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
301 =head2 Binary Incompatibilities
303 In general, the default build of this release is expected to be binary
304 compatible for extensions built with the 5.005 release or its maintenance
305 versions. However, specific platforms may have broken binary compatibility
306 due to changes in the defaults used in hints files. Therefore, please be
307 sure to always check the platform-specific README files for any notes to
310 The usethreads or usemultiplicity builds are B<not> binary compatible
311 with the corresponding builds in 5.005.
313 On platforms that require an explicit list of exports (AIX, OS/2 and Windows,
314 among others), purely internal symbols such as parser functions and the
315 run time opcodes are not exported by default. Perl 5.005 used to export
316 all functions irrespective of whether they were considered part of the
319 For the full list of public API functions, see L<perlapi>.
321 =head1 Installation and Configuration Improvements
323 =head2 -Dusethreads means something different
325 WARNING: Support for threads continues to be an experimental feature.
326 Interfaces and implementation are subject to sudden and drastic changes.
328 The -Dusethreads flag now enables the experimental interpreter-based thread
329 support by default. To get the flavor of experimental threads that was in
330 5.005 instead, you need to run Configure with "-Dusethreads -Duse5005threads".
332 As of v5.5.640, interpreter-threads support is still lacking a way to
333 create new threads from Perl (i.e., C<use Thread;> will not work with
334 interpreter threads). C<use Thread;> continues to be available when you
335 ask for use5005threads, bugs and all.
337 =head2 New Configure flags
339 The following new flags may be enabled on the Configure command line
340 by running Configure with C<-Dflag>.
343 usethreads useithreads (new interpreter threads: no Perl API yet)
344 usethreads use5005threads (threads as they were in 5.005)
346 use64bitint (equal to now deprecated 'use64bits')
352 usesocks (only SOCKS v5 supported)
354 =head2 Threadedness and 64-bitness now more daring
356 The Configure options enabling the use of threads and the use of
357 64-bitness are now more daring in the sense that they no more have an
358 explicit list of operating systems of known threads/64-bit
359 capabilities. In other words: if your operating system has the
360 necessary APIs and datatypes, you should be able just to go ahead and
361 use them, for threads by Configure -Dusethreads, and for 64 bits
362 either explicitly by Configure -Duse64bitint or implicitly if your
363 system has 64 bit wide datatypes. See also L<"64-bit support">.
367 Some platforms have "long doubles", floating point numbers of even
368 larger range than ordinary "doubles". To enable using long doubles for
369 Perl's scalars, use -Duselongdouble.
373 You can enable both -Duse64bitint and -Dlongdouble by -Dusemorebits.
374 See also L<"64-bit support">.
376 =head2 -Duselargefiles
378 Some platforms support large files, files larger than two gigabytes.
379 See L<"Large file support"> for more information.
381 =head2 installusrbinperl
383 You can use "Configure -Uinstallusrbinperl" which causes installperl
384 to skip installing perl also as /usr/bin/perl. This is useful if you
385 prefer not to modify /usr/bin for some reason or another but harmful
386 because many scripts assume to find Perl in /usr/bin/perl.
390 You can use "Configure -Dusesocks" which causes Perl to probe
391 for the SOCKS (v5, not v4) proxy protocol library,
392 http://www.socks.nec.com/
396 You can "post-edit" the Configure variables using the Configure C<-A>
397 flag. The editing happens immediately after the platform specific
398 hints files have been processed but before the actual configuration
399 process starts. Run C<Configure -h> to find out the full C<-A> syntax.
401 =head2 Enhanced Installation Directories
403 The installation structure has been enriched to improve the support
404 for maintaining multiple versions of perl, to provide locations for
405 vendor-supplied modules, scripts, and manpages, and to ease maintenance
406 of locally-added modules, scripts, and manpages. See the section on
407 Installation Directories in the INSTALL file for complete details.
408 For most users building and installing from source, the defaults should
411 If you previously used C<Configure -Dsitelib> or C<-Dsitearch> to set
412 special values for library directories, you might wish to consider using
413 the new C<-Dsiteprefix> setting instead. Also, if you wish to re-use a
414 config.sh file from an earlier version of perl, you should be sure to
415 check that Configure makes sensible choices for the new directories.
416 See INSTALL for complete details.
420 =head2 Unicode and UTF-8 support
422 Perl can optionally use UTF-8 as its internal representation for character
423 strings. The C<utf8> and C<bytes> pragmas are used to control this support
424 in the current lexical scope. See L<perlunicode>, L<utf8> and L<bytes> for
427 =head2 Interpreter cloning, threads, and concurrency
429 WARNING: This is an experimental feature in a pre-alpha state. Use
432 Perl 5.005_63 introduces the beginnings of support for running multiple
433 interpreters concurrently in different threads. In conjunction with
434 the perl_clone() API call, which can be used to selectively duplicate
435 the state of any given interpreter, it is possible to compile a
436 piece of code once in an interpreter, clone that interpreter
437 one or more times, and run all the resulting interpreters in distinct
440 On Windows, this feature is used to emulate fork() at the interpreter
441 level. See L<perlfork>.
443 This feature is still in evolution. It is eventually meant to be used
444 to selectively clone a subroutine and data reachable from that
445 subroutine in a separate interpreter and run the cloned subroutine
446 in a separate thread. Since there is no shared data between the
447 interpreters, little or no locking will be needed (unless parts of
448 the symbol table are explicitly shared). This is obviously intended
449 to be an easy-to-use replacement for the existing threads support.
451 Support for cloning interpreters and interpreter concurrency can be
452 enabled using the -Dusethreads Configure option (see win32/Makefile for
453 how to enable it on Windows.) The resulting perl executable will be
454 functionally identical to one that was built with -Dmultiplicity, but
455 the perl_clone() API call will only be available in the former.
457 -Dusethreads enables, the cpp macros USE_ITHREADS by default, which enables
458 Perl source code changes that provide a clear separation between the op tree
459 and the data it operates with. The former is considered immutable, and can
460 therefore be shared between an interpreter and all of its clones, while the
461 latter is considered local to each interpreter, and is therefore copied for
464 Note that building Perl with the -Dusemultiplicity Configure option
465 is adequate if you wish to run multiple B<independent> interpreters
466 concurrently in different threads. -Dusethreads only provides the
467 additional functionality of the perl_clone() API call and other
468 support for running B<cloned> interpreters concurrently.
470 =head2 Lexically scoped warning categories
472 You can now control the granularity of warnings emitted by perl at a finer
473 level using the C<use warnings> pragma. See L<warnings> and L<perllexwarn>
476 =head2 Lvalue subroutines
478 WARNING: This is an experimental feature.
481 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>,
482 Tuomas Lukka <lukka@iki.fi>)]
484 =head2 "our" declarations
486 An "our" declaration introduces a value that can be best understood
487 as a lexically scoped symbolic alias to a global variable in the
488 package that was current where the variable was declared. This is
489 mostly useful as an alternative to the C<vars> pragma, but also provides
490 the opportunity to introduce typing and other attributes for such
491 variables. See L<perlfunc/our>.
493 =head2 Support for strings represented as a vector of ordinals
495 Literals of the form C<v1.2.3.4> are now parsed as a string composed of
496 of characters with the specified ordinals. This is an alternative, more
497 readable way to construct (possibly unicode) strings instead of
498 interpolating characters, as in C<"\x{1}\x{2}\x{3}\x{4}">. The leading
499 C<v> may be omitted if there are more than two ordinals, so C<1.2.3> is
500 parsed the same as C<v1.2.3>.
502 Strings written in this form are also useful to represent version "numbers".
503 It is easy to compare such version "numbers" (which are really just plain
504 strings) using any of the usual string comparison operators C<eq>, C<ne>,
505 C<lt>, C<gt>, etc., or perform bitwise string operations on them using C<|>,
508 In conjunction with the new C<$^V> magic variable (which contains
509 the perl version as a string), such literals can be used as a readable way
510 to check if you're running a particular version of Perl:
512 # this will parse in older versions of Perl also
513 if ($^V and $^V gt v5.5.640) {
514 # new features supported
517 C<require> and C<use> also have some special magic to support such literals.
518 They will be interpreted as a version rather than as a module name:
520 require v5.6.0; # croak if $^V lt v5.6.0
521 use v5.6.0; # same, but croaks at compile-time
523 Alternatively, the C<v> may be omitted if there is more than one dot:
528 Also, C<sprintf> and C<printf> support the Perl-specific format flag C<%v>
529 to print ordinals of characters in arbitrary strings:
531 printf "v%vd", $^V; # prints current version, such as "v5.5.650"
532 printf "%*vX", ":", $addr; # formats IPv6 address
533 printf "%*vb", " ", $bits; # displays bitstring
535 See L<perldata/"Scalar value constructors"> for additional information.
537 =head2 Weak references
539 WARNING: This is an experimental feature.
541 In previous versions of Perl, you couldn't cache objects so as
542 to allow them to be deleted if the last reference from outside
543 the cache is deleted. The reference in the cache would hold a
544 reference count on the object and the objects would never be
547 Another familiar problem is with circular references. When an
548 object references itself, its reference count would never go
549 down to zero, and it would not get destroyed until the program
552 Weak references solve this by allowing you to "weaken" any
553 reference, that is, make it not count towards the reference count.
