3 perldelta - what's new for perl v5.6.0
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 5.6.0, 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 v5.6.0 will be numbered v5.7.x,
69 beginning with v5.7.0, and the next major production release following
70 v5.6.0 will be v5.8.0.
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 v5.6.0 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 should be read as being
86 equivalent to a floating point value of 5.006_001 in the older format,
89 =item Literals of the form C<1.2.3> parse differently
91 Previously, numeric literals with more than one dot in them were
92 interpreted as a floating point number concatenated with one or more
93 numbers. Such "numbers" are now parsed as strings composed of the
96 For example, C<print 97.98.99> used to output C<97.9899> in earlier
97 versions, but now prints C<abc>.
99 See L<Support for strings represented as a vector of ordinals> below.
101 =item Possibly changed pseudo-random number generator
103 In 5.005_0x and earlier, perl's rand() function used the C library
104 rand(3) function. As of 5.005_52, Configure tests for drand48(),
105 random(), and rand() (in that order) and picks the first one it finds.
106 Perl programs that depend on reproducing a specific set of pseudo-random
107 numbers will now likely produce different output. You can use
108 C<sh Configure -Drandfunc=rand> to obtain the old behavior.
110 =item Hashing function for hash keys has changed
112 Perl hashes are not order preserving. The apparently random order
113 encountered when iterating on the contents of a hash is determined
114 by the hashing algorithm used. To improve the distribution of lower
115 bits in the hashed value, the algorithm has changed slightly as of
116 5.005_52. When iterating over hashes, this may yield a random order
117 that is B<different> from that of previous versions.
119 =item C<undef> fails on read only values
121 Using the C<undef> operator on a readonly value (such as $1) has
122 the same effect as assigning C<undef> to the readonly value--it
125 =item Close-on-exec bit may be set on pipe and socket handles
127 On systems that support a close-on-exec flag on filehandles, the
128 flag will be set for any handles created by pipe(), socketpair(),
129 socket(), and accept(), if that is warranted by the value of $^F
130 that may be in effect. Earlier versions neglected to set the flag
131 for handles created with these operators. See L<perlfunc/pipe>,
132 L<perlfunc/socketpair>, L<perlfunc/socket>, L<perlfunc/accept>,
135 =item Writing C<"$$1"> to mean C<"${$}1"> is unsupported
137 Perl 5.004 deprecated the interpretation of C<$$1> and
138 similar within interpolated strings to mean C<$$ . "1">,
139 but still allowed it.
141 In Perl 5.6 and later, C<"$$1"> always means C<"${$1}">.
143 =item delete(), values() and C<\(%h)> operate on aliases to values, not copies
145 delete(), each(), values() and hashes in a list context return the actual
146 values in the hash, instead of copies (as they used to in earlier
147 versions). Typical idioms for using these constructs copy the
148 returned values, but this can make a significant difference when
149 creating references to the returned values.
151 Keys in the hash are still returned as copies when iterating on
154 =item vec(EXPR,OFFSET,BITS) enforces powers-of-two BITS
156 vec() generates a run-time error if the BITS argument is not
157 a valid power-of-two integer.
159 =item Text of some diagnostic output has changed
161 Most references to internal Perl operations in diagnostics
162 have been changed to be more descriptive. This may be an
163 issue for programs that may incorrectly rely on the exact
164 text of diagnostics for proper functioning.
166 =item C<%@> has been removed
168 The undocumented special variable C<%@> that used to accumulate
169 "background" errors (such as those that happen in DESTROY())
170 has been removed, because it could potentially result in memory
173 =item Parenthesized not() behaves like a list operator
175 The C<not> operator now falls under the "if it looks like a function,
176 it behaves like a function" rule.
178 As a result, the parenthesized form can be used with C<grep> and C<map>.
179 The following construct used to be a syntax error before, but it works
182 grep not($_), @things;
184 On the other hand, using C<not> with a literal list slice may not
185 work. The following previously allowed construct:
187 print not (1,2,3)[0];
189 needs to be written with additional parentheses now:
191 print not((1,2,3)[0]);
193 The behavior remains unaffected when C<not> is not followed by parentheses.
195 =item Semantics of bareword prototype C<(*)> have changed
197 Arguments prototyped as C<*> will now be visible within the subroutine
198 as either a simple scalar or as a reference to a typeglob. Perl 5.005
199 always coerced simple scalar arguments to a typeglob, which wasn't useful
200 in situations where the subroutine must distinguish between a simple
201 scalar and a typeglob. See L<perlsub/Prototypes>.
203 =head2 On 64-bit platforms the semantics of bit operators have changed
205 If your platform is either natively 64-bit or your Perl has been
206 configured to used 64-bit integers (say C<perl -V> and see what is
207 your ivsize: if it is 8, you are 64-bit) , be warned that the
208 semantics of all the bitwise numeric operators (& | ^ ~ << >>) have
209 been changed. They used to be forced to be 32 bits wide, but now in
210 the aforementioned platforms they are 64 bits wide. Most dramatically
211 this affects the unary ~: what used to be 32 bits wide, is now 64 bits
212 wide. If you depend on your integers being 32 bits wide, mask off the
213 excess bits with C<& 0xffffffff>.
217 =head2 C Source Incompatibilities
221 =item C<PERL_POLLUTE>
223 Release 5.005 grandfathered old global symbol names by providing preprocessor
224 macros for extension source compatibility. As of release 5.6, these
225 preprocessor definitions are not available by default. You need to explicitly
226 compile perl with C<-DPERL_POLLUTE> to get these definitions. For
227 extensions still using the old symbols, this option can be
228 specified via MakeMaker:
230 perl Makefile.PL POLLUTE=1
232 =item C<PERL_IMPLICIT_CONTEXT>
234 PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
235 with one of -Dusethreads, -Dusemultiplicity, or both. It is not
236 intended to be enabled by users at this time.
238 This new build option provides a set of macros for all API functions
239 such that an implicit interpreter/thread context argument is passed to
240 every API function. As a result of this, something like C<sv_setsv(foo,bar)>
241 amounts to a macro invocation that actually translates to something like
242 C<Perl_sv_setsv(my_perl,foo,bar)>. While this is generally expected
243 to not have any significant source compatibility issues, the difference
244 between a macro and a real function call will need to be considered.
246 This means that there B<is> a source compatibility issue as a result of
247 this if your extensions attempt to use pointers to any of the Perl API
250 Note that the above issue is not relevant to the default build of
251 Perl, whose interfaces continue to match those of prior versions
252 (but subject to the other options described here).
254 See L<perlguts/"The Perl API"> for detailed information on the
255 ramifications of building Perl using this option.
257 =item C<PERL_POLLUTE_MALLOC>
259 Enabling Perl's malloc in release 5.005 and earlier caused
260 the namespace of system versions of the malloc family of functions to
261 be usurped by the Perl versions, since by default they used the
264 Besides causing problems on platforms that do not allow these functions to
265 be cleanly replaced, this also meant that the system versions could not
266 be called in programs that used Perl's malloc. Previous versions of Perl
267 have allowed this behaviour to be suppressed with the HIDEMYMALLOC and
268 EMBEDMYMALLOC preprocessor definitions.
270 As of release 5.6, Perl's malloc family of functions have default names
271 distinct from the system versions. You need to explicitly compile perl with
272 C<-DPERL_POLLUTE_MALLOC> to get the older behaviour. HIDEMYMALLOC
273 and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now
276 Note that these functions do B<not> constitute Perl's memory allocation API.
277 See L<perlguts/"Memory Allocation"> for further information about that.
281 =head2 Compatible C Source API Changes
285 =item C<PATCHLEVEL> is now C<PERL_VERSION>
287 The cpp macros C<PERL_REVISION>, C<PERL_VERSION>, and C<PERL_SUBVERSION>
288 are now available by default from perl.h, and reflect the base revision,
289 patchlevel, and subversion respectively. C<PERL_REVISION> had no
290 prior equivalent, while C<PERL_VERSION> and C<PERL_SUBVERSION> were
291 previously available as C<PATCHLEVEL> and C<SUBVERSION>.
293 The new names cause less pollution of the B<cpp> namespace and reflect what
294 the numbers have come to stand for in common practice. For compatibility,
295 the old names are still supported when F<patchlevel.h> is explicitly
296 included (as required before), so there is no source incompatibility
299 =item Support for C++ exceptions
301 change#3386, also needs perlguts documentation
302 [TODO - Chip Salzenberg <chip@perlsupport.com>]
306 =head2 Binary Incompatibilities
308 In general, the default build of this release is expected to be binary
309 compatible for extensions built with the 5.005 release or its maintenance
310 versions. However, specific platforms may have broken binary compatibility
311 due to changes in the defaults used in hints files. Therefore, please be
312 sure to always check the platform-specific README files for any notes to
315 The usethreads or usemultiplicity builds are B<not> binary compatible
316 with the corresponding builds in 5.005.
318 On platforms that require an explicit list of exports (AIX, OS/2 and Windows,
319 among others), purely internal symbols such as parser functions and the
320 run time opcodes are not exported by default. Perl 5.005 used to export
321 all functions irrespective of whether they were considered part of the
324 For the full list of public API functions, see L<perlapi>.
326 =head1 Installation and Configuration Improvements
328 =head2 -Dusethreads means something different
330 WARNING: Support for threads continues to be an experimental feature.
331 Interfaces and implementation are subject to sudden and drastic changes.
333 The -Dusethreads flag now enables the experimental interpreter-based thread
334 support by default. To get the flavor of experimental threads that was in
335 5.005 instead, you need to run Configure with "-Dusethreads -Duse5005threads".
337 As of v5.5.640, interpreter-threads support is still lacking a way to
338 create new threads from Perl (i.e., C<use Thread;> will not work with
339 interpreter threads). C<use Thread;> continues to be available when you
340 ask for use5005threads, bugs and all.
342 =head2 New Configure flags
344 The following new flags may be enabled on the Configure command line
345 by running Configure with C<-Dflag>.
