3 perldelta - what's new for perl v5.6.0
7 This document describes differences between the 5.005 release and this one.
9 =head1 Incompatible Changes
11 =head2 Perl Source Incompatibilities
13 Beware that any new warnings that have been added or old ones
14 that have been enhanced are B<not> considered incompatible changes.
16 Since all new warnings must be explicitly requested via the C<-w>
17 switch or the C<warnings> pragma, it is ultimately the programmer's
18 responsibility to ensure that warnings are enabled judiciously.
22 =item CHECK is a new keyword
24 In addition to C<BEGIN>, C<INIT>, C<END>, C<DESTROY> and C<AUTOLOAD>,
25 subroutines named C<CHECK> are now special. These are queued up during
26 compilation and behave similar to END blocks, except they are called at
27 the end of compilation rather than at the end of execution. They cannot
30 =item Treatment of list slices of undef has changed
32 When taking a slice of a literal list (as opposed to a slice of
33 an array or hash), Perl used to return an empty list if the
34 result happened to be composed of all undef values.
36 The new behavior is to produce an empty list if (and only if)
37 the original list was empty. Consider the following example:
39 @a = (1,undef,undef,2)[2,1,2];
41 The old behavior would have resulted in @a having no elements.
42 The new behavior ensures it has three undefined elements.
44 Note in particular that the behavior of slices of the following
45 cases remains unchanged:
49 @a = (anything_returning_empty_list())[2,1,2];
55 =head2 Perl's version numbering has changed
57 Beginning with Perl version 5.6.0, the version number convention has been
58 changed to a "dotted integer" scheme that is more commonly found in open
61 Maintenance versions of v5.6.0 will be released as v5.6.1, v5.6.2 etc.
62 The next development series following v5.6.0 will be numbered v5.7.x,
63 beginning with v5.7.0, and the next major production release following
64 v5.6.0 will be v5.8.0.
66 The English module now sets $PERL_VERSION to $^V (a string value) rather
67 than C<$]> (a numeric value). (This is a potential incompatibility.
68 Send us a report via perlbug if you are affected by this.)
70 The v1.2.3 syntax is also now legal in Perl.
71 See L<Support for strings represented as a vector of ordinals> for more on that.
73 To cope with the new versioning system's use of at least three significant
74 digits for each version component, the method used for incrementing the
75 subversion number has also changed slightly. We assume that versions older
76 than v5.6.0 have been incrementing the subversion component in multiples of
77 10. Versions after v5.6.0 will increment them by 1. Thus, using the new
78 notation, 5.005_03 is the "same" as v5.5.30, and the first maintenance
79 version following v5.6.0 will be v5.6.1 (which should be read as being
80 equivalent to a floating point value of 5.006_001 in the older format,
83 =item Literals of the form C<1.2.3> parse differently
85 Previously, numeric literals with more than one dot in them were
86 interpreted as a floating point number concatenated with one or more
87 numbers. Such "numbers" are now parsed as strings composed of the
90 For example, C<print 97.98.99> used to output C<97.9899> in earlier
91 versions, but now prints C<abc>.
93 See L<Support for strings represented as a vector of ordinals> below.
95 =item Possibly changed pseudo-random number generator
97 In 5.005_0x and earlier, perl's rand() function used the C library
98 rand(3) function. As of 5.005_52, Configure tests for drand48(),
99 random(), and rand() (in that order) and picks the first one it finds.
100 Perl programs that depend on reproducing a specific set of pseudo-random
101 numbers will now likely produce different output. You can use
102 C<sh Configure -Drandfunc=rand> to obtain the old behavior.
104 =item Hashing function for hash keys has changed
106 Perl hashes are not order preserving. The apparently random order
107 encountered when iterating on the contents of a hash is determined
108 by the hashing algorithm used. To improve the distribution of lower
109 bits in the hashed value, the algorithm has changed slightly as of
110 5.005_52. When iterating over hashes, this may yield a random order
111 that is B<different> from that of previous versions.