554 When the last non-weak reference to an object is deleted, the object
555 is destroyed and all the weak references to the object are
556 automatically undef-ed.
558 To use this feature, you need the WeakRef package from CPAN, which
559 contains additional documentation.
561 change#3385, also need perlguts documentation
562 [TODO - Tuomas Lukka <lukka@iki.fi>]
564 =head2 File globbing implemented internally
566 WARNING: This is currently an experimental feature. Interfaces and
567 implementation are likely to change.
569 Perl now uses the File::Glob implementation of the glob() operator
570 automatically. This avoids using an external csh process and the
571 problems associated with it.
573 =head2 Binary numbers supported
575 Binary numbers are now supported as literals, in s?printf formats, and
579 printf "The answer is: %b\n", oct("0b101010");
581 =head2 Some arrows may be omitted in calls through references
583 Perl now allows the arrow to be omitted in many constructs
584 involving subroutine calls through references. For example,
585 C<< $foo[10]->('foo') >> may now be written C<$foo[10]('foo')>.
586 This is rather similar to how the arrow may be omitted from
587 C<< $foo[10]->{'foo'} >>. Note however, that the arrow is still
588 required for C<< foo(10)->('bar') >>.
590 =head2 exists() is supported on subroutine names
592 The exists() builtin now works on subroutine names. A subroutine
593 is considered to exist if it has been declared (even if implicitly).
594 See L<perlfunc/exists> for examples.
596 =head2 exists() and delete() are supported on array elements
598 The exists() and delete() builtins now work on simple arrays as well.
599 The behavior is similar to that on hash elements.
601 exists() can be used to check whether an array element has been
602 initialized. This avoids autovivifying array elements that don't exist.
603 If the array is tied, the EXISTS() method in the corresponding tied
604 package will be invoked.
606 delete() may be used to remove an element from the array and return
607 it. The array element at that position returns to its unintialized
608 state, so that testing for the same element with exists() will return
609 false. If the element happens to be the one at the end, the size of
610 the array also shrinks up to the highest element that tests true for
611 exists(), or 0 if none such is found. If the array is tied, the DELETE()
612 method in the corresponding tied package will be invoked.
614 See L<perlfunc/exists> and L<perlfunc/delete> for examples.
616 =head2 syswrite() ease-of-use
618 The length argument of C<syswrite()> has become optional.
620 =head2 File and directory handles can be autovivified
622 Similar to how constructs such as C<< $x->[0] >> autovivify a reference,
623 handle constructors (open(), opendir(), pipe(), socketpair(), sysopen(),
624 socket(), and accept()) now autovivify a file or directory handle
625 if the handle passed to them is an uninitialized scalar variable. This
626 allows the constructs such as C<open(my $fh, ...)> and C<open(local $fh,...)>
627 to be used to create filehandles that will conveniently be closed
628 automatically when the scope ends, provided there are no other references
629 to them. This largely eliminates the need for typeglobs when opening
630 filehandles that must be passed around, as in the following example:
634 or die "Can't open '@_': $!";
639 my $f = myopen("</etc/motd");
641 # $f implicitly closed here
645 =head2 64-bit support
647 NOTE: The Configure flags -Duselonglong and -Duse64bits
648 have been deprecated. Use -Duse64bitint instead.
650 Any platform that has 64-bit integers either (a) natively as longs or
651 ints (b) via special compiler flags (c) using long long are able to
652 use "quads" (64-integers) as follows:
658 constants (decimal, hexadecimal, octal, binary) in the code
662 arguments to oct() and hex()
666 arguments to print(), printf() and sprintf() (flag prefixes ll, L, q)
674 pack() and unpack() "q" and "Q" formats
678 in basic arithmetics: + - * / % (NOTE: operating close to the limits
679 of the integer values may produce surprising results)
683 in bit arithmetics: & | ^ ~ << >> (NOTE: these used to be forced
692 Note that unless you have the case (a) you will have to configure
693 and compile Perl using the -Duse64bitint Configure flag.
695 There are actually two modes of 64-bitness: the first one is achieved
696 using Configure -Duse64bitint and the second one using Configure
697 -Duse64bitall. The difference is that the first one is minimal and
698 the second one maximal. The first one does only as much as is
699 required to get 64-bit integers into Perl (this may mean, for example,
700 using "long longs") while your memory may still be limited to 2
701 gigabytes (because your pointers most likely are 32-bit); the second
702 one goes all the way by attempting to switch also longs (and pointers)
703 being 64-bit. This may create an even more binary incompatible Perl
704 than -Duse64bitint: the resulting executable may not run at all in a
705 CPU-bit box, or you may have to reboot/reconfigure/rebuild your
706 operating system to be 64-bit aware.
708 Natively 64-bit systems like Alpha and Cray need neither -Duse64bitint
711 Last but not least: note that due to Perl's habit of always using
712 floating point numbers the quads are still not true integers.
713 When quads overflow their limits (0...18_446_744_073_709_551_615 unsigned,
714 -9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they
715 are silently promoted to floating point numbers, after which they will
716 start losing precision (their lower digits).
718 =head2 Large file support
720 If you have filesystems that support "large files" (files larger than
721 2 gigabytes), you may now also be able to create and access them from
722 Perl. You have to use Configure -Duselargefiles. Turning on the
723 large file support turns on also the 64-bit support on many platforms.
724 Beware that unless your filesystem also supports "sparse files" seeking
725 to umpteen petabytes may be unadvisable.
727 Note that in addition to requiring a proper file system to do large
728 files you may also need to adjust your per-process (or your
729 per-system, or per-process-group, or per-user-group) maximum filesize
730 limits before running Perl scripts that try to handle large files,
731 especially if you intend to write such files.
733 Finally, in addition to your process/process group maximum filesize
734 limits, you may have quota limits on your filesystems that stop you
735 (your user id or your user group id) from using large files.
737 Adjusting your process/user/group/file system/operating system limits
738 is outside the scope of Perl core language. For process limits, you
739 may try increasing the limits using your shell's limits/limit/ulimit
740 command before running Perl. The BSD::Resource extension (not
741 included with the standard Perl distribution) may also be of use, it
742 offers the getrlimit/setrlimit interface that can be used to adjust
743 process resource usage limits, including the maximum filesize limit.
747 In some systems you may be able to use long doubles to enhance the
748 range and precision of your double precision floating point numbers
749 (that is, Perl's numbers). Use Configure -Duselongdouble to enable
750 this support (if it is available).
754 You can "Configure -Dusemorebits" to turn on both the 64-bit support
755 and the long double support.
757 =head2 Enhanced support for sort() subroutines
759 Perl subroutines with a prototype of C<($$)> and XSUBs in general can
760 now be used as sort subroutines. In either case, the two elements to
761 be compared are passed as normal parameters in @_. See L<perlfunc/sort>.
763 For unprototyped sort subroutines, the historical behavior of passing
764 the elements to be compared as the global variables $a and $b remains
767 =head2 Better syntax checks on parenthesized unary operators
771 print defined(&foo,&bar,&baz);
772 print uc("foo","bar","baz");
775 used to be accidentally allowed in earlier versions, and produced
776 unpredictable behaviour. Some produced ancillary warnings
777 when used in this way; others silently did the wrong thing.
779 The parenthesized forms of most unary operators that expect a single
780 argument now ensure that they are not called with more than one
781 argument, making the cases shown above syntax errors. The usual
784 print defined &foo, &bar, &baz;
785 print uc "foo", "bar", "baz";
788 remains unchanged. See L<perlop>.
790 =head2 POSIX character class syntax [: :] supported
792 For example to match alphabetic characters use /[[:alpha:]]/.
793 See L<perlre> for details.
795 =head2 Improved C<qw//> operator
797 The C<qw//> operator is now evaluated at compile time into a true list
798 instead of being replaced with a run time call to C<split()>. This
799 removes the confusing misbehaviour of C<qw//> in scalar context, which
800 had inherited that behaviour from split().
804 $foo = ($bar) = qw(a b c); print "$foo|$bar\n";
806 now correctly prints "3|a", instead of "2|a".
808 =head2 pack() format 'Z' supported
810 The new format type 'Z' is useful for packing and unpacking null-terminated
811 strings. See L<perlfunc/"pack">.
813 =head2 pack() format modifier '!' supported
815 The new format type modifier '!' is useful for packing and unpacking
816 native shorts, ints, and longs. See L<perlfunc/"pack">.
818 =head2 pack() and unpack() support counted strings
820 The template character '/' can be used to specify a counted string
821 type to be packed or unpacked. See L<perlfunc/"pack">.
823 =head2 Comments in pack() templates
825 The '#' character in a template introduces a comment up to
826 end of the line. This facilitates documentation of pack()
829 =head2 $^X variables may now have names longer than one character
831 Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax
832 error. Now variable names that begin with a control character may be
833 arbitrarily long. However, for compatibility reasons, these variables
834 I<must> be written with explicit braces, as C<${^XY}> for example.
835 C<${^XYZ}> is synonymous with ${"\cXYZ"}. Variable names with more
836 than one control character, such as C<${^XY^Z}>, are illegal.