348 usethreads useithreads (new interpreter threads: no Perl API yet)
349 usethreads use5005threads (threads as they were in 5.005)
351 use64bitint (equal to now deprecated 'use64bits')
357 usesocks (only SOCKS v5 supported)
359 =head2 Threadedness and 64-bitness now more daring
361 The Configure options enabling the use of threads and the use of
362 64-bitness are now more daring in the sense that they no more have an
363 explicit list of operating systems of known threads/64-bit
364 capabilities. In other words: if your operating system has the
365 necessary APIs and datatypes, you should be able just to go ahead and
366 use them, for threads by Configure -Dusethreads, and for 64 bits
367 either explicitly by Configure -Duse64bitint or implicitly if your
368 system has 64 bit wide datatypes. See also L<"64-bit support">.
372 Some platforms have "long doubles", floating point numbers of even
373 larger range than ordinary "doubles". To enable using long doubles for
374 Perl's scalars, use -Duselongdouble.
378 You can enable both -Duse64bitint and -Dlongdouble by -Dusemorebits.
379 See also L<"64-bit support">.
381 =head2 -Duselargefiles
383 Some platforms support large files, files larger than two gigabytes.
384 See L<"Large file support"> for more information.
386 =head2 installusrbinperl
388 You can use "Configure -Uinstallusrbinperl" which causes installperl
389 to skip installing perl also as /usr/bin/perl. This is useful if you
390 prefer not to modify /usr/bin for some reason or another but harmful
391 because many scripts assume to find Perl in /usr/bin/perl.
395 You can use "Configure -Dusesocks" which causes Perl to probe
396 for the SOCKS (v5, not v4) proxy protocol library,
397 http://www.socks.nec.com/
401 You can "post-edit" the Configure variables using the Configure C<-A>
402 flag. The editing happens immediately after the platform specific
403 hints files have been processed but before the actual configuration
404 process starts. Run C<Configure -h> to find out the full C<-A> syntax.
406 =head2 Enhanced Installation Directories
408 The installation structure has been enriched to improve the support
409 for maintaining multiple versions of perl, to provide locations for
410 vendor-supplied modules, scripts, and manpages, and to ease maintenance
411 of locally-added modules, scripts, and manpages. See the section on
412 Installation Directories in the INSTALL file for complete details.
413 For most users building and installing from source, the defaults should
416 If you previously used C<Configure -Dsitelib> or C<-Dsitearch> to set
417 special values for library directories, you might wish to consider using
418 the new C<-Dsiteprefix> setting instead. Also, if you wish to re-use a
419 config.sh file from an earlier version of perl, you should be sure to
420 check that Configure makes sensible choices for the new directories.
421 See INSTALL for complete details.
425 =head2 Unicode and UTF-8 support
427 Perl can optionally use UTF-8 as its internal representation for character
428 strings. The C<utf8> and C<bytes> pragmas are used to control this support
429 in the current lexical scope. See L<perlunicode>, L<utf8> and L<bytes> for
432 =head2 Interpreter cloning, threads, and concurrency
434 WARNING: This is an experimental feature in a pre-alpha state. Use
437 Perl 5.005_63 introduces the beginnings of support for running multiple
438 interpreters concurrently in different threads. In conjunction with
439 the perl_clone() API call, which can be used to selectively duplicate
440 the state of any given interpreter, it is possible to compile a
441 piece of code once in an interpreter, clone that interpreter
442 one or more times, and run all the resulting interpreters in distinct
445 On Windows, this feature is used to emulate fork() at the interpreter
446 level. See L<perlfork>.
448 This feature is still in evolution. It is eventually meant to be used
449 to selectively clone a subroutine and data reachable from that
450 subroutine in a separate interpreter and run the cloned subroutine
451 in a separate thread. Since there is no shared data between the
452 interpreters, little or no locking will be needed (unless parts of
453 the symbol table are explicitly shared). This is obviously intended
454 to be an easy-to-use replacement for the existing threads support.
456 Support for cloning interpreters and interpreter concurrency can be
457 enabled using the -Dusethreads Configure option (see win32/Makefile for
458 how to enable it on Windows.) The resulting perl executable will be
459 functionally identical to one that was built with -Dmultiplicity, but
460 the perl_clone() API call will only be available in the former.
462 -Dusethreads enables, the cpp macros USE_ITHREADS by default, which enables
463 Perl source code changes that provide a clear separation between the op tree
464 and the data it operates with. The former is considered immutable, and can
465 therefore be shared between an interpreter and all of its clones, while the
466 latter is considered local to each interpreter, and is therefore copied for
469 Note that building Perl with the -Dusemultiplicity Configure option
470 is adequate if you wish to run multiple B<independent> interpreters
471 concurrently in different threads. -Dusethreads only provides the
472 additional functionality of the perl_clone() API call and other
473 support for running B<cloned> interpreters concurrently.
475 [XXX TODO - the Compiler backends may be broken when USE_ITHREADS is
478 =head2 Lexically scoped warning categories
480 You can now control the granularity of warnings emitted by perl at a finer
481 level using the C<use warnings> pragma. See L<warnings> and L<perllexwarn>
484 =head2 Lvalue subroutines
486 WARNING: This is an experimental feature.
489 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>,
490 Tuomas Lukka <lukka@iki.fi>)]
492 =head2 "our" declarations
494 An "our" declaration introduces a value that can be best understood
495 as a lexically scoped symbolic alias to a global variable in the
496 package that was current where the variable was declared. This is
497 mostly useful as an alternative to the C<vars> pragma, but also provides
498 the opportunity to introduce typing and other attributes for such
499 variables. See L<perlfunc/our>.
501 =head2 Support for strings represented as a vector of ordinals
503 Literals of the form C<v1.2.3.4> are now parsed as a string composed of
504 of characters with the specified ordinals. This is an alternative, more
505 readable way to construct (possibly unicode) strings instead of
506 interpolating characters, as in C<"\x{1}\x{2}\x{3}\x{4}">. The leading
507 C<v> may be omitted if there are more than two ordinals, so C<1.2.3> is
508 parsed the same as C<v1.2.3>.
510 Strings written in this form are also useful to represent version "numbers".
511 It is easy to compare such version "numbers" (which are really just plain
512 strings) using any of the usual string comparison operators C<eq>, C<ne>,
513 C<lt>, C<gt>, etc., or perform bitwise string operations on them using C<|>,
516 In conjunction with the new C<$^V> magic variable (which contains
517 the perl version as a string), such literals can be used as a readable way
518 to check if you're running a particular version of Perl:
520 # this will parse in older versions of Perl also
521 if ($^V and $^V gt v5.5.640) {
522 # new features supported
525 C<require> and C<use> also have some special magic to support such literals.
526 They will be interpreted as a version rather than as a module name:
528 require v5.6.0; # croak if $^V lt v5.6.0
529 use v5.6.0; # same, but croaks at compile-time
531 Alternatively, the C<v> may be omitted if there is more than one dot:
536 Also, C<sprintf> and C<printf> support the Perl-specific format flag C<%v>
537 to print ordinals of characters in arbitrary strings:
539 printf "v%vd", $^V; # prints current version, such as "v5.5.650"
540 printf "%*vX", ":", $addr; # formats IPv6 address
541 printf "%*vb", " ", $bits; # displays bitstring
543 See L<perldata/"Scalar value constructors"> for additional information.
545 =head2 Weak references
547 WARNING: This is an experimental feature.
549 In previous versions of Perl, you couldn't cache objects so as
550 to allow them to be deleted if the last reference from outside
551 the cache is deleted. The reference in the cache would hold a
552 reference count on the object and the objects would never be
555 Another familiar problem is with circular references. When an
556 object references itself, its reference count would never go
557 down to zero, and it would not get destroyed until the program
560 Weak references solve this by allowing you to "weaken" any
561 reference, that is, make it not count towards the reference count.
562 When the last non-weak reference to an object is deleted, the object
563 is destroyed and all the weak references to the object are
564 automatically undef-ed.
566 To use this feature, you need the WeakRef package from CPAN, which
567 contains additional documentation.
569 change#3385, also need perlguts documentation
570 [TODO - Tuomas Lukka <lukka@iki.fi>]
572 =head2 File globbing implemented internally
574 WARNING: This is currently an experimental feature. Interfaces and
575 implementation are likely to change.
577 Perl now uses the File::Glob implementation of the glob() operator
578 automatically. This avoids using an external csh process and the
579 problems associated with it.
581 =head2 Binary numbers supported
583 Binary numbers are now supported as literals, in s?printf formats, and
587 printf "The answer is: %b\n", oct("0b101010");
589 =head2 Some arrows may be omitted in calls through references
591 Perl now allows the arrow to be omitted in many constructs
592 involving subroutine calls through references. For example,
593 C<< $foo[10]->('foo') >> may now be written C<$foo[10]('foo')>.
594 This is rather similar to how the arrow may be omitted from
595 C<< $foo[10]->{'foo'} >>. Note however, that the arrow is still
596 required for C<< foo(10)->('bar') >>.
598 =head2 exists() is supported on subroutine names
600 The exists() builtin now works on subroutine names. A subroutine
601 is considered to exist if it has been declared (even if implicitly).
602 See L<perlfunc/exists> for examples.
604 =head2 exists() and delete() are supported on array elements
606 The exists() and delete() builtins now work on simple arrays as well.
607 The behavior is similar to that on hash elements.
609 exists() can be used to check whether an array element has been
610 initialized. This avoids autovivifying array elements that don't exist.
611 If the array is tied, the EXISTS() method in the corresponding tied
612 package will be invoked.
614 delete() may be used to remove an element from the array and return
615 it. The array element at that position returns to its unintialized
616 state, so that testing for the same element with exists() will return
617 false. If the element happens to be the one at the end, the size of
618 the array also shrinks up to the highest element that tests true for
619 exists(), or 0 if none such is found. If the array is tied, the DELETE()
620 method in the corresponding tied package will be invoked.