113 =item C<undef> fails on read only values
115 Using the C<undef> operator on a readonly value (such as $1) has
116 the same effect as assigning C<undef> to the readonly value--it
119 =item Close-on-exec bit may be set on pipe and socket handles
121 On systems that support a close-on-exec flag on filehandles, the
122 flag will be set for any handles created by pipe(), socketpair(),
123 socket(), and accept(), if that is warranted by the value of $^F
124 that may be in effect. Earlier versions neglected to set the flag
125 for handles created with these operators. See L<perlfunc/pipe>,
126 L<perlfunc/socketpair>, L<perlfunc/socket>, L<perlfunc/accept>,
129 =item Writing C<"$$1"> to mean C<"${$}1"> is unsupported
131 Perl 5.004 deprecated the interpretation of C<$$1> and
132 similar within interpolated strings to mean C<$$ . "1">,
133 but still allowed it.
135 In Perl 5.6.0 and later, C<"$$1"> always means C<"${$1}">.
137 =item delete(), values() and C<\(%h)> operate on aliases to values, not copies
139 delete(), each(), values() and hashes in a list context return the actual
140 values in the hash, instead of copies (as they used to in earlier
141 versions). Typical idioms for using these constructs copy the
142 returned values, but this can make a significant difference when
143 creating references to the returned values.
145 Keys in the hash are still returned as copies when iterating on
148 =item vec(EXPR,OFFSET,BITS) enforces powers-of-two BITS
150 vec() generates a run-time error if the BITS argument is not
151 a valid power-of-two integer.
153 =item Text of some diagnostic output has changed
155 Most references to internal Perl operations in diagnostics
156 have been changed to be more descriptive. This may be an
157 issue for programs that may incorrectly rely on the exact
158 text of diagnostics for proper functioning.
160 =item C<%@> has been removed
162 The undocumented special variable C<%@> that used to accumulate
163 "background" errors (such as those that happen in DESTROY())
164 has been removed, because it could potentially result in memory
167 =item Parenthesized not() behaves like a list operator
169 The C<not> operator now falls under the "if it looks like a function,
170 it behaves like a function" rule.
172 As a result, the parenthesized form can be used with C<grep> and C<map>.
173 The following construct used to be a syntax error before, but it works
176 grep not($_), @things;
178 On the other hand, using C<not> with a literal list slice may not
179 work. The following previously allowed construct:
181 print not (1,2,3)[0];
183 needs to be written with additional parentheses now:
185 print not((1,2,3)[0]);
187 The behavior remains unaffected when C<not> is not followed by parentheses.
189 =item Semantics of bareword prototype C<(*)> have changed
191 Arguments prototyped as C<*> will now be visible within the subroutine
192 as either a simple scalar or as a reference to a typeglob. Perl 5.005
193 always coerced simple scalar arguments to a typeglob, which wasn't useful
194 in situations where the subroutine must distinguish between a simple
195 scalar and a typeglob. See L<perlsub/Prototypes>.
197 =head2 On 64-bit platforms the semantics of bit operators have changed
199 If your platform is either natively 64-bit or your Perl has been
200 configured to used 64-bit integers, i.e., $Config{ivsize} is 8,
201 be warned that the semantics of all the bitwise numeric operators
202 (& | ^ ~ << >>) have been changed. These operators used to strictly
203 operate on the lower 32 bits of integers, but now operate over the
204 entire width of native integers. In particular, note that unary C<~>
205 will produce different results on platforms that have different
206 $Config{ivsize}. For portability, be sure to mask off the excess bits
207 in the result of unary C<~>, e.g., C<~$x & 0xffffffff>.
209 =head2 The shell returned by the getpwxxx() is now tainted
211 Because the user can affect her own login shell the shell returned
212 by the getpwent(), getpwnam(), and getpwuid() functions is tainted.
