional supported platforms
1211 VM/ESA is now supported.
1215 Siemens BS2000 is now supported under the POSIX Shell.
1219 The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread
1224 GNU/Hurd is now supported.
1228 Rhapsody is now supported.
1232 EPOC is is now supported (on Psion 5).
1242 Perl now works with djgpp 2.02 (and 2.03 alpha).
1246 Environment variable names are not converted to uppercase any more.
1250 Wrong exit code from backticks now fixed.
1254 This port is still using its own builtin globbing.
1260 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1264 [TODO - Charles Bailey <bailey@newman.upenn.edu>]
1268 Site library searches failed to look for ".../site/5.XXX/lib"
1269 if ".../site/5.XXXYY/lib" wasn't found. This has been corrected.
1271 When given a pathname that consists only of a drivename, such
1272 as C<A:>, opendir() and stat() now use the current working
1273 directory for the drive rather than the drive root.
1275 The builtin XSUB functions in the Win32:: namespace are
1276 documented. See L<Win32>.
1278 $^X now contains the full path name of the running executable.
1280 A Win32::GetLongPathName() function is provided to complement
1281 Win32::GetFullPathName() and Win32::GetShortPathName(). See L<Win32>.
1283 POSIX::uname() is supported.
1285 system(1,...) now returns true process IDs rather than process
1286 handles. kill() accepts any real process id, rather than strictly
1287 return values from system(1,...).
1289 The C<Shell> module is supported.
1291 Rudimentary support for building under command.com in Windows 95
1294 Scripts are read in binary mode by default to allow ByteLoader (and
1295 the filter mechanism in general) to work properly. For compatibility,
1296 the DATA filehandle will be set to text mode if a carriage return is
1297 detected at the end of the line containing the __END__ or __DATA__
1298 token; if not, the DATA filehandle will be left open in binary mode.
1299 Earlier versions always opened the DATA filehandle in text mode.
1301 The glob() operator is implemented via the C<File::Glob> extension,
1302 which supports glob syntax of the C shell. This increases the flexibility
1303 of the glob() operator, but there may be compatibility issues for
1304 programs that relied on the older globbing syntax. If you want to
1305 preserve compatibility with the older syntax, you might want to put
1306 a C<use File::DosGlob;> in your program. For details and compatibility
1307 information, see L<File::Glob>.
1317 Compatibility tests for C<sub : attrs> vs the older C<use attrs>.
1321 IO constants (SEEK_*, _IO*).
1325 Directory-related IO methods (new, read, close, rewind, tied delete).
1327 =item lib/io_multihomed
1329 INET sockets with multi-homed hosts.
1341 Regression tests for C<my ($x,@y,%z) : attrs> and <sub : attrs>.
1345 File test operators.
1349 Verify operations that access pad objects (lexicals and temporaries).
1353 Verify C<exists &sub> operations.
1357 =head1 Modules and Pragmata
1365 While used internally by Perl as a pragma, this module also
1366 provides a way to fetch subroutine and variable attributes.
1371 The Perl Compiler suite has been extensively reworked for this
1374 [TODO - Vishal Bhatia <vishal@gol.com>,
1375 Nick Ing-Simmons <nick@ni-s.u-net.com>]
1379 The ByteLoader is a dedicated extension to generate and run
1380 Perl bytecode. See L<ByteLoader>.
1384 References can now be used.
1386 The new version also allows a leading underscore in constant names, but
1387 disallows a double leading underscore (as in "__LINE__"). Some other names
1388 are disallowed or warned against, including BEGIN, END, etc. Some names
1389 which were forced into main:: used to fail silently in some cases; now they're
1390 fatal (outside of main::) and an optional warning (inside of main::).
1391 The ability to detect whether a constant had been set with a given name has
1399 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1403 A C<Maxdepth> setting can be specified to avoid venturing
1404 too deeply into deep data structures. See L<Data::Dumper>.
1406 Dumping C<qr//> objects works correctly.
1410 C<DB> is an experimental module that exposes a clean abstraction
1411 to Perl's debugging API.
1415 DB_File can now be built with Berkeley DB versions 1, 2 or 3.
1416 See C<ext/DB_File/Changes>.
1420 Devel::DProf, a Perl source code profiler has been added. See
1421 L<Devel::DProf> and L<dprofpp>.
1425 The Dumpvalue module provides screen dumps of Perl data.
1429 Overall, Benchmark results exhibit lower average error and better timing
1432 You can now run tests for I<n> seconds instead of guessing the right
1433 number of tests to run: e.g. timethese(-5, ...) will run each
1434 code for at least 5 CPU seconds. Zero as the "number of repetitions"
1435 means "for at least 3 CPU seconds". The output format has also
1436 changed. For example:
1438 use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
1440 will now output something like this:
1442 Benchmark: running a, b, each for at least 5 CPU seconds...
1443 a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
1444 b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
1446 New features: "each for at least N CPU seconds...", "wallclock secs",
1447 and the "@ operations/CPU second (n=operations)".