622 See L<perlfunc/exists> and L<perlfunc/delete> for examples.
624 =head2 syswrite() ease-of-use
626 The length argument of C<syswrite()> has become optional.
628 =head2 File and directory handles can be autovivified
630 Similar to how constructs such as C<< $x->[0] >> autovivify a reference,
631 handle constructors (open(), opendir(), pipe(), socketpair(), sysopen(),
632 socket(), and accept()) now autovivify a file or directory handle
633 if the handle passed to them is an uninitialized scalar variable. This
634 allows the constructs such as C<open(my $fh, ...)> and C<open(local $fh,...)>
635 to be used to create filehandles that will conveniently be closed
636 automatically when the scope ends, provided there are no other references
637 to them. This largely eliminates the need for typeglobs when opening
638 filehandles that must be passed around, as in the following example:
642 or die "Can't open '@_': $!";
647 my $f = myopen("</etc/motd");
649 # $f implicitly closed here
652 [TODO - this idiom needs more pod penetration]
654 =head2 64-bit support
656 NOTE: The Configure flags -Duselonglong and -Duse64bits
657 have been deprecated. Use -Duse64bitint instead.
659 Any platform that has 64-bit integers either (a) natively as longs or
660 ints (b) via special compiler flags (c) using long long are able to
661 use "quads" (64-integers) as follows:
667 constants (decimal, hexadecimal, octal, binary) in the code
671 arguments to oct() and hex()
675 arguments to print(), printf() and sprintf() (flag prefixes ll, L, q)
683 pack() and unpack() "q" and "Q" formats
687 in basic arithmetics: + - * / % (NOTE: operating close to the limits
688 of the integer values may produce surprising results)
692 in bit arithmetics: & | ^ ~ << >> (NOTE: these used to be forced
701 Note that unless you have the case (a) you will have to configure
702 and compile Perl using the -Duse64bitint Configure flag.
704 There are actually two modes of 64-bitness: the first one is achieved
705 using Configure -Duse64bitint and the second one using Configure
706 -Duse64bitall. The difference is that the first one is minimal and
707 the second one maximal. The first one does only as much as is
708 required to get 64-bit integers into Perl (this may mean, for example,
709 using "long longs") while your memory may still be limited to 2
710 gigabytes (because your pointers most likely are 32-bit); the second
711 one goes all the way by attempting to switch also longs (and pointers)
712 being 64-bit. This may create an even more binary incompatible Perl
713 than -Duse64bitint: the resulting executable may not run at all in a
714 CPU-bit box, or you may have to reboot/reconfigure/rebuild your
715 operating system to be 64-bit aware.
717 Natively 64-bit systems like Alpha and Cray need neither -Duse64bitint
720 Last but not least: note that due to Perl's habit of always using
721 floating point numbers the quads are still not true integers.
722 When quads overflow their limits (0...18_446_744_073_709_551_615 unsigned,
723 -9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they
724 are silently promoted to floating point numbers, after which they will
725 start losing precision (their lower digits).
727 =head2 Large file support
729 If you have filesystems that support "large files" (files larger than
730 2 gigabytes), you may now also be able to create and access them from
731 Perl. You have to use Configure -Duselargefiles. Turning on the
732 large file support turns on also the 64-bit support on many platforms.
733 Beware that unless your filesystem also supports "sparse files" seeking
734 to umpteen petabytes may be unadvisable.
736 Note that in addition to requiring a proper file system to do large
737 files you may also need to adjust your per-process (or your
738 per-system, or per-process-group, or per-user-group) maximum filesize
739 limits before running Perl scripts that try to handle large files,
740 especially if you intend to write such files.
742 Finally, in addition to your process/process group maximum filesize
743 limits, you may have quota limits on your filesystems that stop you
744 (your user id or your user group id) from using large files.
746 Adjusting your process/user/group/file system/operating system limits
747 is outside the scope of Perl core language. For process limits, you
748 may try increasing the limits using your shell's limits/limit/ulimit
749 command before running Perl. The BSD::Resource extension (not
750 included with the standard Perl distribution) may also be of use, it
751 offers the getrlimit/setrlimit interface that can be used to adjust
752 process resource usage limits, including the maximum filesize limit.
756 In some systems you may be able to use long doubles to enhance the
757 range and precision of your double precision floating point numbers
758 (that is, Perl's numbers). Use Configure -Duselongdouble to enable
759 this support (if it is available).
763 You can "Configure -Dusemorebits" to turn on both the 64-bit support
764 and the long double support.
766 =head2 Enhanced support for sort() subroutines
768 Perl subroutines with a prototype of C<($$)> and XSUBs in general can
769 now be used as sort subroutines. In either case, the two elements to
770 be compared are passed as normal parameters in @_. See L<perlfunc/sort>.
772 For unprototyped sort subroutines, the historical behavior of passing
773 the elements to be compared as the global variables $a and $b remains
776 =head2 Better syntax checks on parenthesized unary operators
780 print defined(&foo,&bar,&baz);
781 print uc("foo","bar","baz");
784 used to be accidentally allowed in earlier versions, and produced
785 unpredictable behaviour. Some produced ancillary warnings
786 when used in this way; others silently did the wrong thing.
788 The parenthesized forms of most unary operators that expect a single
789 argument now ensure that they are not called with more than one
790 argument, making the cases shown above syntax errors. The usual
793 print defined &foo, &bar, &baz;
794 print uc "foo", "bar", "baz";
797 remains unchanged. See L<perlop>.
799 =head2 POSIX character class syntax [: :] supported
801 For example to match alphabetic characters use /[[:alpha:]]/.
802 See L<perlre> for details.
804 =head2 Improved C<qw//> operator
806 The C<qw//> operator is now evaluated at compile time into a true list
807 instead of being replaced with a run time call to C<split()>. This
808 removes the confusing misbehaviour of C<qw//> in scalar context, which
809 had inherited that behaviour from split().
813 $foo = ($bar) = qw(a b c); print "$foo|$bar\n";
815 now correctly prints "3|a", instead of "2|a".
817 =head2 pack() format 'Z' supported
819 The new format type 'Z' is useful for packing and unpacking null-terminated
820 strings. See L<perlfunc/"pack">.
822 =head2 pack() format modifier '!' supported
824 The new format type modifier '!' is useful for packing and unpacking
825 native shorts, ints, and longs. See L<perlfunc/"pack">.
827 =head2 pack() and unpack() support counted strings
829 The template character '/' can be used to specify a counted string
830 type to be packed or unpacked. See L<perlfunc/"pack">.
832 =head2 Comments in pack() templates
834 The '#' character in a template introduces a comment up to
835 end of the line. This facilitates documentation of pack()
838 =head2 $^X variables may now have names longer than one character
840 Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax
841 error. Now variable names that begin with a control character may be
842 arbitrarily long. However, for compatibility reasons, these variables
843 I<must> be written with explicit braces, as C<${^XY}> for example.
844 C<${^XYZ}> is synonymous with ${"\cXYZ"}. Variable names with more
845 than one control character, such as C<${^XY^Z}>, are illegal.
847 The old syntax has not changed. As before, `^X' may be either a
848 literal control-X character or the two-character sequence `caret' plus
849 `X'. When braces are omitted, the variable name stops after the
850 control character. Thus C<"$^XYZ"> continues to be synonymous with
851 C<$^X . "YZ"> as before.
853 As before, lexical variables may not have names beginning with control
854 characters. As before, variables whose names begin with a control
855 character are always forced to be in package `main'. All such variables
856 are reserved for future extensions, except those that begin with
857 C<^_>, which may be used by user programs and are guaranteed not to
858 acquire special meaning in any future version of Perl.
860 =head2 C<use attrs> implicit in subroutine attributes
862 Formerly, if you wanted to mark a subroutine as being a method call or
863 as requiring an automatic lock() when it is entered, you had to declare
864 that with a C<use attrs> pragma in the body of the subroutine.
865 That can now be accomplished with declaration syntax, like this:
867 sub mymethod : locked method ;
869 sub mymethod : locked method {
873 sub othermethod :locked :method ;
875 sub othermethod :locked :method {
880 (Note how only the first C<:> is mandatory, and whitespace surrounding
881 the C<:> is optional.)
883 F<AutoSplit.pm> and F<SelfLoader.pm> have been updated to keep the attributes
884 with the stubs they provide. See L<attributes>.
886 =head2 Regular expression improvements
888 change#2827,2373,2372,2365,1813,1800,4112,4158,4215,4301
889 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
891 =head2 Overloading improvements
894 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
896 =head2 open() with more than two arguments
898 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
900 =head2 Support for interpolating named characters
903 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
905 =head2 Experimental support for user-hooks in @INC
907 [TODO - Ken Fox <kfox@ford.com>]
909 =head2 C<require> and C<do> may be overridden
911 C<require> and C<do 'file'> operations may be overridden locally
912 by importing subroutines of the same name into the current package
913 (or globally by importing them into the CORE::GLOBAL:: namespace).
914 Overriding C<require> will also affect C<use>, provided the override
915 is visible at compile-time.
916 See L<perlsub/"Overriding Built-in Functions">.
918 =head2 New variable $^C reflects C<-c> switch
920 C<$^C> has a boolean value that reflects whether perl is being run
921 in compile-only mode (i.e. via the C<-c> switch). Since
922 BEGIN blocks are executed under such conditions, this variable
923 enables perl code to determine whether actions that make sense
924 only during normal running are warranted. See L<perlvar>.
926 =head2 New variable $^V contains Perl version as a string
928 C<$^V> contains the Perl version number as a string composed of
929 characters whose ordinals match the version numbers, e.g., v5.6.0.
930 This may be used in string comparisons.
932 See C<Support for strings represented as a vector of ordinals> for an
935 =head2 Optional Y2K warnings
937 If Perl is built with the cpp macro C<PERL_Y2KWARN> defined,
938 it emits optional warnings when concatenating the number 19
941 This behavior must be specifically enabled when running Configure.
942 See F<INSTALL> and F<README.Y2K>.
944 =head1 Significant bug fixes
946 =head2 <HANDLE> on empty files
948 With C<$/> set to C<undef>, "slurping" an empty file returns a string of
949 zero length (instead of C<undef>, as it used to) the first time the
950 HANDLE is read after C<$/> is set to C<undef>. Further reads yield
953 This means that the following will append "foo" to an empty file (it used
956 perl -0777 -pi -e 's/^/foo/' empty_file
960 perl -pi -e 's/^/foo/' empty_file
962 is unchanged (it continues to leave the file empty).