838 The old syntax has not changed. As before, `^X' may be either a
839 literal control-X character or the two-character sequence `caret' plus
840 `X'. When braces are omitted, the variable name stops after the
841 control character. Thus C<"$^XYZ"> continues to be synonymous with
842 C<$^X . "YZ"> as before.
844 As before, lexical variables may not have names beginning with control
845 characters. As before, variables whose names begin with a control
846 character are always forced to be in package `main'. All such variables
847 are reserved for future extensions, except those that begin with
848 C<^_>, which may be used by user programs and are guaranteed not to
849 acquire special meaning in any future version of Perl.
851 =head2 C<use attrs> implicit in subroutine attributes
853 Formerly, if you wanted to mark a subroutine as being a method call or
854 as requiring an automatic lock() when it is entered, you had to declare
855 that with a C<use attrs> pragma in the body of the subroutine.
856 That can now be accomplished with declaration syntax, like this:
858 sub mymethod : locked method ;
860 sub mymethod : locked method {
864 sub othermethod :locked :method ;
866 sub othermethod :locked :method {
871 (Note how only the first C<:> is mandatory, and whitespace surrounding
872 the C<:> is optional.)
874 F<AutoSplit.pm> and F<SelfLoader.pm> have been updated to keep the attributes
875 with the stubs they provide. See L<attributes>.
877 =head2 Regular expression improvements
879 change#2827,2373,2372,2365,1813,1800,4112,4158,4215,4301
880 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
882 =head2 Overloading improvements
885 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
887 =head2 open() with more than two arguments
889 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
891 =head2 Support for interpolating named characters
894 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
896 =head2 C<require> and C<do> may be overridden
898 C<require> and C<do 'file'> operations may be overridden locally
899 by importing subroutines of the same name into the current package
900 (or globally by importing them into the CORE::GLOBAL:: namespace).
901 Overriding C<require> will also affect C<use>, provided the override
902 is visible at compile-time.
903 See L<perlsub/"Overriding Built-in Functions">.
905 =head2 New variable $^C reflects C<-c> switch
907 C<$^C> has a boolean value that reflects whether perl is being run
908 in compile-only mode (i.e. via the C<-c> switch). Since
909 BEGIN blocks are executed under such conditions, this variable
910 enables perl code to determine whether actions that make sense
911 only during normal running are warranted. See L<perlvar>.
913 =head2 New variable $^V contains Perl version as a string
915 C<$^V> contains the Perl version number as a string composed of
916 characters whose ordinals match the version numbers, e.g., v5.6.0.
917 This may be used in string comparisons.
919 See C<Support for strings represented as a vector of ordinals> for an
922 =head2 Optional Y2K warnings
924 If Perl is built with the cpp macro C<PERL_Y2KWARN> defined,
925 it emits optional warnings when concatenating the number 19
928 This behavior must be specifically enabled when running Configure.
929 See F<INSTALL> and F<README.Y2K>.
931 =head1 Significant bug fixes
933 =head2 <HANDLE> on empty files
935 With C<$/> set to C<undef>, "slurping" an empty file returns a string of
936 zero length (instead of C<undef>, as it used to) the first time the
937 HANDLE is read after C<$/> is set to C<undef>. Further reads yield
940 This means that the following will append "foo" to an empty file (it used
943 perl -0777 -pi -e 's/^/foo/' empty_file
947 perl -pi -e 's/^/foo/' empty_file
949 is unchanged (it continues to leave the file empty).
951 =head2 C<eval '...'> improvements
953 Line numbers (as reflected by caller() and most diagnostics) within
954 C<eval '...'> were often incorrect when here documents were involved.
955 This has been corrected.
957 Lexical lookups for variables appearing in C<eval '...'> within
958 functions that were themselves called within an C<eval '...'> were
959 searching the wrong place for lexicals. The lexical search now
960 correctly ends at the subroutine's block boundary.
962 Parsing of here documents used to be flawed when they appeared as
963 the replacement expression in C<eval 's/.../.../e'>. This has
966 =head2 All compilation errors are true errors
968 Some "errors" encountered at compile time were by neccessity
969 generated as warnings followed by eventual termination of the
970 program. This enabled more such errors to be reported in a
971 single run, rather than causing a hard stop at the first error
972 that was encountered.
974 The mechanism for reporting such errors has been reimplemented
975 to queue compile-time errors and report them at the end of the
976 compilation as true errors rather than as warnings. This fixes
977 cases where error messages leaked through in the form of warnings
978 when code was compiled at run time using C<eval STRING>, and
979 also allows such errors to be reliably trapped using __DIE__ hooks.
981 =head2 Automatic flushing of output buffers
983 fork(), exec(), system(), qx//, and pipe open()s now flush buffers
984 of all files opened for output when the operation
985 was attempted. This mostly eliminates confusing
986 buffering mishaps suffered by users unaware of how Perl internally
989 =head2 Better diagnostics on meaningless filehandle operations
991 Constructs such as C<< open(<FH>) >> and C<< close(<FH>) >>
992 are compile time errors. Attempting to read from filehandles that
993 were opened only for writing will now produce warnings (just as
994 writing to read-only filehandles does).
996 =head2 Where possible, buffered data discarded from duped input filehandle
998 C<< open(NEW, "<&OLD") >> now attempts to discard any data that
999 was previously read and buffered in C<OLD> before duping the handle.
1000 On platforms where doing this is allowed, the next read operation
1001 on C<NEW> will return the same data as the corresponding operation
1002 on C<OLD>. Formerly, it would have returned the data from the start
1003 of the following disk block instead.
1005 =head2 eof() has the same old magic as <>
1007 C<eof()> would return true if no attempt to read from C<< <> >> had
1008 yet been made. C<eof()> has been changed to have a little magic of its
1009 own, it now opens the C<< <> >> files.
1011 =head2 system(), backticks and pipe open now reflect exec() failure
1013 On Unix and similar platforms, system(), qx() and open(FOO, "cmd |")
1014 etc., are implemented via fork() and exec(). When the underlying
1015 exec() fails, earlier versions did not report the error properly,
1016 since the exec() happened to be in a different process.
1018 The child process now communicates with the parent about the
1019 error in launching the external command, which allows these
1020 constructs to return with their usual error value and set $!.
1022 =head2 Implicitly closed filehandles are safer
1024 Sometimes implicitly closed filehandles (as when they are localized,
1025 and Perl automatically closes them on exiting the scope) could
1026 inadvertently set $? or $!. This has been corrected.
1028 =head2 C<(\$)> prototype and C<$foo{a}>
1030 An scalar reference prototype now correctly allows a hash or
1031 array element in that slot.
1033 =head2 Pseudo-hashes work better
1035 Dereferencing some types of reference values in a pseudo-hash,
1036 such as C<< $ph->{foo}[1] >>, was accidentally disallowed. This has
1039 When applied to a pseudo-hash element, exists() now reports whether
1040 the specified value exists, not merely if the key is valid.
1042 delete() now works on pseudo-hashes. When given a pseudo-hash element
1043 or slice it deletes the values corresponding to the keys (but not the keys
1044 themselves). See L<perlref/"Pseudo-hashes: Using an array as a hash">.
1046 Pseudo-hash slices with constant keys are now optimized to array lookups
1049 The C<fields> pragma now provides ways to create pseudo-hashes, via
1050 fields::new() and fields::phash(). See L<fields>.
1052 =head2 C<goto &sub> and AUTOLOAD
1054 The C<goto &sub> construct works correctly when C<&sub> happens
1057 =head2 C<-bareword> allowed under C<use integer>
1059 The autoquoting of barewords preceded by C<-> did not work
1060 in prior versions when the C<integer> pragma was enabled.
1061 This has been fixed.
1063 =head2 Boolean assignment operators are legal lvalues
1065 Constructs such as C<($a ||= 2) += 1> are now allowed.
1067 =head2 C<sort $coderef @foo> allowed
1069 sort() did not accept a subroutine reference as the comparison
1070 function in earlier versions. This is now permitted.
1072 =head2 Failures in DESTROY()
1074 When code in a destructor threw an exception, it went unnoticed
1075 in earlier versions of Perl, unless someone happened to be
1076 looking in $@ just after the point the destructor happened to
1077 run. Such failures are now visible as warnings when warnings are
1080 =head2 Locale bugs fixed
1082 printf() and sprintf() previously reset the numeric locale
1083 back to the default "C" locale. This has been fixed.
1085 Numbers formatted according to the local numeric locale
1086 (such as using a decimal comma instead of a decimal dot) caused
1087 "isn't numeric" warnings, even while the operations accessing
1088 those numbers produced correct results. The warnings are gone.
1092 The C<eval 'return sub {...}'> construct could sometimes leak
1093 memory. This has been fixed.
1095 Operations that aren't filehandle constructors used to leak memory
1096 when used on invalid filehandles. This has been fixed.