1449 timethese() now returns a reference to a hash of Benchmark objects containing
1450 the test results, keyed on the names of the tests.
1452 timethis() now returns the iterations field in the Benchmark result object
1455 timethese(), timethis(), and the new cmpthese() (see below) can also take
1456 a format specifier of 'none' to suppress output.
1458 A new function countit() is just like timeit() except that it takes a
1459 TIME instead of a COUNT.
1461 A new function cmpthese() prints a chart comparing the results of each test
1462 returned from a timethese() call. For each possible pair of tests, the
1463 percentage speed difference (iters/sec or seconds/iter) is shown.
1465 For other details, see L<Benchmark>.
1469 The Devel::Peek module provides access to the internal representation
1470 of Perl variables and data. It is a data debugging tool for the XS programmer.
1474 $PERL_VERSION now stands for C<$^V> (a string value) rather than for C<$]>
1477 =item ExtUtils::MakeMaker
1479 change#4135, also needs docs in module pod
1480 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1484 More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for
1485 large file (more than 4GB) access Note that the O_LARGEFILE is
1486 automatically/transparently added to sysopen() flags if large file
1487 support has been configured), Free/Net/OpenBSD locking behaviour flags
1488 F_FLOCK, F_POSIX, Linux F_SHLCK, and O_ACCMODE: the combined mask of
1489 O_RDONLY, O_WRONLY, and O_RDWR. The seek()/sysseek() constants
1490 SEEK_SET, SEEK_CUR, and SEEK_END are available via the C<:seek> tag.
1491 The chmod()/stat() S_IF* constants and S_IS* functions are available
1492 via the C<:mode> tag.
1497 A compare_text() function has been added, which allows custom
1498 comparison functions. See L<File::Compare>.
1502 File::Find now works correctly when the wanted() function is either
1503 autoloaded or is a symbolic reference.
1505 A bug that caused File::Find to lose track of the working directory
1506 when pruning top-level directories has been fixed.
1508 File::Find now also supports several other options to control its
1509 behavior. It can follow symbolic links if the C<follow> option is
1510 specified. Enabling the C<no_chdir> option will make File::Find skip
1511 changing the current directory when walking directories. The C<untaint>
1512 flag can be useful when running with taint checks enabled.
1518 This extension implements BSD-style file globbing. By default,
1519 it will also be used for the internal implementation of the glob()
1520 operator. See L<File::Glob>.
1524 New methods have been added to the File::Spec module: devnull() returns
1525 the name of the null device (/dev/null on Unix) and tmpdir() the name of
1526 the temp directory (normally /tmp on Unix). There are now also methods
1527 to convert between absolute and relative filenames: abs2rel() and
1528 rel2abs(). For compatibility with operating systems that specify volume
1529 names in file paths, the splitpath(), splitdir(), and catdir() methods
1532 =item File::Spec::Functions
1534 The new File::Spec::Functions modules provides a function interface
1535 to the File::Spec module. Allows shorthand
1537 $fullname = catfile($dir1, $dir2, $file);
1541 $fullname = File::Spec->catfile($dir1, $dir2, $file);
1545 Getopt::Long licensing has changed to allow the Perl Artistic License
1546 as well as the GPL. It used to be GPL only, which got in the way of
1547 non-GPL applications that wanted to use Getopt::Long.
1549 Getopt::Long encourages the use of Pod::Usage to produce help
1550 messages. For example:
1556 GetOptions('help|?' => \$help, man => \$man) or pod2usage(2);
1557 pod2usage(1) if $help;
1558 pod2usage(-exitstatus => 0, -verbose => 2) if $man;
1564 sample - Using GetOpt::Long and Pod::Usage
1568 sample [options] [file ...]
1571 -help brief help message
1572 -man full documentation
1580 Print a brief help message and exits.
1584 Prints the manual page and exits.
1590 B<This program> will read the given input file(s) and do someting
1591 useful with the contents thereof.
1595 See L<Pod::Usage> for details.
1597 A bug that prevented the non-option call-back E<lt>E<gt> from being
1598 specified as the first argument has been fixed.
1600 To specify the characters E<lt> and E<gt> as option starters, use
1601 E<gt>E<lt>. Note, however, that changing option starters is strongly
1606 write() and syswrite() will now accept a single-argument
1607 form of the call, for consistency with Perl's syswrite().
1609 You can now create a TCP-based IO::Socket::INET without forcing
1610 a connect attempt. This allows you to configure its options
1611 (like making it non-blocking) and then call connect() manually.
1613 A bug that prevented the IO::Socket::protocol() accessor
1614 from ever returning the correct value has been corrected.
1618 Java Perl Lingo is now distributed with Perl. See jpl/README
1619 for more information.
1623 C<use lib> now weeds out any trailing duplicate entries.
1624 C<no lib> removes all named entries.
1628 The bitwise operations C<E<lt>E<lt>>, C<E<gt>E<gt>>, C<&>, C<|>,
1629 and C<~> are now supported on bigints.
1633 The accessor methods Re, Im, arg, abs, rho, and theta can now also
1634 act as mutators (accessor $z->Re(), mutator $z->Re(3)).