964 =head2 C<eval '...'> improvements
966 Line numbers (as reflected by caller() and most diagnostics) within
967 C<eval '...'> were often incorrect when here documents were involved.
968 This has been corrected.
970 Lexical lookups for variables appearing in C<eval '...'> within
971 functions that were themselves called within an C<eval '...'> were
972 searching the wrong place for lexicals. The lexical search now
973 correctly ends at the subroutine's block boundary.
975 Parsing of here documents used to be flawed when they appeared as
976 the replacement expression in C<eval 's/.../.../e'>. This has
979 =head2 All compilation errors are true errors
981 Some "errors" encountered at compile time were by neccessity
982 generated as warnings followed by eventual termination of the
983 program. This enabled more such errors to be reported in a
984 single run, rather than causing a hard stop at the first error
985 that was encountered.
987 The mechanism for reporting such errors has been reimplemented
988 to queue compile-time errors and report them at the end of the
989 compilation as true errors rather than as warnings. This fixes
990 cases where error messages leaked through in the form of warnings
991 when code was compiled at run time using C<eval STRING>, and
992 also allows such errors to be reliably trapped using __DIE__ hooks.
994 =head2 Automatic flushing of output buffers
996 fork(), exec(), system(), qx//, and pipe open()s now flush buffers
997 of all files opened for output when the operation
998 was attempted. This mostly eliminates confusing
999 buffering mishaps suffered by users unaware of how Perl internally
1002 =head2 Better diagnostics on meaningless filehandle operations
1004 Constructs such as C<< open(<FH>) >> and C<< close(<FH>) >>
1005 are compile time errors. Attempting to read from filehandles that
1006 were opened only for writing will now produce warnings (just as
1007 writing to read-only filehandles does).
1009 =head2 Where possible, buffered data discarded from duped input filehandle
1011 C<< open(NEW, "<&OLD") >> now attempts to discard any data that
1012 was previously read and buffered in C<OLD> before duping the handle.
1013 On platforms where doing this is allowed, the next read operation
1014 on C<NEW> will return the same data as the corresponding operation
1015 on C<OLD>. Formerly, it would have returned the data from the start
1016 of the following disk block instead.
1018 =head2 eof() has the same old magic as <>
1020 C<eof()> would return true if no attempt to read from C<< <> >> had
1021 yet been made. C<eof()> has been changed to have a little magic of its
1022 own, it now opens the C<< <> >> files.
1024 =head2 system(), backticks and pipe open now reflect exec() failure
1026 On Unix and similar platforms, system(), qx() and open(FOO, "cmd |")
1027 etc., are implemented via fork() and exec(). When the underlying
1028 exec() fails, earlier versions did not report the error properly,
1029 since the exec() happened to be in a different process.
1031 The child process now communicates with the parent about the
1032 error in launching the external command, which allows these
1033 constructs to return with their usual error value and set $!.
1035 =head2 Implicitly closed filehandles are safer
1037 Sometimes implicitly closed filehandles (as when they are localized,
1038 and Perl automatically closes them on exiting the scope) could
1039 inadvertently set $? or $!. This has been corrected.
1041 =head2 C<(\$)> prototype and C<$foo{a}>
1043 An scalar reference prototype now correctly allows a hash or
1044 array element in that slot.
1046 =head2 Pseudo-hashes work better
1048 Dereferencing some types of reference values in a pseudo-hash,
1049 such as C<< $ph->{foo}[1] >>, was accidentally disallowed. This has
1052 When applied to a pseudo-hash element, exists() now reports whether
1053 the specified value exists, not merely if the key is valid.
1055 delete() now works on pseudo-hashes. When given a pseudo-hash element
1056 or slice it deletes the values corresponding to the keys (but not the keys
1057 themselves). See L<perlref/"Pseudo-hashes: Using an array as a hash">.
1059 Pseudo-hash slices with constant keys are now optimized to array lookups
1062 The C<fields> pragma now provides ways to create pseudo-hashes, via
1063 fields::new() and fields::phash(). See L<fields>.
1065 =head2 C<goto &sub> and AUTOLOAD
1067 The C<goto &sub> construct works correctly when C<&sub> happens
1070 =head2 C<-bareword> allowed under C<use integer>
1072 The autoquoting of barewords preceded by C<-> did not work
1073 in prior versions when the C<integer> pragma was enabled.
1074 This has been fixed.
1076 =head2 Boolean assignment operators are legal lvalues
1078 Constructs such as C<($a ||= 2) += 1> are now allowed.
1080 =head2 C<sort $coderef @foo> allowed
1082 sort() did not accept a subroutine reference as the comparison
1083 function in earlier versions. This is now permitted.
1085 =head2 Failures in DESTROY()
1087 When code in a destructor threw an exception, it went unnoticed
1088 in earlier versions of Perl, unless someone happened to be
1089 looking in $@ just after the point the destructor happened to
1090 run. Such failures are now visible as warnings when warnings are
1093 =head2 Locale bugs fixed
1095 printf() and sprintf() previously reset the numeric locale
1096 back to the default "C" locale. This has been fixed.
1098 Numbers formatted according to the local numeric locale
1099 (such as using a decimal comma instead of a decimal dot) caused
1100 "isn't numeric" warnings, even while the operations accessing
1101 those numbers produced correct results. The warnings are gone.
1105 The C<eval 'return sub {...}'> construct could sometimes leak
1106 memory. This has been fixed.
1108 Operations that aren't filehandle constructors used to leak memory
1109 when used on invalid filehandles. This has been fixed.
1111 Constructs that modified C<@_> could fail to deallocate values
1112 in C<@_> and thus leak memory. This has been corrected.
1114 =head2 Spurious subroutine stubs after failed subroutine calls
1116 Perl could sometimes create empty subroutine stubs when a
1117 subroutine was not found in the package. Such cases stopped
1118 later method lookups from progressing into base packages.
1119 This has been corrected.
1121 =head2 Consistent numeric conversions
1124 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1126 =head2 Taint failures under C<-U>
1128 When running in unsafe mode, taint violations could sometimes
1129 cause silent failures. This has been fixed.
1131 =head2 END blocks and the C<-c> switch
1133 Prior versions used to run BEGIN B<and> END blocks when Perl was
1134 run in compile-only mode. Since this is typically not the expected
1135 behavior, END blocks are not executed anymore when the C<-c> switch
1138 See L<CHECK blocks> for how to run things when the compile phase ends.
1140 =head2 Potential to leak DATA filehandles
1142 Using the C<__DATA__> token creates an implicit filehandle to
1143 the file that contains the token. It is the program's
1144 responsibility to close it when it is done reading from it.
1146 This caveat is now better explained in the documentation.
1149 =head2 Diagnostics follow STDERR
1151 Diagnostic output now goes to whichever file the C<STDERR> handle
1152 is pointing at, instead of always going to the underlying C runtime
1153 library's C<stderr>.
1155 =head2 Other fixes for better diagnostics
1157 Line numbers are no longer suppressed (under most likely circumstances)
1158 during the global destruction phase.
1160 Diagnostics emitted from code running in threads other than the main
1161 thread are now accompanied by the thread ID.
1163 Embedded null characters in diagnostics now actually show up. They
1164 used to truncate the message in prior versions.
1166 $foo::a and $foo::b are now exempt from "possible typo" warnings only
1167 if sort() is encountered in package foo.
1169 Unrecognized alphabetic escapes encountered when parsing quote
1170 constructs now generate a warning, since they may take on new
1171 semantics in later versions of Perl.
1173 =head1 Performance enhancements
1175 =head2 Simple sort() using { $a <=> $b } and the like are optimized
1177 Many common sort() operations using a simple inlined block are now
1178 optimized for faster performance.
1180 =head2 Optimized assignments to lexical variables
1182 Certain operations in the RHS of assignment statements have been
1183 optimized to directly set the lexical variable on the LHS,
1184 eliminating redundant copying overheads.
1186 =head2 Method lookups optimized
1188 [TODO - Chip Salzenberg <chip@perlsupport.com>]
1190 =head2 Faster mechanism to invoke XSUBs
1193 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1195 =head2 Perl_malloc() improvements
1198 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1200 =head2 Faster subroutine calls
1202 Minor changes in how subroutine calls are handled internally
1203 provide marginal improvements in performance.
1205 =head1 Platform specific changes
1207 =head2 Supported platforms
1213 VM/ESA is now supported.
1217 Siemens BS2000 is now supported under the POSIX Shell.
1221 The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread
1226 GNU/Hurd is now supported.
1230 Rhapsody/Darwin is now supported.
1234 EPOC is is now supported (on Psion 5).
1244 Perl now works with djgpp 2.02 (and 2.03 alpha).
1248 Environment variable names are not converted to uppercase any more.
1252 Wrong exit code from backticks now fixed.
1256 This port is still using its own builtin globbing.
1262 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1264 =head2 OS/390 (OpenEdition MVS)
1266 Support for this EBCDIC platform has not been renewed in this release.
1267 There are difficulties in reconciling Perl's standardization on UTF-8
1268 as its internal representation for characters with the EBCDIC character
1269 set, because the two are incompatible.
1271 It is unclear whether future versions will renew support for this
1272 platform, but the possibility exists.
1276 Numerous revisions and extensions to configuration, build, testing, and
1277 installation process to accomodate core changes and VMS-specific options
1279 Expand %ENV-handling code to allow runtime mapping to logical names,
1280 CLI symbols, and CRTL environ array
1282 Extension of subprocess invocation code to accept filespecs as command "verbs"
1284 Add to Perl command line processing the ability to use default file types and
1285 to recognize Unix-style C<2E<gt>&1>.