1098 Constructs that modified C<@_> could fail to deallocate values
1099 in C<@_> and thus leak memory. This has been corrected.
1101 =head2 Spurious subroutine stubs after failed subroutine calls
1103 Perl could sometimes create empty subroutine stubs when a
1104 subroutine was not found in the package. Such cases stopped
1105 later method lookups from progressing into base packages.
1106 This has been corrected.
1108 =head2 Consistent numeric conversions
1111 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1113 =head2 Taint failures under C<-U>
1115 When running in unsafe mode, taint violations could sometimes
1116 cause silent failures. This has been fixed.
1118 =head2 END blocks and the C<-c> switch
1120 Prior versions used to run BEGIN B<and> END blocks when Perl was
1121 run in compile-only mode. Since this is typically not the expected
1122 behavior, END blocks are not executed anymore when the C<-c> switch
1125 See L<CHECK blocks> for how to run things when the compile phase ends.
1127 =head2 Potential to leak DATA filehandles
1129 Using the C<__DATA__> token creates an implicit filehandle to
1130 the file that contains the token. It is the program's
1131 responsibility to close it when it is done reading from it.
1133 This caveat is now better explained in the documentation.
1136 =head2 Diagnostics follow STDERR
1138 Diagnostic output now goes to whichever file the C<STDERR> handle
1139 is pointing at, instead of always going to the underlying C runtime
1140 library's C<stderr>.
1142 =head2 Other fixes for better diagnostics
1144 Line numbers are no longer suppressed (under most likely circumstances)
1145 during the global destruction phase.
1147 Diagnostics emitted from code running in threads other than the main
1148 thread are now accompanied by the thread ID.
1150 Embedded null characters in diagnostics now actually show up. They
1151 used to truncate the message in prior versions.
1153 $foo::a and $foo::b are now exempt from "possible typo" warnings only
1154 if sort() is encountered in package foo.
1156 Unrecognized alphabetic escapes encountered when parsing quote
1157 constructs now generate a warning, since they may take on new
1158 semantics in later versions of Perl.
1160 =head1 Performance enhancements
1162 =head2 Simple sort() using { $a <=> $b } and the like are optimized
1164 Many common sort() operations using a simple inlined block are now
1165 optimized for faster performance.
1167 =head2 Optimized assignments to lexical variables
1169 Certain operations in the RHS of assignment statements have been
1170 optimized to directly set the lexical variable on the LHS,
1171 eliminating redundant copying overheads.
1173 =head2 Faster mechanism to invoke XSUBs
1176 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1178 =head2 Perl_malloc() improvements
1181 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1183 =head2 Faster subroutine calls
1185 Minor changes in how subroutine calls are handled internally
1186 provide marginal improvements in performance.
1188 =head1 Platform specific changes
1190 =head2 Supported platforms
1196 VM/ESA is now supported.
1200 Siemens BS2000 is now supported under the POSIX Shell.
1204 The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread
1209 GNU/Hurd is now supported.
1213 Rhapsody/Darwin is now supported.
1217 EPOC is is now supported (on Psion 5).
1227 Perl now works with djgpp 2.02 (and 2.03 alpha).
1231 Environment variable names are not converted to uppercase any more.
1235 Wrong exit code from backticks now fixed.
1239 This port is still using its own builtin globbing.
1245 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1247 =head2 OS390 (OpenEdition MVS)
1249 Support for this EBCDIC platform has not been renewed in this release.
1250 There are difficulties in reconciling Perl's standardization on UTF-8
1251 as its internal representation for characters with the EBCDIC character
1252 set, because the two are incompatible.
1254 It is unclear whether future versions will renew support for this
1255 platform, but the possibility exists.
1259 Numerous revisions and extensions to configuration, build, testing, and
1260 installation process to accomodate core changes and VMS-specific options
1262 Expand %ENV-handling code to allow runtime mapping to logical names,
1263 CLI symbols, and CRTL environ array
1265 Extension of subprocess invocation code to accept filespecs as command "verbs"
1267 Add to Perl command line processing the ability to use default file types and
1268 to recognize Unix-style C<2E<gt>&1>.
1270 Expansion of File::Spec::VMS routines, and integration into ExtUtils::MM_VMS
1272 Extension of ExtUtils::MM_VMS to handle complex extensions more flexibly
1274 Barewords at start of Unix-syntax paths may be treated as text rather than
1275 only as logical names
1277 Optional secure translation of several logical names used internally by Perl
1279 Miscellaneous bugfixing and porting of new core code to VMS
1281 Thanks are gladly extended to the many people who have contributed VMS
1282 patches, testing, and ideas.
1286 Site library searches failed to look for ".../site/5.XXX/lib"
1287 if ".../site/5.XXXYY/lib" wasn't found. This has been corrected.
1289 When given a pathname that consists only of a drivename, such
1290 as C<A:>, opendir() and stat() now use the current working
1291 directory for the drive rather than the drive root.
1293 The builtin XSUB functions in the Win32:: namespace are
1294 documented. See L<Win32>.
1296 $^X now contains the full path name of the running executable.
1298 A Win32::GetLongPathName() function is provided to complement
1299 Win32::GetFullPathName() and Win32::GetShortPathName(). See L<Win32>.
1301 POSIX::uname() is supported.
1303 system(1,...) now returns true process IDs rather than process
1304 handles. kill() accepts any real process id, rather than strictly
1305 return values from system(1,...).
1307 For better compatibility with Unix, C<kill(0, $pid)> can now be used to
1308 test whether a process exists.
1310 The C<Shell> module is supported.
1312 Rudimentary support for building under command.com in Windows 95
1315 Scripts are read in binary mode by default to allow ByteLoader (and
1316 the filter mechanism in general) to work properly. For compatibility,
1317 the DATA filehandle will be set to text mode if a carriage return is
1318 detected at the end of the line containing the __END__ or __DATA__
1319 token; if not, the DATA filehandle will be left open in binary mode.
1320 Earlier versions always opened the DATA filehandle in text mode.
1322 The glob() operator is implemented via the C<File::Glob> extension,
1323 which supports glob syntax of the C shell. This increases the flexibility
1324 of the glob() operator, but there may be compatibility issues for
1325 programs that relied on the older globbing syntax. If you want to
1326 preserve compatibility with the older syntax, you might want to put
1327 a C<use File::DosGlob;> in your program. For details and compatibility
1328 information, see L<File::Glob>.
1338 Compatibility tests for C<sub : attrs> vs the older C<use attrs>.
1342 Tests for new environment scalar capability (e.g., C<use Env qw($BAR);>).
1346 Tests for new environment array capability (e.g., C<use Env qw(@PATH);>).
1350 IO constants (SEEK_*, _IO*).
1354 Directory-related IO methods (new, read, close, rewind, tied delete).
1356 =item lib/io_multihomed
1358 INET sockets with multi-homed hosts.
1370 Regression tests for C<my ($x,@y,%z) : attrs> and <sub : attrs>.
1374 File test operators.
1378 Verify operations that access pad objects (lexicals and temporaries).
1382 Verify C<exists &sub> operations.
1386 =head1 Modules and Pragmata
1394 While used internally by Perl as a pragma, this module also
1395 provides a way to fetch subroutine and variable attributes.
1400 WARNING: The Compiler suite is still highly experimental. The
1401 generated code may not be correct, even it manages to execute
1404 The Perl Compiler suite has been extensively reworked for this
1405 release. More of the standard Perl testsuite passes when run
1406 under the Compiler, but there is still a significant way to
1407 go to achieve production quality compiled executables.
1411 The ByteLoader is a dedicated extension to generate and run
1412 Perl bytecode. See L<ByteLoader>.
1416 References can now be used.
1418 The new version also allows a leading underscore in constant names, but
1419 disallows a double leading underscore (as in "__LINE__"). Some other names
1420 are disallowed or warned against, including BEGIN, END, etc. Some names
1421 which were forced into main:: used to fail silently in some cases; now they're
1422 fatal (outside of main::) and an optional warning (inside of main::).
1423 The ability to detect whether a constant had been set with a given name has
1431 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1435 A C<Maxdepth> setting can be specified to avoid venturing
1436 too deeply into deep data structures. See L<Data::Dumper>.
1438 Dumping C<qr//> objects works correctly.
1442 C<DB> is an experimental module that exposes a clean abstraction
1443 to Perl's debugging API.
1447 DB_File can now be built with Berkeley DB versions 1, 2 or 3.
1448 See C<ext/DB_File/Changes>.
1452 Devel::DProf, a Perl source code profiler has been added. See
1453 L<Devel::DProf> and L<dprofpp>.
1457 The Dumpvalue module provides screen dumps of Perl data.
1461 Overall, Benchmark results exhibit lower average error and better timing
1464 You can now run tests for I<n> seconds instead of guessing the right
1465 number of tests to run: e.g. timethese(-5, ...) will run each
1466 code for at least 5 CPU seconds. Zero as the "number of repetitions"
1467 means "for at least 3 CPU seconds". The output format has also
1468 changed. For example:
1470 use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
1472 will now output something like this:
1474 Benchmark: running a, b, each for at least 5 CPU seconds...
1475 a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
1476 b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
1478 New features: "each for at least N CPU seconds...", "wallclock secs",
1479 and the "@ operations/CPU second (n=operations)".