1638 A little bit of radial trigonometry (cylindrical and spherical),
1639 radial coordinate conversions, and the great circle distance were added.
1641 =item Pod::Parser, Pod::InputObjects
1643 Pod::Parser is a base class for parsing and selecting sections of
1644 pod documentation from an input stream. This module takes care of
1645 identifying pod paragraphs and commands in the input and hands off the
1646 parsed paragraphs and commands to user-defined methods which are free
1647 to interpret or translate them as they see fit.
1649 Pod::InputObjects defines some input objects needed by Pod::Parser, and
1650 for advanced users of Pod::Parser that need more about a command besides
1653 As of release 5.6 of Perl, Pod::Parser is now the officially sanctioned
1654 "base parser code" recommended for use by all pod2xxx translators.
1655 Pod::Text (pod2text) and Pod::Man (pod2man) have already been converted
1656 to use Pod::Parser and efforts to convert Pod::HTML (pod2html) are already
1657 underway. For any questions or comments about pod parsing and translating
1658 issues and utilities, please use the pod-people@perl.org mailing list.
1660 For further information, please see L<Pod::Parser> and L<Pod::InputObjects>.
1662 =item Pod::Checker, podchecker
1664 This utility checks pod files for correct syntax, according to
1665 L<perlpod>. Obvious errors are flagged as such, while warnings are
1666 printed for mistakes that can be handled gracefully. The checklist is
1667 not complete yet. See L<Pod::Checker>.
1669 =item Pod::ParseUtils, Pod::Find
1671 These modules provide a set of gizmos that are useful mainly for pod
1672 translators. L<Pod::Find|Pod::Find> traverses directory structures and
1673 returns found pod files, along with their canonical names (like
1674 C<File::Spec::Unix>). L<Pod::ParseUtils|Pod::ParseUtils> contains
1675 B<Pod::List> (useful for storing pod list information), B<Pod::Hyperlink>
1676 (for parsing the contents of C<LE<gt>E<lt>> sequences) and B<Pod::Cache>
1677 (for caching information about pod files, e.g. link nodes).
1679 =item Pod::Select, podselect
1681 Pod::Select is a subclass of Pod::Parser which provides a function
1682 named "podselect()" to filter out user-specified sections of raw pod
1683 documentation from an input stream. podselect is a script that provides
1684 access to Pod::Select from other scripts to be used as a filter.
1687 =item Pod::Usage, pod2usage
1689 Pod::Usage provides the function "pod2usage()" to print usage messages for
1690 a Perl script based on its embedded pod documentation. The pod2usage()
1691 function is generally useful to all script authors since it lets them
1692 write and maintain a single source (the pods) for documentation, thus
1693 removing the need to create and maintain redundant usage message text
1694 consisting of information already in the pods.
1696 There is also a pod2usage script which can be used from other kinds of
1697 scripts to print usage messages from pods (even for non-Perl scripts
1698 with pods embedded in comments).
1700 For details and examples, please see L<Pod::Usage>.
1702 =item Pod::Text and Pod::Man
1704 [TODO - Russ Allbery <rra@stanford.edu>]
1708 An EXISTS method has been added to this module (and sdbm_exists() has
1709 been added to the underlying sdbm library), so one can now call exists
1710 on an SDBM_File tied hash and get the correct result, rather than a
1713 A bug that may have caused data loss when more than one disk block
1714 happens to be read from the database in a single FETCH() has been
1719 Sys::Syslog now uses XSUBs to access facilities from syslog.h so it
1720 no longer requires syslog.ph to exist.
1724 Sys::Hostname now uses XSUBs to call the C library's gethostname() or
1725 uname() if they exist.
1729 The timelocal() and timegm() functions used to silently return bogus
1730 results when the date fell outside the machine's integer range. They
1731 now consistently croak() if the date falls in an unsupported range.
1735 The error return value in list context has been changed for all functions
1736 that return a list of values. Previously these functions returned a list
1737 with a single element C<undef> if an error occurred. Now these functions
1738 return the empty list in these situations. This applies to the following
1744 The remaining functions are unchanged and continue to return C<undef> on
1745 error even in list context.
1747 The Win32::SetLastError(ERROR) function has been added as a complement
1748 to the Win32::GetLastError() function.
1750 The new Win32::GetFullPathName(FILENAME) returns the full absolute
1751 pathname for FILENAME in scalar context. In list context it returns
1752 a two-element list containing the fully qualified directory name and
1753 the filename. See L<Win32>.
1757 A new feature called "DBM Filters" has been added to all the
1758 DBM modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File.
1759 DBM Filters add four new methods to each DBM module:
1766 These can be used to filter key-value pairs before the pairs are
1767 written to the database or just after they are read from the database.
1768 See L<perldbmfilter> for further information.
1774 C<use attrs> is now obsolete, and is only provided for
1775 backward-compatibility. It's been replaced by the C<sub : attributes>
1776 syntax. See L<perlsub/"Subroutine Attributes"> and L<attributes>.