1287 Expansion of File::Spec::VMS routines, and integration into ExtUtils::MM_VMS
1289 Extension of ExtUtils::MM_VMS to handle complex extensions more flexibly
1291 Barewords at start of Unix-syntax paths may be treated as text rather than
1292 only as logical names
1294 Optional secure translation of several logical names used internally by Perl
1296 Miscellaneous bugfixing and porting of new core code to VMS
1298 Thanks are gladly extended to the many people who have contributed VMS
1299 patches, testing, and ideas.
1303 Site library searches failed to look for ".../site/5.XXX/lib"
1304 if ".../site/5.XXXYY/lib" wasn't found. This has been corrected.
1306 When given a pathname that consists only of a drivename, such
1307 as C<A:>, opendir() and stat() now use the current working
1308 directory for the drive rather than the drive root.
1310 The builtin XSUB functions in the Win32:: namespace are
1311 documented. See L<Win32>.
1313 $^X now contains the full path name of the running executable.
1315 A Win32::GetLongPathName() function is provided to complement
1316 Win32::GetFullPathName() and Win32::GetShortPathName(). See L<Win32>.
1318 POSIX::uname() is supported.
1320 system(1,...) now returns true process IDs rather than process
1321 handles. kill() accepts any real process id, rather than strictly
1322 return values from system(1,...).
1324 For better compatibility with Unix, C<kill(0, $pid)> can now be used to
1325 test whether a process exists.
1327 The C<Shell> module is supported.
1329 Rudimentary support for building under command.com in Windows 95
1332 Scripts are read in binary mode by default to allow ByteLoader (and
1333 the filter mechanism in general) to work properly. For compatibility,
1334 the DATA filehandle will be set to text mode if a carriage return is
1335 detected at the end of the line containing the __END__ or __DATA__
1336 token; if not, the DATA filehandle will be left open in binary mode.
1337 Earlier versions always opened the DATA filehandle in text mode.
1339 The glob() operator is implemented via the C<File::Glob> extension,
1340 which supports glob syntax of the C shell. This increases the flexibility
1341 of the glob() operator, but there may be compatibility issues for
1342 programs that relied on the older globbing syntax. If you want to
1343 preserve compatibility with the older syntax, you might want to put
1344 a C<use File::DosGlob;> in your program. For details and compatibility
1345 information, see L<File::Glob>.
1355 Compatibility tests for C<sub : attrs> vs the older C<use attrs>.
1359 Tests for new environment scalar capability (e.g., C<use Env qw($BAR);>).
1363 Tests for new environment array capability (e.g., C<use Env qw(@PATH);>).
1367 IO constants (SEEK_*, _IO*).
1371 Directory-related IO methods (new, read, close, rewind, tied delete).
1373 =item lib/io_multihomed
1375 INET sockets with multi-homed hosts.
1387 Regression tests for C<my ($x,@y,%z) : attrs> and <sub : attrs>.
1391 File test operators.
1395 Verify operations that access pad objects (lexicals and temporaries).
1399 Verify C<exists &sub> operations.
1403 =head1 Modules and Pragmata
1411 While used internally by Perl as a pragma, this module also
1412 provides a way to fetch subroutine and variable attributes.
1417 The Perl Compiler suite has been extensively reworked for this
1420 [TODO - Vishal Bhatia <vishal@gol.com>,
1421 Nick Ing-Simmons <nick@ni-s.u-net.com>]
1425 The ByteLoader is a dedicated extension to generate and run
1426 Perl bytecode. See L<ByteLoader>.
1430 References can now be used.
1432 The new version also allows a leading underscore in constant names, but
1433 disallows a double leading underscore (as in "__LINE__"). Some other names
1434 are disallowed or warned against, including BEGIN, END, etc. Some names
1435 which were forced into main:: used to fail silently in some cases; now they're
1436 fatal (outside of main::) and an optional warning (inside of main::).
1437 The ability to detect whether a constant had been set with a given name has
1445 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1449 A C<Maxdepth> setting can be specified to avoid venturing
1450 too deeply into deep data structures. See L<Data::Dumper>.
1452 Dumping C<qr//> objects works correctly.
1456 C<DB> is an experimental module that exposes a clean abstraction
1457 to Perl's debugging API.
1461 DB_File can now be built with Berkeley DB versions 1, 2 or 3.
1462 See C<ext/DB_File/Changes>.
1466 Devel::DProf, a Perl source code profiler has been added. See
1467 L<Devel::DProf> and L<dprofpp>.
1471 The Dumpvalue module provides screen dumps of Perl data.
1475 Overall, Benchmark results exhibit lower average error and better timing
1478 You can now run tests for I<n> seconds instead of guessing the right
1479 number of tests to run: e.g. timethese(-5, ...) will run each
1480 code for at least 5 CPU seconds. Zero as the "number of repetitions"
1481 means "for at least 3 CPU seconds". The output format has also
1482 changed. For example:
1484 use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
1486 will now output something like this:
1488 Benchmark: running a, b, each for at least 5 CPU seconds...
1489 a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
1490 b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
1492 New features: "each for at least N CPU seconds...", "wallclock secs",
1493 and the "@ operations/CPU second (n=operations)".
1495 timethese() now returns a reference to a hash of Benchmark objects containing
1496 the test results, keyed on the names of the tests.
1498 timethis() now returns the iterations field in the Benchmark result object
1501 timethese(), timethis(), and the new cmpthese() (see below) can also take
1502 a format specifier of 'none' to suppress output.
1504 A new function countit() is just like timeit() except that it takes a
1505 TIME instead of a COUNT.
1507 A new function cmpthese() prints a chart comparing the results of each test
1508 returned from a timethese() call. For each possible pair of tests, the
1509 percentage speed difference (iters/sec or seconds/iter) is shown.
1511 For other details, see L<Benchmark>.
1515 The Devel::Peek module provides access to the internal representation
1516 of Perl variables and data. It is a data debugging tool for the XS programmer.
1520 $PERL_VERSION now stands for C<$^V> (a string value) rather than for C<$]>
1525 Env now supports accessing environment variables like PATH as array
1528 =item ExtUtils::MakeMaker
1530 change#4135, also needs docs in module pod
1531 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1535 More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for
1536 large file (more than 4GB) access Note that the O_LARGEFILE is
1537 automatically/transparently added to sysopen() flags if large file
1538 support has been configured), Free/Net/OpenBSD locking behaviour flags
1539 F_FLOCK, F_POSIX, Linux F_SHLCK, and O_ACCMODE: the combined mask of
1540 O_RDONLY, O_WRONLY, and O_RDWR. The seek()/sysseek() constants
1541 SEEK_SET, SEEK_CUR, and SEEK_END are available via the C<:seek> tag.
1542 The chmod()/stat() S_IF* constants and S_IS* functions are available
1543 via the C<:mode> tag.
1548 A compare_text() function has been added, which allows custom
1549 comparison functions. See L<File::Compare>.
1553 File::Find now works correctly when the wanted() function is either
1554 autoloaded or is a symbolic reference.
1556 A bug that caused File::Find to lose track of the working directory
1557 when pruning top-level directories has been fixed.
1559 File::Find now also supports several other options to control its
1560 behavior. It can follow symbolic links if the C<follow> option is
1561 specified. Enabling the C<no_chdir> option will make File::Find skip
1562 changing the current directory when walking directories. The C<untaint>
1563 flag can be useful when running with taint checks enabled.
1569 This extension implements BSD-style file globbing. By default,
1570 it will also be used for the internal implementation of the glob()
1571 operator. See L<File::Glob>.
1575 New methods have been added to the File::Spec module: devnull() returns
1576 the name of the null device (/dev/null on Unix) and tmpdir() the name of
1577 the temp directory (normally /tmp on Unix). There are now also methods
1578 to convert between absolute and relative filenames: abs2rel() and
1579 rel2abs(). For compatibility with operating systems that specify volume
1580 names in file paths, the splitpath(), splitdir(), and catdir() methods
1583 =item File::Spec::Functions
1585 The new File::Spec::Functions modules provides a function interface
1586 to the File::Spec module. Allows shorthand
1588 $fullname = catfile($dir1, $dir2, $file);
1592 $fullname = File::Spec->catfile($dir1, $dir2, $file);
1596 Getopt::Long licensing has changed to allow the Perl Artistic License
1597 as well as the GPL. It used to be GPL only, which got in the way of
1598 non-GPL applications that wanted to use Getopt::Long.
1600 Getopt::Long encourages the use of Pod::Usage to produce help
1601 messages. For example:
1607 GetOptions('help|?' => \$help, man => \$man) or pod2usage(2);
1608 pod2usage(1) if $help;
1609 pod2usage(-exitstatus => 0, -verbose => 2) if $man;
1615 sample - Using GetOpt::Long and Pod::Usage
1619 sample [options] [file ...]
1622 -help brief help message
1623 -man full documentation
1631 Print a brief help message and exits.
1635 Prints the manual page and exits.
1641 B<This program> will read the given input file(s) and do someting
1642 useful with the contents thereof.
1646 See L<Pod::Usage> for details.
1648 A bug that prevented the non-option call-back <> from being
1649 specified as the first argument has been fixed.
1651 To specify the characters < and > as option starters, use ><. Note,
1652 however, that changing option starters is strongly deprecated.
1656 write() and syswrite() will now accept a single-argument
1657 form of the call, for consistency with Perl's syswrite().
1659 You can now create a TCP-based IO::Socket::INET without forcing
1660 a connect attempt. This allows you to configure its options
1661 (like making it non-blocking) and then call connect() manually.
1663 A bug that prevented the IO::Socket::protocol() accessor
1664 from ever returning the correct value has been corrected.
1666 IO::Socket::connect now uses non-blocking IO instead of alarm()
1667 to do connect timeouts.
1669 IO::Socket::accept now uses select() instead of alarm() for doing
1672 IO::Socket::INET->new now sets $! correctly on failure. $@ is
1673 still set for backwards compatability.
1677 Java Perl Lingo is now distributed with Perl. See jpl/README
1678 for more information.