1481 timethese() now returns a reference to a hash of Benchmark objects containing
1482 the test results, keyed on the names of the tests.
1484 timethis() now returns the iterations field in the Benchmark result object
1487 timethese(), timethis(), and the new cmpthese() (see below) can also take
1488 a format specifier of 'none' to suppress output.
1490 A new function countit() is just like timeit() except that it takes a
1491 TIME instead of a COUNT.
1493 A new function cmpthese() prints a chart comparing the results of each test
1494 returned from a timethese() call. For each possible pair of tests, the
1495 percentage speed difference (iters/sec or seconds/iter) is shown.
1497 For other details, see L<Benchmark>.
1501 The Devel::Peek module provides access to the internal representation
1502 of Perl variables and data. It is a data debugging tool for the XS programmer.
1506 $PERL_VERSION now stands for C<$^V> (a string value) rather than for C<$]>
1511 Env now supports accessing environment variables like PATH as array
1514 =item ExtUtils::MakeMaker
1516 change#4135, also needs docs in module pod
1517 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1521 More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for
1522 large file (more than 4GB) access Note that the O_LARGEFILE is
1523 automatically/transparently added to sysopen() flags if large file
1524 support has been configured), Free/Net/OpenBSD locking behaviour flags
1525 F_FLOCK, F_POSIX, Linux F_SHLCK, and O_ACCMODE: the combined mask of
1526 O_RDONLY, O_WRONLY, and O_RDWR. The seek()/sysseek() constants
1527 SEEK_SET, SEEK_CUR, and SEEK_END are available via the C<:seek> tag.
1528 The chmod()/stat() S_IF* constants and S_IS* functions are available
1529 via the C<:mode> tag.
1534 A compare_text() function has been added, which allows custom
1535 comparison functions. See L<File::Compare>.
1539 File::Find now works correctly when the wanted() function is either
1540 autoloaded or is a symbolic reference.
1542 A bug that caused File::Find to lose track of the working directory
1543 when pruning top-level directories has been fixed.
1545 File::Find now also supports several other options to control its
1546 behavior. It can follow symbolic links if the C<follow> option is
1547 specified. Enabling the C<no_chdir> option will make File::Find skip
1548 changing the current directory when walking directories. The C<untaint>
1549 flag can be useful when running with taint checks enabled.
1555 This extension implements BSD-style file globbing. By default,
1556 it will also be used for the internal implementation of the glob()
1557 operator. See L<File::Glob>.
1561 New methods have been added to the File::Spec module: devnull() returns
1562 the name of the null device (/dev/null on Unix) and tmpdir() the name of
1563 the temp directory (normally /tmp on Unix). There are now also methods
1564 to convert between absolute and relative filenames: abs2rel() and
1565 rel2abs(). For compatibility with operating systems that specify volume
1566 names in file paths, the splitpath(), splitdir(), and catdir() methods
1569 =item File::Spec::Functions
1571 The new File::Spec::Functions modules provides a function interface
1572 to the File::Spec module. Allows shorthand
1574 $fullname = catfile($dir1, $dir2, $file);
1578 $fullname = File::Spec->catfile($dir1, $dir2, $file);
1582 Getopt::Long licensing has changed to allow the Perl Artistic License
1583 as well as the GPL. It used to be GPL only, which got in the way of
1584 non-GPL applications that wanted to use Getopt::Long.
1586 Getopt::Long encourages the use of Pod::Usage to produce help
1587 messages. For example:
1593 GetOptions('help|?' => \$help, man => \$man) or pod2usage(2);
1594 pod2usage(1) if $help;
1595 pod2usage(-exitstatus => 0, -verbose => 2) if $man;
1601 sample - Using GetOpt::Long and Pod::Usage
1605 sample [options] [file ...]
1608 -help brief help message
1609 -man full documentation
1617 Print a brief help message and exits.
1621 Prints the manual page and exits.
1627 B<This program> will read the given input file(s) and do someting
1628 useful with the contents thereof.
1632 See L<Pod::Usage> for details.
1634 A bug that prevented the non-option call-back <> from being
1635 specified as the first argument has been fixed.
1637 To specify the characters < and > as option starters, use ><. Note,
1638 however, that changing option starters is strongly deprecated.
1642 write() and syswrite() will now accept a single-argument
1643 form of the call, for consistency with Perl's syswrite().
1645 You can now create a TCP-based IO::Socket::INET without forcing
1646 a connect attempt. This allows you to configure its options
1647 (like making it non-blocking) and then call connect() manually.
1649 A bug that prevented the IO::Socket::protocol() accessor
1650 from ever returning the correct value has been corrected.
1652 IO::Socket::connect now uses non-blocking IO instead of alarm()
1653 to do connect timeouts.
1655 IO::Socket::accept now uses select() instead of alarm() for doing
1658 IO::Socket::INET->new now sets $! correctly on failure. $@ is
1659 still set for backwards compatability.
1663 Java Perl Lingo is now distributed with Perl. See jpl/README
1664 for more information.
1668 C<use lib> now weeds out any trailing duplicate entries.
1669 C<no lib> removes all named entries.
1673 The bitwise operations C<<< << >>>, C<<< >> >>>, C<&>, C<|>,
1674 and C<~> are now supported on bigints.
1678 The accessor methods Re, Im, arg, abs, rho, and theta can now also
1679 act as mutators (accessor $z->Re(), mutator $z->Re(3)).
1683 A little bit of radial trigonometry (cylindrical and spherical),
1684 radial coordinate conversions, and the great circle distance were added.
1686 =item Pod::Parser, Pod::InputObjects
1688 Pod::Parser is a base class for parsing and selecting sections of
1689 pod documentation from an input stream. This module takes care of
1690 identifying pod paragraphs and commands in the input and hands off the
1691 parsed paragraphs and commands to user-defined methods which are free
1692 to interpret or translate them as they see fit.
1694 Pod::InputObjects defines some input objects needed by Pod::Parser, and
1695 for advanced users of Pod::Parser that need more about a command besides
1698 As of release 5.6 of Perl, Pod::Parser is now the officially sanctioned
1699 "base parser code" recommended for use by all pod2xxx translators.
1700 Pod::Text (pod2text) and Pod::Man (pod2man) have already been converted
1701 to use Pod::Parser and efforts to convert Pod::HTML (pod2html) are already
1702 underway. For any questions or comments about pod parsing and translating
1703 issues and utilities, please use the pod-people@perl.org mailing list.
1705 For further information, please see L<Pod::Parser> and L<Pod::InputObjects>.
1707 =item Pod::Checker, podchecker
1709 This utility checks pod files for correct syntax, according to
1710 L<perlpod>. Obvious errors are flagged as such, while warnings are
1711 printed for mistakes that can be handled gracefully. The checklist is
1712 not complete yet. See L<Pod::Checker>.
1714 =item Pod::ParseUtils, Pod::Find
1716 These modules provide a set of gizmos that are useful mainly for pod
1717 translators. L<Pod::Find|Pod::Find> traverses directory structures and
1718 returns found pod files, along with their canonical names (like
1719 C<File::Spec::Unix>). L<Pod::ParseUtils|Pod::ParseUtils> contains
1720 B<Pod::List> (useful for storing pod list information), B<Pod::Hyperlink>
1721 (for parsing the contents of C<LE<lt>E<gt>> sequences) and B<Pod::Cache>
1722 (for caching information about pod files, e.g. link nodes).
1724 =item Pod::Select, podselect
1726 Pod::Select is a subclass of Pod::Parser which provides a function
1727 named "podselect()" to filter out user-specified sections of raw pod
1728 documentation from an input stream. podselect is a script that provides
1729 access to Pod::Select from other scripts to be used as a filter.
1732 =item Pod::Usage, pod2usage
1734 Pod::Usage provides the function "pod2usage()" to print usage messages for
1735 a Perl script based on its embedded pod documentation. The pod2usage()
1736 function is generally useful to all script authors since it lets them
1737 write and maintain a single source (the pods) for documentation, thus
1738 removing the need to create and maintain redundant usage message text
1739 consisting of information already in the pods.
1741 There is also a pod2usage script which can be used from other kinds of
1742 scripts to print usage messages from pods (even for non-Perl scripts
1743 with pods embedded in comments).
1745 For details and examples, please see L<Pod::Usage>.
1747 =item Pod::Text and Pod::Man
1749 Pod::Text has been rewritten to use Pod::Parser. While pod2text() is
1750 still available for backwards compatibility, the module now has a new
1751 preferred interface. See L<Pod::Text> for the details. The new Pod::Text
1752 module is easily subclassed for tweaks to the output, and two such
1753 subclasses (Pod::Text::Termcap for man-page-style bold and underlining
1754 using termcap information, and Pod::Text::Color for markup with ANSI color
1755 sequences) are now standard.