1778 C<use utf8> to enable UTF-8 and Unicode support.
1780 Lexical warnings pragma, C<use warnings;>, to control optional warnings.
1783 C<use filetest> to control the behaviour of filetests (C<-r> C<-w>
1784 ...). Currently only one subpragma implemented, "use filetest
1785 'access';", that uses access(2) or equivalent to check permissions
1786 instead of using stat(2) as usual. This matters in filesystems
1787 where there are ACLs (access control lists): the stat(2) might lie,
1788 but access(2) knows better.
1790 =head1 Utility Changes
1794 [TODO - Kurt Starsinic <kstar@chapin.edu>]
1798 C<perlcc> now supports the C and Bytecode backends. By default,
1799 it generates output from the simple C backend rather than the
1800 optimized C backend.
1802 Support for non-Unix platforms has been improved.
1807 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1809 =head1 Documentation Changes
1815 The official list of public Perl API functions.
1817 =item perlcompile.pod
1819 An introduction to using the Perl Compiler suite.
1821 =item perlfilter.pod
1823 An introduction to writing Perl source filters.
1827 Some guidelines for hacking the Perl source code.
1829 =item perlintern.pod
1831 A list of internal functions in the Perl source code.
1832 (List is currently empty.)
1834 =item perlopentut.pod
1836 A tutorial on using open() effectively.
1838 =item perlreftut.pod
1840 A tutorial that introduces the essentials of references.
1844 A tutorial on managing class data for object modules.
1846 =item perlunicode.pod
1848 An introduction to Unicode support features in Perl.
1852 =head1 New or Changed Diagnostics
1856 =item "%s" variable %s masks earlier declaration in same %s
1858 (W) A "my" or "our" variable has been redeclared in the current scope or statement,
1859 effectively eliminating all access to the previous instance. This is almost
1860 always a typographical error. Note that the earlier variable will still exist
1861 until the end of the scope or until all closure referents to it are
1864 =item "my sub" not yet implemented
1866 (F) Lexically scoped subroutines are not yet implemented. Don't try that
1869 =item "our" variable %s redeclared
1871 (W) You seem to have already declared the same global once before in the
1872 current lexical scope.
1874 =item '!' allowed only after types %s
1876 (F) The '!' is allowed in pack() and unpack() only after certain types.
1877 See L<perlfunc/pack>.
1879 =item / cannot take a count
1881 (F) You had an unpack template indicating a counted-length string,
1882 but you have also specified an explicit size for the string.
1883 See L<perlfunc/pack>.
1885 =item / must be followed by a, A or Z
1887 (F) You had an unpack template indicating a counted-length string,
1888 which must be followed by one of the letters a, A or Z
1889 to indicate what sort of string is to be unpacked.
1890 See L<perlfunc/pack>.
1892 =item / must be followed by a*, A* or Z*
1894 (F) You had a pack template indicating a counted-length string,
1895 Currently the only things that can have their length counted are a*, A* or Z*.
1896 See L<perlfunc/pack>.
1898 =item / must follow a numeric type
1900 (F) You had an unpack template that contained a '#',
1901 but this did not follow some numeric unpack specification.
1902 See L<perlfunc/pack>.
1904 =item /%s/: Unrecognized escape \\%c passed through
1906 (W) You used a backslash-character combination which is not recognized
1907 by Perl. This combination appears in an interpolated variable or a
1908 C<'>-delimited regular expression. The character was understood literally.
1910 =item /%s/: Unrecognized escape \\%c in character class passed through
1912 (W) You used a backslash-character combination which is not recognized
1913 by Perl inside character classes. The character was understood literally.
1915 =item /%s/ should probably be written as "%s"
1917 (W) You have used a pattern where Perl expected to find a string,
1918 as in the first argument to C<join>. Perl will treat the true
1919 or false result of matching the pattern against $_ as the string,
1920 which is probably not what you had in mind.
1922 =item %s() called too early to check prototype
1924 (W) You've called a function that has a prototype before the parser saw a
1925 definition or declaration for it, and Perl could not check that the call
1926 conforms to the prototype. You need to either add an early prototype
1927 declaration for the subroutine in question, or move the subroutine
1928 definition ahead of the call to get proper prototype checking. Alternatively,
1929 if you are certain that you're calling the function correctly, you may put
1930 an ampersand before the name to avoid the warning. See L<perlsub>.
1932 =item %s argument is not a HASH or ARRAY element
1934 (F) The argument to exists() must be a hash or array element, such as:
1937 $ref->[12]->["susie"]
1939 =item %s argument is not a HASH or ARRAY element or slice
1941 (F) The argument to delete() must be either a hash or array element, such as:
1944 $ref->[12]->["susie"]
1946 or a hash or array slice, such as:
1948 @foo[$bar, $baz, $xyzzy]
1949 @{$ref->[12]}{"susie", "queue"}
1951 =item %s argument is not a subroutine name
1953 (F) The argument to exists() for C<exists &sub> must be a subroutine
1954 name, and not a subroutine call. C<exists &sub()> will generate this error.