1682 C<use lib> now weeds out any trailing duplicate entries.
1683 C<no lib> removes all named entries.
1687 The bitwise operations C<<< << >>>, C<<< >> >>>, C<&>, C<|>,
1688 and C<~> are now supported on bigints.
1692 The accessor methods Re, Im, arg, abs, rho, and theta can now also
1693 act as mutators (accessor $z->Re(), mutator $z->Re(3)).
1697 A little bit of radial trigonometry (cylindrical and spherical),
1698 radial coordinate conversions, and the great circle distance were added.
1700 =item Pod::Parser, Pod::InputObjects
1702 Pod::Parser is a base class for parsing and selecting sections of
1703 pod documentation from an input stream. This module takes care of
1704 identifying pod paragraphs and commands in the input and hands off the
1705 parsed paragraphs and commands to user-defined methods which are free
1706 to interpret or translate them as they see fit.
1708 Pod::InputObjects defines some input objects needed by Pod::Parser, and
1709 for advanced users of Pod::Parser that need more about a command besides
1712 As of release 5.6 of Perl, Pod::Parser is now the officially sanctioned
1713 "base parser code" recommended for use by all pod2xxx translators.
1714 Pod::Text (pod2text) and Pod::Man (pod2man) have already been converted
1715 to use Pod::Parser and efforts to convert Pod::HTML (pod2html) are already
1716 underway. For any questions or comments about pod parsing and translating
1717 issues and utilities, please use the pod-people@perl.org mailing list.
1719 For further information, please see L<Pod::Parser> and L<Pod::InputObjects>.
1721 =item Pod::Checker, podchecker
1723 This utility checks pod files for correct syntax, according to
1724 L<perlpod>. Obvious errors are flagged as such, while warnings are
1725 printed for mistakes that can be handled gracefully. The checklist is
1726 not complete yet. See L<Pod::Checker>.
1728 =item Pod::ParseUtils, Pod::Find
1730 These modules provide a set of gizmos that are useful mainly for pod
1731 translators. L<Pod::Find|Pod::Find> traverses directory structures and
1732 returns found pod files, along with their canonical names (like
1733 C<File::Spec::Unix>). L<Pod::ParseUtils|Pod::ParseUtils> contains
1734 B<Pod::List> (useful for storing pod list information), B<Pod::Hyperlink>
1735 (for parsing the contents of C<LE<lt>E<gt>> sequences) and B<Pod::Cache>
1736 (for caching information about pod files, e.g. link nodes).
1738 =item Pod::Select, podselect
1740 Pod::Select is a subclass of Pod::Parser which provides a function
1741 named "podselect()" to filter out user-specified sections of raw pod
1742 documentation from an input stream. podselect is a script that provides
1743 access to Pod::Select from other scripts to be used as a filter.
1746 =item Pod::Usage, pod2usage
1748 Pod::Usage provides the function "pod2usage()" to print usage messages for
1749 a Perl script based on its embedded pod documentation. The pod2usage()
1750 function is generally useful to all script authors since it lets them
1751 write and maintain a single source (the pods) for documentation, thus
1752 removing the need to create and maintain redundant usage message text
1753 consisting of information already in the pods.
1755 There is also a pod2usage script which can be used from other kinds of
1756 scripts to print usage messages from pods (even for non-Perl scripts
1757 with pods embedded in comments).
1759 For details and examples, please see L<Pod::Usage>.
1761 =item Pod::Text and Pod::Man
1763 [TODO - Russ Allbery <rra@stanford.edu>]
1767 An EXISTS method has been added to this module (and sdbm_exists() has
1768 been added to the underlying sdbm library), so one can now call exists
1769 on an SDBM_File tied hash and get the correct result, rather than a
1772 A bug that may have caused data loss when more than one disk block
1773 happens to be read from the database in a single FETCH() has been
1778 Sys::Syslog now uses XSUBs to access facilities from syslog.h so it
1779 no longer requires syslog.ph to exist.
1783 Sys::Hostname now uses XSUBs to call the C library's gethostname() or
1784 uname() if they exist.
1788 The timelocal() and timegm() functions used to silently return bogus
1789 results when the date fell outside the machine's integer range. They
1790 now consistently croak() if the date falls in an unsupported range.
1794 The error return value in list context has been changed for all functions
1795 that return a list of values. Previously these functions returned a list
1796 with a single element C<undef> if an error occurred. Now these functions
1797 return the empty list in these situations. This applies to the following
1803 The remaining functions are unchanged and continue to return C<undef> on
1804 error even in list context.
1806 The Win32::SetLastError(ERROR) function has been added as a complement
1807 to the Win32::GetLastError() function.
1809 The new Win32::GetFullPathName(FILENAME) returns the full absolute
1810 pathname for FILENAME in scalar context. In list context it returns
1811 a two-element list containing the fully qualified directory name and
1812 the filename. See L<Win32>.
1816 A new feature called "DBM Filters" has been added to all the
1817 DBM modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File.
1818 DBM Filters add four new methods to each DBM module:
1825 These can be used to filter key-value pairs before the pairs are
1826 written to the database or just after they are read from the database.
1827 See L<perldbmfilter> for further information.
1833 C<use attrs> is now obsolete, and is only provided for
1834 backward-compatibility. It's been replaced by the C<sub : attributes>
1835 syntax. See L<perlsub/"Subroutine Attributes"> and L<attributes>.
1837 C<use utf8> to enable UTF-8 and Unicode support.
1839 Lexical warnings pragma, C<use warnings;>, to control optional warnings.
1842 C<use filetest> to control the behaviour of filetests (C<-r> C<-w>
1843 ...). Currently only one subpragma implemented, "use filetest
1844 'access';", that uses access(2) or equivalent to check permissions
1845 instead of using stat(2) as usual. This matters in filesystems
1846 where there are ACLs (access control lists): the stat(2) might lie,
1847 but access(2) knows better.
1849 =head1 Utility Changes
1853 [TODO - Kurt Starsinic <kstar@chapin.edu>]
1857 C<perlcc> now supports the C and Bytecode backends. By default,
1858 it generates output from the simple C backend rather than the
1859 optimized C backend.
1861 Support for non-Unix platforms has been improved.
1866 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1868 =head1 Documentation Changes
1874 The official list of public Perl API functions.
1876 =item perlcompile.pod
1878 An introduction to using the Perl Compiler suite.
1880 =item perlfilter.pod
1882 An introduction to writing Perl source filters.
1886 Some guidelines for hacking the Perl source code.
1888 =item perlintern.pod
1890 A list of internal functions in the Perl source code.
1891 (List is currently empty.)
1893 =item perlopentut.pod
1895 A tutorial on using open() effectively.
1897 =item perlreftut.pod
1899 A tutorial that introduces the essentials of references.
1903 A tutorial for beginners on object-oriented Perl.
1907 A tutorial on managing class data for object modules.
1909 =item perlunicode.pod
1911 An introduction to Unicode support features in Perl.
1915 =head1 New or Changed Diagnostics
1919 =item "%s" variable %s masks earlier declaration in same %s
1921 (W) A "my" or "our" variable has been redeclared in the current scope or statement,
1922 effectively eliminating all access to the previous instance. This is almost
1923 always a typographical error. Note that the earlier variable will still exist
1924 until the end of the scope or until all closure referents to it are
1927 =item "my sub" not yet implemented
1929 (F) Lexically scoped subroutines are not yet implemented. Don't try that
1932 =item "our" variable %s redeclared
1934 (W) You seem to have already declared the same global once before in the
1935 current lexical scope.
1937 =item '!' allowed only after types %s
1939 (F) The '!' is allowed in pack() and unpack() only after certain types.
1940 See L<perlfunc/pack>.
1942 =item / cannot take a count
1944 (F) You had an unpack template indicating a counted-length string,
1945 but you have also specified an explicit size for the string.
1946 See L<perlfunc/pack>.
1948 =item / must be followed by a, A or Z
1950 (F) You had an unpack template indicating a counted-length string,
1951 which must be followed by one of the letters a, A or Z
1952 to indicate what sort of string is to be unpacked.
1953 See L<perlfunc/pack>.
1955 =item / must be followed by a*, A* or Z*
1957 (F) You had a pack template indicating a counted-length string,
1958 Currently the only things that can have their length counted are a*, A* or Z*.
1959 See L<perlfunc/pack>.
1961 =item / must follow a numeric type
1963 (F) You had an unpack template that contained a '#',
1964 but this did not follow some numeric unpack specification.
1965 See L<perlfunc/pack>.
1967 =item /%s/: Unrecognized escape \\%c passed through
1969 (W) You used a backslash-character combination which is not recognized
1970 by Perl. This combination appears in an interpolated variable or a
1971 C<'>-delimited regular expression. The character was understood literally.
1973 =item /%s/: Unrecognized escape \\%c in character class passed through
1975 (W) You used a backslash-character combination which is not recognized
1976 by Perl inside character classes. The character was understood literally.
1978 =item /%s/ should probably be written as "%s"
1980 (W) You have used a pattern where Perl expected to find a string,
1981 as in the first argument to C<join>. Perl will treat the true
1982 or false result of matching the pattern against $_ as the string,
1983 which is probably not what you had in mind.
1985 =item %s() called too early to check prototype
1987 (W) You've called a function that has a prototype before the parser saw a
1988 definition or declaration for it, and Perl could not check that the call
1989 conforms to the prototype. You need to either add an early prototype
1990 declaration for the subroutine in question, or move the subroutine
1991 definition ahead of the call to get proper prototype checking. Alternatively,
1992 if you are certain that you're calling the function correctly, you may put
1993 an ampersand before the name to avoid the warning. See L<perlsub>.
1995 =item %s argument is not a HASH or ARRAY element
1997 (F) The argument to exists() must be a hash or array element, such as:
2000 $ref->[12]->["susie"]
2002 =item %s argument is not a HASH or ARRAY element or slice
2004 (F) The argument to delete() must be either a hash or array element, such as:
2007 $ref->[12]->["susie"]
2009 or a hash or array slice, such as:
2011 @foo[$bar, $baz, $xyzzy]
2012 @{$ref->[12]}{"susie", "queue"}
2014 =item %s argument is not a subroutine name
2016 (F) The argument to exists() for C<exists &sub> must be a subroutine
2017 name, and not a subroutine call. C<exists &sub()> will generate this error.