1757 pod2man has been turned into a module, Pod::Man, which also uses
1758 Pod::Parser. In the process, several outstanding bugs related to quotes
1759 in section headers, quoting of code escapes, and nested lists have been
1760 fixed. pod2man is now a wrapper script around this module.
1764 An EXISTS method has been added to this module (and sdbm_exists() has
1765 been added to the underlying sdbm library), so one can now call exists
1766 on an SDBM_File tied hash and get the correct result, rather than a
1769 A bug that may have caused data loss when more than one disk block
1770 happens to be read from the database in a single FETCH() has been
1775 Sys::Syslog now uses XSUBs to access facilities from syslog.h so it
1776 no longer requires syslog.ph to exist.
1780 Sys::Hostname now uses XSUBs to call the C library's gethostname() or
1781 uname() if they exist.
1783 =item Term::ANSIColor
1785 Term::ANSIColor is a very simple module to provide easy and readable
1786 access to the ANSI color and highlighting escape sequences, supported by
1787 most ANSI terminal emulators. It is now included standard.
1791 The timelocal() and timegm() functions used to silently return bogus
1792 results when the date fell outside the machine's integer range. They
1793 now consistently croak() if the date falls in an unsupported range.
1797 The error return value in list context has been changed for all functions
1798 that return a list of values. Previously these functions returned a list
1799 with a single element C<undef> if an error occurred. Now these functions
1800 return the empty list in these situations. This applies to the following
1806 The remaining functions are unchanged and continue to return C<undef> on
1807 error even in list context.
1809 The Win32::SetLastError(ERROR) function has been added as a complement
1810 to the Win32::GetLastError() function.
1812 The new Win32::GetFullPathName(FILENAME) returns the full absolute
1813 pathname for FILENAME in scalar context. In list context it returns
1814 a two-element list containing the fully qualified directory name and
1815 the filename. See L<Win32>.
1819 A new feature called "DBM Filters" has been added to all the
1820 DBM modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File.
1821 DBM Filters add four new methods to each DBM module:
1828 These can be used to filter key-value pairs before the pairs are
1829 written to the database or just after they are read from the database.
1830 See L<perldbmfilter> for further information.
1836 C<use attrs> is now obsolete, and is only provided for
1837 backward-compatibility. It's been replaced by the C<sub : attributes>
1838 syntax. See L<perlsub/"Subroutine Attributes"> and L<attributes>.
1840 C<use utf8> to enable UTF-8 and Unicode support.
1842 Lexical warnings pragma, C<use warnings;>, to control optional warnings.
1845 C<use filetest> to control the behaviour of filetests (C<-r> C<-w>
1846 ...). Currently only one subpragma implemented, "use filetest
1847 'access';", that uses access(2) or equivalent to check permissions
1848 instead of using stat(2) as usual. This matters in filesystems
1849 where there are ACLs (access control lists): the stat(2) might lie,
1850 but access(2) knows better.
1852 =head1 Utility Changes
1856 [TODO - Kurt Starsinic <kstar@chapin.edu>]
1860 C<perlcc> now supports the C and Bytecode backends. By default,
1861 it generates output from the simple C backend rather than the
1862 optimized C backend.
1864 Support for non-Unix platforms has been improved.
1869 [TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1871 =head1 Documentation Changes
1877 The official list of public Perl API functions.
1879 =item perlcompile.pod
1881 An introduction to using the Perl Compiler suite.
1883 =item perlfilter.pod
1885 An introduction to writing Perl source filters.
1889 Some guidelines for hacking the Perl source code.
1891 =item perlintern.pod
1893 A list of internal functions in the Perl source code.
1894 (List is currently empty.)
1896 =item perlopentut.pod
1898 A tutorial on using open() effectively.
1900 =item perlreftut.pod
1902 A tutorial that introduces the essentials of references.
1906 A tutorial for beginners on object-oriented Perl.
1910 A tutorial on managing class data for object modules.
1912 =item perlunicode.pod
1914 An introduction to Unicode support features in Perl.
1918 =head1 New or Changed Diagnostics
1922 =item "%s" variable %s masks earlier declaration in same %s
1924 (W) A "my" or "our" variable has been redeclared in the current scope or statement,
1925 effectively eliminating all access to the previous instance. This is almost
1926 always a typographical error. Note that the earlier variable will still exist
1927 until the end of the scope or until all closure referents to it are
1930 =item "my sub" not yet implemented
1932 (F) Lexically scoped subroutines are not yet implemented. Don't try that
1935 =item "our" variable %s redeclared
1937 (W) You seem to have already declared the same global once before in the
1938 current lexical scope.
1940 =item '!' allowed only after types %s
1942 (F) The '!' is allowed in pack() and unpack() only after certain types.
1943 See L<perlfunc/pack>.
1945 =item / cannot take a count
1947 (F) You had an unpack template indicating a counted-length string,
1948 but you have also specified an explicit size for the string.
1949 See L<perlfunc/pack>.
1951 =item / must be followed by a, A or Z
1953 (F) You had an unpack template indicating a counted-length string,
1954 which must be followed by one of the letters a, A or Z
1955 to indicate what sort of string is to be unpacked.
1956 See L<perlfunc/pack>.
1958 =item / must be followed by a*, A* or Z*
1960 (F) You had a pack template indicating a counted-length string,
1961 Currently the only things that can have their length counted are a*, A* or Z*.
1962 See L<perlfunc/pack>.
1964 =item / must follow a numeric type
1966 (F) You had an unpack template that contained a '#',
1967 but this did not follow some numeric unpack specification.
1968 See L<perlfunc/pack>.
1970 =item /%s/: Unrecognized escape \\%c passed through
1972 (W) You used a backslash-character combination which is not recognized
1973 by Perl. This combination appears in an interpolated variable or a
1974 C<'>-delimited regular expression. The character was understood literally.
1976 =item /%s/: Unrecognized escape \\%c in character class passed through
1978 (W) You used a backslash-character combination which is not recognized
1979 by Perl inside character classes. The character was understood literally.
1981 =item /%s/ should probably be written as "%s"
1983 (W) You have used a pattern where Perl expected to find a string,
1984 as in the first argument to C<join>. Perl will treat the true
1985 or false result of matching the pattern against $_ as the string,
1986 which is probably not what you had in mind.
1988 =item %s() called too early to check prototype
1990 (W) You've called a function that has a prototype before the parser saw a
1991 definition or declaration for it, and Perl could not check that the call
1992 conforms to the prototype. You need to either add an early prototype
1993 declaration for the subroutine in question, or move the subroutine
1994 definition ahead of the call to get proper prototype checking. Alternatively,
1995 if you are certain that you're calling the function correctly, you may put
1996 an ampersand before the name to avoid the warning. See L<perlsub>.
1998 =item %s argument is not a HASH or ARRAY element
2000 (F) The argument to exists() must be a hash or array element, such as:
2003 $ref->[12]->["susie"]
2005 =item %s argument is not a HASH or ARRAY element or slice
2007 (F) The argument to delete() must be either a hash or array element, such as:
2010 $ref->[12]->["susie"]
2012 or a hash or array slice, such as:
2014 @foo[$bar, $baz, $xyzzy]
2015 @{$ref->[12]}{"susie", "queue"}
2017 =item %s argument is not a subroutine name
2019 (F) The argument to exists() for C<exists &sub> must be a subroutine
2020 name, and not a subroutine call. C<exists &sub()> will generate this error.
2022 =item %s package attribute may clash with future reserved word: %s
2024 (W) A lowercase attribute name was used that had a package-specific handler.
2025 That name might have a meaning to Perl itself some day, even though it
2026 doesn't yet. Perhaps you should use a mixed-case attribute name, instead.
2029 =item (in cleanup) %s
2031 (W) This prefix usually indicates that a DESTROY() method raised
2032 the indicated exception. Since destructors are usually called by
2033 the system at arbitrary points during execution, and often a vast
2034 number of times, the warning is issued only once for any number
2035 of failures that would otherwise result in the same message being
2038 Failure of user callbacks dispatched using the C<G_KEEPERR> flag
2039 could also result in this warning. See L<perlcall/G_KEEPERR>.
2041 =item <> should be quotes
2043 (F) You wrote C<< require <file> >> when you should have written
2046 =item Attempt to join self
2048 (F) You tried to join a thread from within itself, which is an
2049 impossible task. You may be joining the wrong thread, or you may
2050 need to move the join() to some other thread.
2052 =item Bad evalled substitution pattern
2054 (F) You've used the /e switch to evaluate the replacement for a
2055 substitution, but perl found a syntax error in the code to evaluate,
2056 most likely an unexpected right brace '}'.
2058 =item Bad realloc() ignored
2060 (S) An internal routine called realloc() on something that had never been
2061 malloc()ed in the first place. Mandatory, but can be disabled by
2062 setting environment variable C<PERL_BADFREE> to 1.