1956 =item %s package attribute may clash with future reserved word: %s
1958 (W) A lowercase attribute name was used that had a package-specific handler.
1959 That name might have a meaning to Perl itself some day, even though it
1960 doesn't yet. Perhaps you should use a mixed-case attribute name, instead.
1963 =item (in cleanup) %s
1965 (W) This prefix usually indicates that a DESTROY() method raised
1966 the indicated exception. Since destructors are usually called by
1967 the system at arbitrary points during execution, and often a vast
1968 number of times, the warning is issued only once for any number
1969 of failures that would otherwise result in the same message being
1972 Failure of user callbacks dispatched using the C<G_KEEPERR> flag
1973 could also result in this warning. See L<perlcall/G_KEEPERR>.
1975 =item <> should be quotes
1977 (F) You wrote C<require E<lt>fileE<gt>> when you should have written
1980 =item Attempt to join self
1982 (F) You tried to join a thread from within itself, which is an
1983 impossible task. You may be joining the wrong thread, or you may
1984 need to move the join() to some other thread.
1986 =item Bad evalled substitution pattern
1988 (F) You've used the /e switch to evaluate the replacement for a
1989 substitution, but perl found a syntax error in the code to evaluate,
1990 most likely an unexpected right brace '}'.
1992 =item Bad realloc() ignored
1994 (S) An internal routine called realloc() on something that had never been
1995 malloc()ed in the first place. Mandatory, but can be disabled by
1996 setting environment variable C<PERL_BADFREE> to 1.
1998 =item Bareword found in conditional
2000 (W) The compiler found a bareword where it expected a conditional,
2001 which often indicates that an || or && was parsed as part of the
2002 last argument of the previous construct, for example:
2006 It may also indicate a misspelled constant that has been interpreted
2009 use constant TYPO => 1;
2010 if (TYOP) { print "foo" }
2012 The C<strict> pragma is useful in avoiding such errors.
2014 =item Binary number > 0b11111111111111111111111111111111 non-portable
2016 (W) The binary number you specified is larger than 2**32-1
2017 (4294967295) and therefore non-portable between systems. See
2018 L<perlport> for more on portability concerns.
2020 =item Bit vector size > 32 non-portable
2022 (W) Using bit vector sizes larger than 32 is non-portable.
2024 =item Buffer overflow in prime_env_iter: %s
2026 (W) A warning peculiar to VMS. While Perl was preparing to iterate over
2027 %ENV, it encountered a logical name or symbol definition which was too long,
2028 so it was truncated to the string shown.
2030 =item Can't check filesystem of script "%s"
2032 (P) For some reason you can't check the filesystem of the script for nosuid.
2034 =item Can't declare class for non-scalar %s in "%s"
2036 (S) Currently, only scalar variables can declared with a specific class
2037 qualifier in a "my" or "our" declaration. The semantics may be extended
2038 for other types of variables in future.
2040 =item Can't declare %s in "%s"
2042 (F) Only scalar, array, and hash variables may be declared as "my" or
2043 "our" variables. They must have ordinary identifiers as names.
2045 =item Can't ignore signal CHLD, forcing to default
2047 (W) Perl has detected that it is being run with the SIGCHLD signal
2048 (sometimes known as SIGCLD) disabled. Since disabling this signal
2049 will interfere with proper determination of exit status of child
2050 processes, Perl has reset the signal to its default value.
2051 This situation typically indicates that the parent program under
2052 which Perl may be running (e.g. cron) is being very careless.
2054 =item Can't modify non-lvalue subroutine call
2056 (F) Subroutines meant to be used in lvalue context should be declared as
2057 such, see L<perlsub/"Lvalue subroutines">.
2059 =item Can't read CRTL environ
2061 (S) A warning peculiar to VMS. Perl tried to read an element of %ENV
2062 from the CRTL's internal environment array and discovered the array was
2063 missing. You need to figure out where your CRTL misplaced its environ
2064 or define F<PERL_ENV_TABLES> (see L<perlvms>) so that environ is not searched.
2066 =item Can't remove %s: %s, skipping file
2068 (S) You requested an inplace edit without creating a backup file. Perl
2069 was unable to remove the original file to replace it with the modified
2070 file. The file was left unmodified.
2072 =item Can't return %s from lvalue subroutine
2074 (F) Perl detected an attempt to return illegal lvalues (such
2075 as temporary or readonly values) from a subroutine used as an lvalue.
2076 This is not allowed.
2078 =item Can't weaken a nonreference
2080 (F) You attempted to weaken something that was not a reference. Only
2081 references can be weakened.
2083 =item Character class [:%s:] unknown
2085 (F) The class in the character class [: :] syntax is unknown.
2088 =item Character class syntax [%s] belongs inside character classes
2090 (W) The character class constructs [: :], [= =], and [. .] go
2091 I<inside> character classes, the [] are part of the construct,
2092 for example: /[012[:alpha:]345]/. Note that [= =] and [. .]