2019 =item %s package attribute may clash with future reserved word: %s
2021 (W) A lowercase attribute name was used that had a package-specific handler.
2022 That name might have a meaning to Perl itself some day, even though it
2023 doesn't yet. Perhaps you should use a mixed-case attribute name, instead.
2026 =item (in cleanup) %s
2028 (W) This prefix usually indicates that a DESTROY() method raised
2029 the indicated exception. Since destructors are usually called by
2030 the system at arbitrary points during execution, and often a vast
2031 number of times, the warning is issued only once for any number
2032 of failures that would otherwise result in the same message being
2035 Failure of user callbacks dispatched using the C<G_KEEPERR> flag
2036 could also result in this warning. See L<perlcall/G_KEEPERR>.
2038 =item <> should be quotes
2040 (F) You wrote C<< require <file> >> when you should have written
2043 =item Attempt to join self
2045 (F) You tried to join a thread from within itself, which is an
2046 impossible task. You may be joining the wrong thread, or you may
2047 need to move the join() to some other thread.
2049 =item Bad evalled substitution pattern
2051 (F) You've used the /e switch to evaluate the replacement for a
2052 substitution, but perl found a syntax error in the code to evaluate,
2053 most likely an unexpected right brace '}'.
2055 =item Bad realloc() ignored
2057 (S) An internal routine called realloc() on something that had never been
2058 malloc()ed in the first place. Mandatory, but can be disabled by
2059 setting environment variable C<PERL_BADFREE> to 1.
2061 =item Bareword found in conditional
2063 (W) The compiler found a bareword where it expected a conditional,
2064 which often indicates that an || or && was parsed as part of the
2065 last argument of the previous construct, for example:
2069 It may also indicate a misspelled constant that has been interpreted
2072 use constant TYPO => 1;
2073 if (TYOP) { print "foo" }
2075 The C<strict> pragma is useful in avoiding such errors.
2077 =item Binary number > 0b11111111111111111111111111111111 non-portable
2079 (W) The binary number you specified is larger than 2**32-1
2080 (4294967295) and therefore non-portable between systems. See
2081 L<perlport> for more on portability concerns.
2083 =item Bit vector size > 32 non-portable
2085 (W) Using bit vector sizes larger than 32 is non-portable.
2087 =item Buffer overflow in prime_env_iter: %s
2089 (W) A warning peculiar to VMS. While Perl was preparing to iterate over
2090 %ENV, it encountered a logical name or symbol definition which was too long,
2091 so it was truncated to the string shown.
2093 =item Can't check filesystem of script "%s"
2095 (P) For some reason you can't check the filesystem of the script for nosuid.
2097 =item Can't declare class for non-scalar %s in "%s"
2099 (S) Currently, only scalar variables can declared with a specific class
2100 qualifier in a "my" or "our" declaration. The semantics may be extended
2101 for other types of variables in future.
2103 =item Can't declare %s in "%s"
2105 (F) Only scalar, array, and hash variables may be declared as "my" or
2106 "our" variables. They must have ordinary identifiers as names.
2108 =item Can't ignore signal CHLD, forcing to default
2110 (W) Perl has detected that it is being run with the SIGCHLD signal
2111 (sometimes known as SIGCLD) disabled. Since disabling this signal
2112 will interfere with proper determination of exit status of child
2113 processes, Perl has reset the signal to its default value.
2114 This situation typically indicates that the parent program under
2115 which Perl may be running (e.g. cron) is being very careless.
2117 =item Can't modify non-lvalue subroutine call
2119 (F) Subroutines meant to be used in lvalue context should be declared as
2120 such, see L<perlsub/"Lvalue subroutines">.
2122 =item Can't read CRTL environ
2124 (S) A warning peculiar to VMS. Perl tried to read an element of %ENV
2125 from the CRTL's internal environment array and discovered the array was
2126 missing. You need to figure out where your CRTL misplaced its environ
2127 or define F<PERL_ENV_TABLES> (see L<perlvms>) so that environ is not searched.
2129 =item Can't remove %s: %s, skipping file
2131 (S) You requested an inplace edit without creating a backup file. Perl
2132 was unable to remove the original file to replace it with the modified
2133 file. The file was left unmodified.
2135 =item Can't return %s from lvalue subroutine
2137 (F) Perl detected an attempt to return illegal lvalues (such
2138 as temporary or readonly values) from a subroutine used as an lvalue.
2139 This is not allowed.
2141 =item Can't weaken a nonreference
2143 (F) You attempted to weaken something that was not a reference. Only
2144 references can be weakened.
2146 =item Character class [:%s:] unknown
2148 (F) The class in the character class [: :] syntax is unknown.
2151 =item Character class syntax [%s] belongs inside character classes
2153 (W) The character class constructs [: :], [= =], and [. .] go
2154 I<inside> character classes, the [] are part of the construct,
2155 for example: /[012[:alpha:]345]/. Note that [= =] and [. .]
2156 are not currently implemented; they are simply placeholders for
2159 =item Constant is not %s reference
2161 (F) A constant value (perhaps declared using the C<use constant> pragma)
2162 is being dereferenced, but it amounts to the wrong type of reference. The
2163 message indicates the type of reference that was expected. This usually
2164 indicates a syntax error in dereferencing the constant value.
2165 See L<perlsub/"Constant Functions"> and L<constant>.
2167 =item constant(%s): %%^H is not localized
2169 (F) When setting compile-time-lexicalized hash %^H one should set the
2170 corresponding bit of $^H as well.
2172 =item constant(%s): %s
2174 (F) Compile-time-substitutions (such as overloaded constants and
2175 character names) were not correctly set up.
2177 =item defined(@array) is deprecated
2179 (D) defined() is not usually useful on arrays because it checks for an
2180 undefined I<scalar> value. If you want to see if the array is empty,
2181 just use C<if (@array) { # not empty }> for example.
2183 =item defined(%hash) is deprecated
2185 (D) defined() is not usually useful on hashes because it checks for an
2186 undefined I<scalar> value. If you want to see if the hash is empty,
2187 just use C<if (%hash) { # not empty }> for example.
2189 =item Did not produce a valid header
2193 =item Did you mean "local" instead of "our"?
2195 (W) Remember that "our" does not localize the declared global variable.
2196 You have declared it again in the same lexical scope, which seems superfluous.
2198 =item Document contains no data
2202 =item entering effective %s failed
2204 (F) While under the C<use filetest> pragma, switching the real and
2205 effective uids or gids failed.
2207 =item false [] range "%s" in regexp
2209 (W) A character class range must start and end at a literal character, not
2210 another character class like C<\d> or C<[:alpha:]>. The "-" in your false
2211 range is interpreted as a literal "-". Consider quoting the "-", "\-".
2214 =item Filehandle %s opened only for output
2216 (W) You tried to read from a filehandle opened only for writing. If you
2217 intended it to be a read/write filehandle, you needed to open it with
2218 "+<" or "+>" or "+>>" instead of with "<" or nothing. If
2219 you intended only to read from the file, use "<". See
2222 =item flock() on closed filehandle %s
2224 (W) The filehandle you're attempting to flock() got itself closed some
2225 time before now. Check your logic flow. flock() operates on filehandles.
2226 Are you attempting to call flock() on a dirhandle by the same name?
2228 =item Global symbol "%s" requires explicit package name
2230 (F) You've said "use strict vars", which indicates that all variables
2231 must either be lexically scoped (using "my"), declared beforehand using
2232 "our", or explicitly qualified to say which package the global variable
2235 =item Hexadecimal number > 0xffffffff non-portable
2237 (W) The hexadecimal number you specified is larger than 2**32-1
2238 (4294967295) and therefore non-portable between systems. See
2239 L<perlport> for more on portability concerns.
2241 =item Ill-formed CRTL environ value "%s"
2243 (W) A warning peculiar to VMS. Perl tried to read the CRTL's internal
2244 environ array, and encountered an element without the C<=> delimiter
2245 used to spearate keys from values. The element is ignored.
2247 =item Ill-formed message in prime_env_iter: |%s|
2249 (W) A warning peculiar to VMS. Perl tried to read a logical name
2250 or CLI symbol definition when preparing to iterate over %ENV, and
2251 didn't see the expected delimiter between key and value, so the
2254 =item Illegal binary digit %s
2256 (F) You used a digit other than 0 or 1 in a binary number.
2258 =item Illegal binary digit %s ignored
2260 (W) You may have tried to use a digit other than 0 or 1 in a binary number.
2261 Interpretation of the binary number stopped before the offending digit.
2263 =item Illegal number of bits in vec
2265 (F) The number of bits in vec() (the third argument) must be a power of
2266 two from 1 to 32 (or 64, if your platform supports that).
2268 =item Integer overflow in %s number
2270 (W) The hexadecimal, octal or binary number you have specified either
2271 as a literal or as an argument to hex() or oct() is too big for your
2272 architecture, and has been converted to a floating point number. On a
2273 32-bit architecture the largest hexadecimal, octal or binary number
2274 representable without overflow is 0xFFFFFFFF, 037777777777, or
2275 0b11111111111111111111111111111111 respectively. Note that Perl
2276 transparently promotes all numbers to a floating point representation
2277 internally--subject to loss of precision errors in subsequent
2280 =item Invalid %s attribute: %s
2282 The indicated attribute for a subroutine or variable was not recognized
2283 by Perl or by a user-supplied handler. See L<attributes>.
2285 =item Invalid %s attributes: %s
2287 The indicated attributes for a subroutine or variable were not recognized
2288 by Perl or by a user-supplied handler. See L<attributes>.
2290 =item invalid [] range "%s" in regexp
2292 The offending range is now explicitly displayed.
2294 =item Invalid separator character %s in attribute list
2296 (F) Something other than a colon or whitespace was seen between the
2297 elements of an attribute list. If the previous attribute
2298 had a parenthesised parameter list, perhaps that list was terminated
2299 too soon. See L<attributes>.