2064 =item Bareword found in conditional
2066 (W) The compiler found a bareword where it expected a conditional,
2067 which often indicates that an || or && was parsed as part of the
2068 last argument of the previous construct, for example:
2072 It may also indicate a misspelled constant that has been interpreted
2075 use constant TYPO => 1;
2076 if (TYOP) { print "foo" }
2078 The C<strict> pragma is useful in avoiding such errors.
2080 =item Binary number > 0b11111111111111111111111111111111 non-portable
2082 (W) The binary number you specified is larger than 2**32-1
2083 (4294967295) and therefore non-portable between systems. See
2084 L<perlport> for more on portability concerns.
2086 =item Bit vector size > 32 non-portable
2088 (W) Using bit vector sizes larger than 32 is non-portable.
2090 =item Buffer overflow in prime_env_iter: %s
2092 (W) A warning peculiar to VMS. While Perl was preparing to iterate over
2093 %ENV, it encountered a logical name or symbol definition which was too long,
2094 so it was truncated to the string shown.
2096 =item Can't check filesystem of script "%s"
2098 (P) For some reason you can't check the filesystem of the script for nosuid.
2100 =item Can't declare class for non-scalar %s in "%s"
2102 (S) Currently, only scalar variables can declared with a specific class
2103 qualifier in a "my" or "our" declaration. The semantics may be extended
2104 for other types of variables in future.
2106 =item Can't declare %s in "%s"
2108 (F) Only scalar, array, and hash variables may be declared as "my" or
2109 "our" variables. They must have ordinary identifiers as names.
2111 =item Can't ignore signal CHLD, forcing to default
2113 (W) Perl has detected that it is being run with the SIGCHLD signal
2114 (sometimes known as SIGCLD) disabled. Since disabling this signal
2115 will interfere with proper determination of exit status of child
2116 processes, Perl has reset the signal to its default value.
2117 This situation typically indicates that the parent program under
2118 which Perl may be running (e.g. cron) is being very careless.
2120 =item Can't modify non-lvalue subroutine call
2122 (F) Subroutines meant to be used in lvalue context should be declared as
2123 such, see L<perlsub/"Lvalue subroutines">.
2125 =item Can't read CRTL environ
2127 (S) A warning peculiar to VMS. Perl tried to read an element of %ENV
2128 from the CRTL's internal environment array and discovered the array was
2129 missing. You need to figure out where your CRTL misplaced its environ
2130 or define F<PERL_ENV_TABLES> (see L<perlvms>) so that environ is not searched.
2132 =item Can't remove %s: %s, skipping file
2134 (S) You requested an inplace edit without creating a backup file. Perl
2135 was unable to remove the original file to replace it with the modified
2136 file. The file was left unmodified.
2138 =item Can't return %s from lvalue subroutine
2140 (F) Perl detected an attempt to return illegal lvalues (such
2141 as temporary or readonly values) from a subroutine used as an lvalue.
2142 This is not allowed.
2144 =item Can't weaken a nonreference
2146 (F) You attempted to weaken something that was not a reference. Only
2147 references can be weakened.
2149 =item Character class [:%s:] unknown
2151 (F) The class in the character class [: :] syntax is unknown.
2154 =item Character class syntax [%s] belongs inside character classes
2156 (W) The character class constructs [: :], [= =], and [. .] go
2157 I<inside> character classes, the [] are part of the construct,
2158 for example: /[012[:alpha:]345]/. Note that [= =] and [. .]
2159 are not currently implemented; they are simply placeholders for
2162 =item Constant is not %s reference
2164 (F) A constant value (perhaps declared using the C<use constant> pragma)
2165 is being dereferenced, but it amounts to the wrong type of reference. The
2166 message indicates the type of reference that was expected. This usually
2167 indicates a syntax error in dereferencing the constant value.
2168 See L<perlsub/"Constant Functions"> and L<constant>.
2170 =item constant(%s): %%^H is not localized
2172 (F) When setting compile-time-lexicalized hash %^H one should set the
2173 corresponding bit of $^H as well.
2175 =item constant(%s): %s
2177 (F) Compile-time-substitutions (such as overloaded constants and
2178 character names) were not correctly set up.
2180 =item defined(@array) is deprecated
2182 (D) defined() is not usually useful on arrays because it checks for an
2183 undefined I<scalar> value. If you want to see if the array is empty,
2184 just use C<if (@array) { # not empty }> for example.
2186 =item defined(%hash) is deprecated
2188 (D) defined() is not usually useful on hashes because it checks for an
2189 undefined I<scalar> value. If you want to see if the hash is empty,
2190 just use C<if (%hash) { # not empty }> for example.
2192 =item Did not produce a valid header
2196 =item Did you mean "local" instead of "our"?
2198 (W) Remember that "our" does not localize the declared global variable.
2199 You have declared it again in the same lexical scope, which seems superfluous.
2201 =item Document contains no data
2205 =item entering effective %s failed
2207 (F) While under the C<use filetest> pragma, switching the real and
2208 effective uids or gids failed.
2210 =item false [] range "%s" in regexp
2212 (W) A character class range must start and end at a literal character, not
2213 another character class like C<\d> or C<[:alpha:]>. The "-" in your false
2214 range is interpreted as a literal "-". Consider quoting the "-", "\-".
2217 =item Filehandle %s opened only for output
2219 (W) You tried to read from a filehandle opened only for writing. If you
2220 intended it to be a read/write filehandle, you needed to open it with
2221 "+<" or "+>" or "+>>" instead of with "<" or nothing. If
2222 you intended only to read from the file, use "<". See
2225 =item flock() on closed filehandle %s
2227 (W) The filehandle you're attempting to flock() got itself closed some
2228 time before now. Check your logic flow. flock() operates on filehandles.
2229 Are you attempting to call flock() on a dirhandle by the same name?
2231 =item Global symbol "%s" requires explicit package name
2233 (F) You've said "use strict vars", which indicates that all variables
2234 must either be lexically scoped (using "my"), declared beforehand using
2235 "our", or explicitly qualified to say which package the global variable
2238 =item Hexadecimal number > 0xffffffff non-portable
2240 (W) The hexadecimal number you specified is larger than 2**32-1
2241 (4294967295) and therefore non-portable between systems. See
2242 L<perlport> for more on portability concerns.
2244 =item Ill-formed CRTL environ value "%s"
2246 (W) A warning peculiar to VMS. Perl tried to read the CRTL's internal
2247 environ array, and encountered an element without the C<=> delimiter
2248 used to spearate keys from values. The element is ignored.
2250 =item Ill-formed message in prime_env_iter: |%s|
2252 (W) A warning peculiar to VMS. Perl tried to read a logical name
2253 or CLI symbol definition when preparing to iterate over %ENV, and
2254 didn't see the expected delimiter between key and value, so the
2257 =item Illegal binary digit %s
2259 (F) You used a digit other than 0 or 1 in a binary number.
2261 =item Illegal binary digit %s ignored
2263 (W) You may have tried to use a digit other than 0 or 1 in a binary number.
2264 Interpretation of the binary number stopped before the offending digit.
2266 =item Illegal number of bits in vec
2268 (F) The number of bits in vec() (the third argument) must be a power of
2269 two from 1 to 32 (or 64, if your platform supports that).
2271 =item Integer overflow in %s number
2273 (W) The hexadecimal, octal or binary number you have specified either
2274 as a literal or as an argument to hex() or oct() is too big for your
2275 architecture, and has been converted to a floating point number. On a
2276 32-bit architecture the largest hexadecimal, octal or binary number
2277 representable without overflow is 0xFFFFFFFF, 037777777777, or
2278 0b11111111111111111111111111111111 respectively. Note that Perl
2279 transparently promotes all numbers to a floating point representation
2280 internally--subject to loss of precision errors in subsequent
2283 =item Invalid %s attribute: %s
2285 The indicated attribute for a subroutine or variable was not recognized
2286 by Perl or by a user-supplied handler. See L<attributes>.
2288 =item Invalid %s attributes: %s
2290 The indicated attributes for a subroutine or variable were not recognized
2291 by Perl or by a user-supplied handler. See L<attributes>.
2293 =item invalid [] range "%s" in regexp
2295 The offending range is now explicitly displayed.
2297 =item Invalid separator character %s in attribute list
2299 (F) Something other than a colon or whitespace was seen between the
2300 elements of an attribute list. If the previous attribute
2301 had a parenthesised parameter list, perhaps that list was terminated
2302 too soon. See L<attributes>.
2304 =item Invalid separator character %s in subroutine attribute list
2306 (F) Something other than a colon or whitespace was seen between the
2307 elements of a subroutine attribute list. If the previous attribute
2308 had a parenthesised parameter list, perhaps that list was terminated
2311 =item leaving effective %s failed
2313 (F) While under the C<use filetest> pragma, switching the real and
2314 effective uids or gids failed.
2316 =item Lvalue subs returning %s not implemented yet
2318 (F) Due to limitations in the current implementation, array and hash
2319 values cannot be returned in subroutines used in lvalue context.
2320 See L<perlsub/"Lvalue subroutines">.
2322 =item Method %s not permitted
2326 =item Missing %sbrace%s on \N{}
2328 (F) Wrong syntax of character name literal C<\N{charname}> within
2329 double-quotish context.