2093 are not currently implemented; they are simply placeholders for
2096 =item Constant is not %s reference
2098 (F) A constant value (perhaps declared using the C<use constant> pragma)
2099 is being dereferenced, but it amounts to the wrong type of reference. The
2100 message indicates the type of reference that was expected. This usually
2101 indicates a syntax error in dereferencing the constant value.
2102 See L<perlsub/"Constant Functions"> and L<constant>.
2104 =item constant(%s): %%^H is not localized
2106 (F) When setting compile-time-lexicalized hash %^H one should set the
2107 corresponding bit of $^H as well.
2109 =item constant(%s): %s
2111 (F) Compile-time-substitutions (such as overloaded constants and
2112 character names) were not correctly set up.
2114 =item defined(@array) is deprecated
2116 (D) defined() is not usually useful on arrays because it checks for an
2117 undefined I<scalar> value. If you want to see if the array is empty,
2118 just use C<if (@array) { # not empty }> for example.
2120 =item defined(%hash) is deprecated
2122 (D) defined() is not usually useful on hashes because it checks for an
2123 undefined I<scalar> value. If you want to see if the hash is empty,
2124 just use C<if (%hash) { # not empty }> for example.
2126 =item Did not produce a valid header
2130 =item Did you mean "local" instead of "our"?
2132 (W) Remember that "our" does not localize the declared global variable.
2133 You have declared it again in the same lexical scope, which seems superfluous.
2135 =item Document contains no data
2139 =item entering effective %s failed
2141 (F) While under the C<use filetest> pragma, switching the real and
2142 effective uids or gids failed.
2144 =item false [] range "%s" in regexp
2146 (W) A character class range must start and end at a literal character, not
2147 another character class like C<\d> or C<[:alpha:]>. The "-" in your false
2148 range is interpreted as a literal "-". Consider quoting the "-", "\-".
2151 =item Filehandle %s opened only for output
2153 (W) You tried to read from a filehandle opened only for writing. If you
2154 intended it to be a read/write filehandle, you needed to open it with
2155 "+E<lt>" or "+E<gt>" or "+E<gt>E<gt>" instead of with "E<lt>" or nothing. If
2156 you intended only to read from the file, use "E<lt>". See
2159 =item flock() on closed filehandle %s
2161 (W) The filehandle you're attempting to flock() got itself closed some
2162 time before now. Check your logic flow. flock() operates on filehandles.
2163 Are you attempting to call flock() on a dirhandle by the same name?
2165 =item Global symbol "%s" requires explicit package name
2167 (F) You've said "use strict vars", which indicates that all variables
2168 must either be lexically scoped (using "my"), declared beforehand using
2169 "our", or explicitly qualified to say which package the global variable
2172 =item Hexadecimal number > 0xffffffff non-portable
2174 (W) The hexadecimal number you specified is larger than 2**32-1
2175 (4294967295) and therefore non-portable between systems. See
2176 L<perlport> for more on portability concerns.
2178 =item Ill-formed CRTL environ value "%s"
2180 (W) A warning peculiar to VMS. Perl tried to read the CRTL's internal
2181 environ array, and encountered an element without the C<=> delimiter
2182 used to spearate keys from values. The element is ignored.
2184 =item Ill-formed message in prime_env_iter: |%s|
2186 (W) A warning peculiar to VMS. Perl tried to read a logical name
2187 or CLI symbol definition when preparing to iterate over %ENV, and
2188 didn't see the expected delimiter between key and value, so the
2191 =item Illegal binary digit %s
2193 (F) You used a digit other than 0 or 1 in a binary number.
2195 =item Illegal binary digit %s ignored
2197 (W) You may have tried to use a digit other than 0 or 1 in a binary number.
2198 Interpretation of the binary number stopped before the offending digit.
2200 =item Illegal number of bits in vec
2202 (F) The number of bits in vec() (the third argument) must be a power of
2203 two from 1 to 32 (or 64, if your platform supports that).
2205 =item Integer overflow in %s number
2207 (W) The hexadecimal, octal or binary number you have specified either
2208 as a literal or as an argument to hex() or oct() is too big for your
2209 architecture, and has been converted to a floating point number. On a
2210 32-bit architecture the largest hexadecimal, octal or binary number
2211 representable without overflow is 0xFFFFFFFF, 037777777777, or
2212 0b11111111111111111111111111111111 respectively. Note that Perl
2213 transparently promotes all numbers to a floating point representation
2214 internally--subject to loss of precision errors in subsequent
2217 =item Invalid %s attribute: %s
2219 The indicated attribute for a subroutine or variable was not recognized
2220 by Perl or by a user-supplied handler. See L<attributes>.
2222 =item Invalid %s attributes: %s
2224 The indicated attributes for a subroutine or variable were not recognized
2225 by Perl or by a user-supplied handler. See L<attributes>.
2227 =item invalid [] range "%s" in regexp
2229 The offending range is now explicitly displayed.
2231 =item Invalid separator character %s in attribute list
2233 (F) Something other than a colon or whitespace was seen between the
2234 elements of an attribute list. If the previous attribute
2235 had a parenthesised parameter list, perhaps that list was terminated
2236 too soon. See L<attributes>.