2301 =item Invalid separator character %s in subroutine attribute list
2303 (F) Something other than a colon or whitespace was seen between the
2304 elements of a subroutine attribute list. If the previous attribute
2305 had a parenthesised parameter list, perhaps that list was terminated
2308 =item leaving effective %s failed
2310 (F) While under the C<use filetest> pragma, switching the real and
2311 effective uids or gids failed.
2313 =item Lvalue subs returning %s not implemented yet
2315 (F) Due to limitations in the current implementation, array and hash
2316 values cannot be returned in subroutines used in lvalue context.
2317 See L<perlsub/"Lvalue subroutines">.
2319 =item Method %s not permitted
2323 =item Missing %sbrace%s on \N{}
2325 (F) Wrong syntax of character name literal C<\N{charname}> within
2326 double-quotish context.
2328 =item Missing command in piped open
2330 (W) You used the C<open(FH, "| command")> or C<open(FH, "command |")>
2331 construction, but the command was missing or blank.
2333 =item Missing name in "my sub"
2335 (F) The reserved syntax for lexically scoped subroutines requires that they
2336 have a name with which they can be found.
2338 =item No %s specified for -%c
2340 (F) The indicated command line switch needs a mandatory argument, but
2341 you haven't specified one.
2343 =item No package name allowed for variable %s in "our"
2345 (F) Fully qualified variable names are not allowed in "our" declarations,
2346 because that doesn't make much sense under existing semantics. Such
2347 syntax is reserved for future extensions.
2349 =item No space allowed after -%c
2351 (F) The argument to the indicated command line switch must follow immediately
2352 after the switch, without intervening spaces.
2354 =item no UTC offset information; assuming local time is UTC
2356 (S) A warning peculiar to VMS. Perl was unable to find the local
2357 timezone offset, so it's assuming that local system time is equivalent
2358 to UTC. If it's not, define the logical name F<SYS$TIMEZONE_DIFFERENTIAL>
2359 to translate to the number of seconds which need to be added to UTC to
2362 =item Octal number > 037777777777 non-portable
2364 (W) The octal number you specified is larger than 2**32-1 (4294967295)
2365 and therefore non-portable between systems. See L<perlport> for more
2366 on portability concerns.
2368 See also L<perlport> for writing portable code.
2370 =item panic: del_backref
2372 (P) Failed an internal consistency check while trying to reset a weak
2375 =item panic: kid popen errno read
2377 (F) forked child returned an incomprehensible message about its errno.
2379 =item panic: magic_killbackrefs
2381 (P) Failed an internal consistency check while trying to reset all weak
2382 references to an object.
2384 =item Parentheses missing around "%s" list
2386 (W) You said something like
2392 my ($foo, $bar) = @_;
2394 Remember that "my", "our", and "local" bind tighter than comma.
2396 =item Possible Y2K bug: %s
2398 (W) You are concatenating the number 19 with another number, which
2399 could be a potential Year 2000 problem.
2401 =item Premature end of script headers
2405 =item Repeat count in pack overflows
2407 (F) You can't specify a repeat count so large that it overflows
2408 your signed integers. See L<perlfunc/pack>.
2410 =item Repeat count in unpack overflows
2412 (F) You can't specify a repeat count so large that it overflows
2413 your signed integers. See L<perlfunc/unpack>.
2415 =item realloc() of freed memory ignored
2417 (S) An internal routine called realloc() on something that had already
2420 =item Reference is already weak
2422 (W) You have attempted to weaken a reference that is already weak.
2423 Doing so has no effect.
2425 =item setpgrp can't take arguments
2427 (F) Your system has the setpgrp() from BSD 4.2, which takes no arguments,
2428 unlike POSIX setpgid(), which takes a process ID and process group ID.
2430 =item Strange *+?{} on zero-length expression
2432 (W) You applied a regular expression quantifier in a place where it
2433 makes no sense, such as on a zero-width assertion.
2434 Try putting the quantifier inside the assertion instead. For example,
2435 the way to match "abc" provided that it is followed by three
2436 repetitions of "xyz" is C</abc(?=(?:xyz){3})/>, not C</abc(?=xyz){3}/>.
2438 =item switching effective %s is not implemented
2440 (F) While under the C<use filetest> pragma, we cannot switch the
2441 real and effective uids or gids.
2443 =item This Perl can't reset CRTL environ elements (%s)
2445 =item This Perl can't set CRTL environ elements (%s=%s)
2447 (W) Warnings peculiar to VMS. You tried to change or delete an element
2448 of the CRTL's internal environ array, but your copy of Perl wasn't
2449 built with a CRTL that contained the setenv() function. You'll need to
2450 rebuild Perl with a CRTL that does, or redefine F<PERL_ENV_TABLES> (see
2451 L<perlvms>) so that the environ array isn't the target of the change to
2452 %ENV which produced the warning.
2454 =item Unknown open() mode '%s'
2456 (F) The second argument of 3-argument open() is not among the list
2457 of valid modes: C<< < >>, C<< > >>, C<<< >> >>>, C<< +< >>,
2458 C<< +> >>, C<<< +>> >>>, C<-|>, C<|->.
2460 =item Unknown process %x sent message to prime_env_iter: %s
2462 (P) An error peculiar to VMS. Perl was reading values for %ENV before
2463 iterating over it, and someone else stuck a message in the stream of
2464 data Perl expected. Someone's very confused, or perhaps trying to
2465 subvert Perl's population of %ENV for nefarious purposes.
2467 =item Unrecognized escape \\%c passed through
2469 (W) You used a backslash-character combination which is not recognized
2470 by Perl. The character was understood literally.
2472 =item Unterminated attribute parameter in attribute list
2474 (F) The lexer saw an opening (left) parenthesis character while parsing an
2475 attribute list, but the matching closing (right) parenthesis
2476 character was not found. You may need to add (or remove) a backslash
2477 character to get your parentheses to balance. See L<attributes>.
2479 =item Unterminated attribute list
2481 (F) The lexer found something other than a simple identifier at the start
2482 of an attribute, and it wasn't a semicolon or the start of a
2483 block. Perhaps you terminated the parameter list of the previous attribute
2484 too soon. See L<attributes>.
2486 =item Unterminated attribute parameter in subroutine attribute list
2488 (F) The lexer saw an opening (left) parenthesis character while parsing a
2489 subroutine attribute list, but the matching closing (right) parenthesis
2490 character was not found. You may need to add (or remove) a backslash
2491 character to get your parentheses to balance.
2493 =item Unterminated subroutine attribute list
2495 (F) The lexer found something other than a simple identifier at the start
2496 of a subroutine attribute, and it wasn't a semicolon or the start of a
2497 block. Perhaps you terminated the parameter list of the previous attribute
2500 =item Value of CLI symbol "%s" too long
2502 (W) A warning peculiar to VMS. Perl tried to read the value of an %ENV
2503 element from a CLI symbol table, and found a resultant string longer
2504 than 1024 characters. The return value has been truncated to 1024
2507 =item Version number must be a constant number
2509 (P) The attempt to translate a C<use Module n.n LIST> statement into
2510 its equivalent C<BEGIN> block found an internal inconsistency with
2515 =head1 Obsolete Diagnostics
2519 =item Character class syntax [: :] is reserved for future extensions
2521 (W) Within regular expression character classes ([]) the syntax beginning
2522 with "[:" and ending with ":]" is reserved for future extensions.
2523 If you need to represent those character sequences inside a regular
2524 expression character class, just quote the square brackets with the
2525 backslash: "\[:" and ":\]".
2527 =item Ill-formed logical name |%s| in prime_env_iter
2529 (W) A warning peculiar to VMS. A logical name was encountered when preparing
2530 to iterate over %ENV which violates the syntactic rules governing logical
2531 names. Because it cannot be translated normally, it is skipped, and will not
2532 appear in %ENV. This may be a benign occurrence, as some software packages
2533 might directly modify logical name tables and introduce nonstandard names,
2534 or it may indicate that a logical name table has been corrupted.
2536 =item Probable precedence problem on %s
2538 (W) The compiler found a bareword where it expected a conditional,
2539 which often indicates that an || or && was parsed as part of the
2540 last argument of the previous construct, for example:
2544 =item regexp too big
2546 (F) The current implementation of regular expressions uses shorts as
2547 address offsets within a string. Unfortunately this means that if
2548 the regular expression compiles to longer than 32767, it'll blow up.
2549 Usually when you want a regular expression this big, there is a better
2550 way to do it with multiple statements. See L<perlre>.
2552 =item Use of "$$<digit>" to mean "${$}<digit>" is deprecated
2554 (D) Perl versions before 5.004 misinterpreted any type marker followed
2555 by "$" and a digit. For example, "$$0" was incorrectly taken to mean
2556 "${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004.
2558 However, the developers of Perl 5.004 could not fix this bug completely,
2559 because at least two widely-used modules depend on the old meaning of
2560 "$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the
2561 old (broken) way inside strings; but it generates this message as a
2562 warning. And in Perl 5.005, this special treatment will cease.
2568 If you find what you think is a bug, you might check the
2569 articles recently posted to the comp.lang.perl.misc newsgroup.
2570 There may also be information at http://www.perl.com/perl/, the Perl
2573 If you believe you have an unreported bug, please run the B<perlbug>
2574 program included with your release. Make sure to trim your bug down
2575 to a tiny but sufficient test case. Your bug report, along with the
2576 output of C<perl -V>, will be sent off to perlbug@perl.com to be
2577 analysed by the Perl porting team.
2581 The F<Changes> file for exhaustive details on what changed.
2583 The F<INSTALL> file for how to build Perl.
2585 The F<README> file for general stuff.
2587 The F<Artistic> and F<Copying> files for copyright information.
2591 Written by Gurusamy Sarathy <F<gsar@activestate.com>>, with many
2592 contributions from The Perl Porters.
2594 Send omissions or corrections to <F<perlbug@perl.com>>.