2331 =item Missing command in piped open
2333 (W) You used the C<open(FH, "| command")> or C<open(FH, "command |")>
2334 construction, but the command was missing or blank.
2336 =item Missing name in "my sub"
2338 (F) The reserved syntax for lexically scoped subroutines requires that they
2339 have a name with which they can be found.
2341 =item No %s specified for -%c
2343 (F) The indicated command line switch needs a mandatory argument, but
2344 you haven't specified one.
2346 =item No package name allowed for variable %s in "our"
2348 (F) Fully qualified variable names are not allowed in "our" declarations,
2349 because that doesn't make much sense under existing semantics. Such
2350 syntax is reserved for future extensions.
2352 =item No space allowed after -%c
2354 (F) The argument to the indicated command line switch must follow immediately
2355 after the switch, without intervening spaces.
2357 =item no UTC offset information; assuming local time is UTC
2359 (S) A warning peculiar to VMS. Perl was unable to find the local
2360 timezone offset, so it's assuming that local system time is equivalent
2361 to UTC. If it's not, define the logical name F<SYS$TIMEZONE_DIFFERENTIAL>
2362 to translate to the number of seconds which need to be added to UTC to
2365 =item Octal number > 037777777777 non-portable
2367 (W) The octal number you specified is larger than 2**32-1 (4294967295)
2368 and therefore non-portable between systems. See L<perlport> for more
2369 on portability concerns.
2371 See also L<perlport> for writing portable code.
2373 =item panic: del_backref
2375 (P) Failed an internal consistency check while trying to reset a weak
2378 =item panic: kid popen errno read
2380 (F) forked child returned an incomprehensible message about its errno.
2382 =item panic: magic_killbackrefs
2384 (P) Failed an internal consistency check while trying to reset all weak
2385 references to an object.
2387 =item Parentheses missing around "%s" list
2389 (W) You said something like
2395 my ($foo, $bar) = @_;
2397 Remember that "my", "our", and "local" bind tighter than comma.
2399 =item Possible Y2K bug: %s
2401 (W) You are concatenating the number 19 with another number, which
2402 could be a potential Year 2000 problem.
2404 =item Premature end of script headers
2408 =item Repeat count in pack overflows
2410 (F) You can't specify a repeat count so large that it overflows
2411 your signed integers. See L<perlfunc/pack>.
2413 =item Repeat count in unpack overflows
2415 (F) You can't specify a repeat count so large that it overflows
2416 your signed integers. See L<perlfunc/unpack>.
2418 =item realloc() of freed memory ignored
2420 (S) An internal routine called realloc() on something that had already
2423 =item Reference is already weak
2425 (W) You have attempted to weaken a reference that is already weak.
2426 Doing so has no effect.
2428 =item setpgrp can't take arguments
2430 (F) Your system has the setpgrp() from BSD 4.2, which takes no arguments,
2431 unlike POSIX setpgid(), which takes a process ID and process group ID.
2433 =item Strange *+?{} on zero-length expression
2435 (W) You applied a regular expression quantifier in a place where it
2436 makes no sense, such as on a zero-width assertion.
2437 Try putting the quantifier inside the assertion instead. For example,
2438 the way to match "abc" provided that it is followed by three
2439 repetitions of "xyz" is C</abc(?=(?:xyz){3})/>, not C</abc(?=xyz){3}/>.
2441 =item switching effective %s is not implemented
2443 (F) While under the C<use filetest> pragma, we cannot switch the
2444 real and effective uids or gids.
2446 =item This Perl can't reset CRTL environ elements (%s)
2448 =item This Perl can't set CRTL environ elements (%s=%s)
2450 (W) Warnings peculiar to VMS. You tried to change or delete an element
2451 of the CRTL's internal environ array, but your copy of Perl wasn't
2452 built with a CRTL that contained the setenv() function. You'll need to
2453 rebuild Perl with a CRTL that does, or redefine F<PERL_ENV_TABLES> (see
2454 L<perlvms>) so that the environ array isn't the target of the change to
2455 %ENV which produced the warning.
2457 =item Unknown open() mode '%s'
2459 (F) The second argument of 3-argument open() is not among the list
2460 of valid modes: C<< < >>, C<< > >>, C<<< >> >>>, C<< +< >>,
2461 C<< +> >>, C<<< +>> >>>, C<-|>, C<|->.
2463 =item Unknown process %x sent message to prime_env_iter: %s
2465 (P) An error peculiar to VMS. Perl was reading values for %ENV before
2466 iterating over it, and someone else stuck a message in the stream of
2467 data Perl expected. Someone's very confused, or perhaps trying to
2468 subvert Perl's population of %ENV for nefarious purposes.
2470 =item Unrecognized escape \\%c passed through
2472 (W) You used a backslash-character combination which is not recognized
2473 by Perl. The character was understood literally.
2475 =item Unterminated attribute parameter in attribute list
2477 (F) The lexer saw an opening (left) parenthesis character while parsing an
2478 attribute list, but the matching closing (right) parenthesis
2479 character was not found. You may need to add (or remove) a backslash
2480 character to get your parentheses to balance. See L<attributes>.
2482 =item Unterminated attribute list
2484 (F) The lexer found something other than a simple identifier at the start
2485 of an attribute, and it wasn't a semicolon or the start of a
2486 block. Perhaps you terminated the parameter list of the previous attribute
2487 too soon. See L<attributes>.
2489 =item Unterminated attribute parameter in subroutine attribute list
2491 (F) The lexer saw an opening (left) parenthesis character while parsing a
2492 subroutine attribute list, but the matching closing (right) parenthesis
2493 character was not found. You may need to add (or remove) a backslash
2494 character to get your parentheses to balance.
2496 =item Unterminated subroutine attribute list
2498 (F) The lexer found something other than a simple identifier at the start
2499 of a subroutine attribute, and it wasn't a semicolon or the start of a
2500 block. Perhaps you terminated the parameter list of the previous attribute
2503 =item Value of CLI symbol "%s" too long
2505 (W) A warning peculiar to VMS. Perl tried to read the value of an %ENV
2506 element from a CLI symbol table, and found a resultant string longer
2507 than 1024 characters. The return value has been truncated to 1024
2510 =item Version number must be a constant number
2512 (P) The attempt to translate a C<use Module n.n LIST> statement into
2513 its equivalent C<BEGIN> block found an internal inconsistency with
2518 =head1 Obsolete Diagnostics
2522 =item Character class syntax [: :] is reserved for future extensions
2524 (W) Within regular expression character classes ([]) the syntax beginning
2525 with "[:" and ending with ":]" is reserved for future extensions.
2526 If you need to represent those character sequences inside a regular
2527 expression character class, just quote the square brackets with the
2528 backslash: "\[:" and ":\]".
2530 =item Ill-formed logical name |%s| in prime_env_iter
2532 (W) A warning peculiar to VMS. A logical name was encountered when preparing
2533 to iterate over %ENV which violates the syntactic rules governing logical
2534 names. Because it cannot be translated normally, it is skipped, and will not
2535 appear in %ENV. This may be a benign occurrence, as some software packages
2536 might directly modify logical name tables and introduce nonstandard names,
2537 or it may indicate that a logical name table has been corrupted.
2539 =item Probable precedence problem on %s
2541 (W) The compiler found a bareword where it expected a conditional,
2542 which often indicates that an || or && was parsed as part of the
2543 last argument of the previous construct, for example:
2547 =item regexp too big
2549 (F) The current implementation of regular expressions uses shorts as
2550 address offsets within a string. Unfortunately this means that if
2551 the regular expression compiles to longer than 32767, it'll blow up.
2552 Usually when you want a regular expression this big, there is a better
2553 way to do it with multiple statements. See L<perlre>.
2555 =item Use of "$$<digit>" to mean "${$}<digit>" is deprecated
2557 (D) Perl versions before 5.004 misinterpreted any type marker followed
2558 by "$" and a digit. For example, "$$0" was incorrectly taken to mean
2559 "${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004.
2561 However, the developers of Perl 5.004 could not fix this bug completely,
2562 because at least two widely-used modules depend on the old meaning of
2563 "$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the
2564 old (broken) way inside strings; but it generates this message as a
2565 warning. And in Perl 5.005, this special treatment will cease.
2571 If you find what you think is a bug, you might check the
2572 articles recently posted to the comp.lang.perl.misc newsgroup.
2573 There may also be information at http://www.perl.com/perl/, the Perl
2576 If you believe you have an unreported bug, please run the B<perlbug>
2577 program included with your release. Make sure to trim your bug down
2578 to a tiny but sufficient test case. Your bug report, along with the
2579 output of C<perl -V>, will be sent off to perlbug@perl.com to be
2580 analysed by the Perl porting team.
2584 The F<Changes> file for exhaustive details on what changed.
2586 The F<INSTALL> file for how to build Perl.
2588 The F<README> file for general stuff.
2590 The F<Artistic> and F<Copying> files for copyright information.
2594 Written by Gurusamy Sarathy <F<gsar@activestate.com>>, with many
2595 contributions from The Perl Porters.
2597 Send omissions or corrections to <F<perlbug@perl.com>>.