2238 =item Invalid separator character %s in subroutine attribute list
2240 (F) Something other than a colon or whitespace was seen between the
2241 elements of a subroutine attribute list. If the previous attribute
2242 had a parenthesised parameter list, perhaps that list was terminated
2245 =item leaving effective %s failed
2247 (F) While under the C<use filetest> pragma, switching the real and
2248 effective uids or gids failed.
2250 =item Lvalue subs returning %s not implemented yet
2252 (F) Due to limitations in the current implementation, array and hash
2253 values cannot be returned in subroutines used in lvalue context.
2254 See L<perlsub/"Lvalue subroutines">.
2256 =item Method %s not permitted
2260 =item Missing %sbrace%s on \N{}
2262 (F) Wrong syntax of character name literal C<\N{charname}> within
2263 double-quotish context.
2265 =item Missing command in piped open
2267 (W) You used the C<open(FH, "| command")> or C<open(FH, "command |")>
2268 construction, but the command was missing or blank.
2270 =item Missing name in "my sub"
2272 (F) The reserved syntax for lexically scoped subroutines requires that they
2273 have a name with which they can be found.
2275 =item No %s specified for -%c
2277 (F) The indicated command line switch needs a mandatory argument, but
2278 you haven't specified one.
2280 =item No package name allowed for variable %s in "our"
2282 (F) Fully qualified variable names are not allowed in "our" declarations,
2283 because that doesn't make much sense under existing semantics. Such
2284 syntax is reserved for future extensions.
2286 =item No space allowed after -%c
2288 (F) The argument to the indicated command line switch must follow immediately
2289 after the switch, without intervening spaces.
2291 =item no UTC offset information; assuming local time is UTC
2293 (S) A warning peculiar to VMS. Perl was unable to find the local
2294 timezone offset, so it's assuming that local system time is equivalent
2295 to UTC. If it's not, define the logical name F<SYS$TIMEZONE_DIFFERENTIAL>
2296 to translate to the number of seconds which need to be added to UTC to
2299 =item Octal number > 037777777777 non-portable
2301 (W) The octal number you specified is larger than 2**32-1 (4294967295)
2302 and therefore non-portable between systems. See L<perlport> for more
2303 on portability concerns.
2305 See also L<perlport> for writing portable code.
2307 =item panic: del_backref
2309 (P) Failed an internal consistency check while trying to reset a weak
2312 =item panic: kid popen errno read
2314 (F) forked child returned an incomprehensible message about its errno.
2316 =item panic: magic_killbackrefs
2318 (P) Failed an internal consistency check while trying to reset all weak
2319 references to an object.
2321 =item Parentheses missing around "%s" list
2323 (W) You said something like
2329 my ($foo, $bar) = @_;
2331 Remember that "my", "our", and "local" bind tighter than comma.
2333 =item Possible Y2K bug: %s
2335 (W) You are concatenating the number 19 with another number, which
2336 could be a potential Year 2000 problem.
2338 =item Premature end of script headers
2342 =item Repeat count in pack overflows
2344 (F) You can't specify a repeat count so large that it overflows
2345 your signed integers. See L<perlfunc/pack>.
2347 =item Repeat count in unpack overflows
2349 (F) You can't specify a repeat count so large that it overflows
2350 your signed integers. See L<perlfunc/unpack>.
2352 =item realloc() of freed memory ignored
2354 (S) An internal routine called realloc() on something that had already
2357 =item Reference is already weak
2359 (W) You have attempted to weaken a reference that is already weak.
2360 Doing so has no effect.
2362 =item setpgrp can't take arguments
2364 (F) Your system has the setpgrp() from BSD 4.2, which takes no arguments,
2365 unlike POSIX setpgid(), which takes a process ID and process group ID.
2367 =item Strange *+?{} on zero-length expression
2369 (W) You applied a regular expression quantifier in a place where it
2370 makes no sense, such as on a zero-width assertion.
2371 Try putting the quantifier inside the assertion instead. For example,
2372 the way to match "abc" provided that it is followed by three
2373 repetitions of "xyz" is C</abc(?=(?:xyz){3})/>, not C</abc(?=xyz){3}/>.
2375 =item switching effective %s is not implemented
2377 (F) While under the C<use filetest> pragma, we cannot switch the
2378 real and effective uids or gids.
2380 =item This Perl can't reset CRTL environ elements (%s)
2382 =item This Perl can't set CRTL environ elements (%s=%s)
2384 (W) Warnings peculiar to VMS. You tried to change or delete an element
2385 of the CRTL's internal environ array, but your copy of Perl wasn't
2386 built with a CRTL that contained the setenv() function. You'll need to
2387 rebuild Perl with a CRTL that does, or redefine F<PERL_ENV_TABLES> (see
2388 L<perlvms>) so that the environ array isn't the target of the change to
2389 %ENV which produced the warning.
2391 =item Unknown open() mode '%s'
2393 (F) The second argument of 3-argument open() is not among the list
2394 of valid modes: C<E<lt>>, C<E<gt>>, C<E<gt>E<gt>>, C<+E<lt>>,
2395 C<+E<gt>>, C<+E<gt>E<gt>>, C<-|>, C<|E<45>>.
2397 =item Unknown process %x sent message to prime_env_iter: %s
2399 (P) An error peculiar to VMS. Perl was reading values for %ENV before
2400 iterating over it, and someone else stuck a message in the stream of
2401 data Perl expected. Someone's very confused, or perhaps trying to
2402 subvert Perl's population of %ENV for nefarious purposes.
2404 =item Unrecognized escape \\%c passed through
2406 (W) You used a backslash-character combination which is not recognized
2407 by Perl. The character was understood literally.
2409 =item Unterminated attribute parameter in attribute list
2411 (F) The lexer saw an opening (left) parenthesis character while parsing an
2412 attribute list, but the matching closing (right) parenthesis
2413 character was not found. You may need to add (or remove) a backslash
2414 character to get your parentheses to balance. See L<attributes>.
2416 =item Unterminated attribute list
2418 (F) The lexer found something other than a simple identifier at the start
2419 of an attribute, and it wasn't a semicolon or the start of a
2420 block. Perhaps you terminated the parameter list of the previous attribute
2421 too soon. See L<attributes>.
2423 =item Unterminated attribute parameter in subroutine attribute list
2425 (F) The lexer saw an opening (left) parenthesis character while parsing a
2426 subroutine attribute list, but the matching closing (right) parenthesis
2427 character was not found. You may need to add (or remove) a backslash
2428 character to get your parentheses to balance.
2430 =item Unterminated subroutine attribute list
2432 (F) The lexer found something other than a simple identifier at the start
2433 of a subroutine attribute, and it wasn't a semicolon or the start of a
2434 block. Perhaps you terminated the parameter list of the previous attribute
2437 =item Value of CLI symbol "%s" too long
2439 (W) A warning peculiar to VMS. Perl tried to read the value of an %ENV
2440 element from a CLI symbol table, and found a resultant string longer
2441 than 1024 characters. The return value has been truncated to 1024
2444 =item Version number must be a constant number
2446 (P) The attempt to translate a C<use Module n.n LIST> statement into
2447 its equivalent C<BEGIN> block found an internal inconsistency with
2452 =head1 Obsolete Diagnostics
2456 =item Character class syntax [: :] is reserved for future extensions
2458 (W) Within regular expression character classes ([]) the syntax beginning
2459 with "[:" and ending with ":]" is reserved for future extensions.
2460 If you need to represent those character sequences inside a regular
2461 expression character class, just quote the square brackets with the
2462 backslash: "\[:" and ":\]".
2464 =item Ill-formed logical name |%s| in prime_env_iter
2466 (W) A warning peculiar to VMS. A logical name was encountered when preparing
2467 to iterate over %ENV which violates the syntactic rules governing logical
2468 names. Because it cannot be translated normally, it is skipped, and will not
2469 appear in %ENV. This may be a benign occurrence, as some software packages
2470 might directly modify logical name tables and introduce nonstandard names,
2471 or it may indicate that a logical name table has been corrupted.
2473 =item Probable precedence problem on %s
2475 (W) The compiler found a bareword where it expected a conditional,
2476 which often indicates that an || or && was parsed as part of the
2477 last argument of the previous construct, for example:
2481 =item regexp too big
2483 (F) The current implementation of regular expressions uses shorts as
2484 address offsets within a string. Unfortunately this means that if
2485 the regular expression compiles to longer than 32767, it'll blow up.
2486 Usually when you want a regular expression this big, there is a better
2487 way to do it with multiple statements. See L<perlre>.
2489 =item Use of "$$<digit>" to mean "${$}<digit>" is deprecated
2491 (D) Perl versions before 5.004 misinterpreted any type marker followed
2492 by "$" and a digit. For example, "$$0" was incorrectly taken to mean
2493 "${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004.
2495 However, the developers of Perl 5.004 could not fix this bug completely,
2496 because at least two widely-used modules depend on the old meaning of
2497 "$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the
2498 old (broken) way inside strings; but it generates this message as a
2499 warning. And in Perl 5.005, this special treatment will cease.
2505 If you find what you think is a bug, you might check the
2506 articles recently posted to the comp.lang.perl.misc newsgroup.
2507 There may also be information at http://www.perl.com/perl/, the Perl
2510 If you believe you have an unreported bug, please run the B<perlbug>
2511 program included with your release. Make sure to trim your bug down
2512 to a tiny but sufficient test case. Your bug report, along with the
2513 output of C<perl -V>, will be sent off to perlbug@perl.com to be
2514 analysed by the Perl porting team.
2518 The F<Changes> file for exhaustive details on what changed.
2520 The F<INSTALL> file for how to build Perl.
2522 The F<README> file for general stuff.
2524 The F<Artistic> and F<Copying> files for copyright information.
2528 Written by Gurusamy Sarathy <F<gsar@activestate.com>>, with many
2529 contributions from The Perl Porters.
2531 Send omissions or corrections to <F<perlbug@perl.com>>.