216 =head2 C Source Incompatibilities
220 =item C<PERL_POLLUTE>
222 Release 5.005 grandfathered old global symbol names by providing preprocessor
223 macros for extension source compatibility. As of release 5.6.0, these
224 preprocessor definitions are not available by default. You need to explicitly
225 compile perl with C<-DPERL_POLLUTE> to get these definitions. For
226 extensions still using the old symbols, this option can be
227 specified via MakeMaker:
229 perl Makefile.PL POLLUTE=1
231 =item C<PERL_IMPLICIT_CONTEXT>
233 NOTE: PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
234 with one of -Dusethreads, -Dusemultiplicity, or both. It is not
235 intended to be enabled by users at this time.
237 This new build option provides a set of macros for all API functions
238 such that an implicit interpreter/thread context argument is passed to
239 every API function. As a result of this, something like C<sv_setsv(foo,bar)>
240 amounts to a macro invocation that actually translates to something like
241 C<Perl_sv_setsv(my_perl,foo,bar)>. While this is generally expected
242 to not have any significant source compatibility issues, the difference
243 between a macro and a real function call will need to be considered.
245 This means that there B<is> a source compatibility issue as a result of
246 this if your extensions attempt to use pointers to any of the Perl API
249 Note that the above issue is not relevant to the default build of
250 Perl, whose interfaces continue to match those of prior versions
251 (but subject to the other options described here).
253 See L<perlguts/"The Perl API"> for detailed information on the
254 ramifications of building Perl with this option.
256 =item C<PERL_POLLUTE_MALLOC>
258 Enabling Perl's malloc in release 5.005 and earlier caused the namespace of
259 the system's malloc family of functions to be usurped by the Perl versions,
260 since by default they used the same names. Besides causing problems on
261 platforms that do not allow these functions to be cleanly replaced, this
262 also meant that the system versions could not be called in programs that
263 used Perl's malloc. Previous versions of Perl have allowed this behaviour
264 to be suppressed with the HIDEMYMALLOC and EMBEDMYMALLOC preprocessor
267 As of release 5.6.0, Perl's malloc family of functions have default names
268 distinct from the system versions. You need to explicitly compile perl with
269 C<-DPERL_POLLUTE_MALLOC> to get the older behaviour. HIDEMYMALLOC
270 and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now
273 Note that these functions do B<not> constitute Perl's memory allocation API.
274 See L<perlguts/"Memory Allocation"> for further information about that.
278 =head2 Compatible C Source API Changes
282 =item C<PATCHLEVEL> is now C<PERL_VERSION>
284 The cpp macros C<PERL_REVISION>, C<PERL_VERSION>, and C<PERL_SUBVERSION>
285 are now available by default from perl.h, and reflect the base revision,
286 patchlevel, and subversion respectively. C<PERL_REVISION> had no
287 prior equivalent, while C<PERL_VERSION> and C<PERL_SUBVERSION> were
288 previously available as C<PATCHLEVEL> and C<SUBVERSION>.
290 The new names cause less pollution of the B<cpp> namespace and reflect what
291 the numbers have come to stand for in common practice. For compatibility,
292 the old names are still supported when F<patchlevel.h> is explicitly
293 included (as required before), so there is no source incompatibility
298 =head2 Binary Incompatibilities
300 In general, the default build of this release is expected to be binary
301 compatible for extensions built with the 5.005 release or its maintenance
302 versions. However, specific platforms may have broken binary compatibility
303 due to changes in the defaults used in hints files. Therefore, please be
304 sure to always check the platform-specific README files for any notes to
307 The usethreads or usemultiplicity builds are B<not> binary compatible
308 with the corresponding builds in 5.005.
310 On platforms that require an explicit list of exports (AIX, OS/2 and Windows,
311 among others), purely internal symbols such as parser functions and the
312 run time opcodes are not exported by default. Perl 5.005 used to export
313 all functions irrespective of whether they were considered part of the
316 For the full list of public API functions, see L<perlapi>.
318 =head1 Installation and Configuration Improvements
320 =head2 -Dusethreads means something different
322 WARNING: Support for threads continues to be an experimental feature.
323 Interfaces and implementation are subject to sudden and drastic changes.
325 The -Dusethreads flag now enables the experimental interpreter-based thread
326 support by default. To get the flavor of experimental threads that was in
327 5.005 instead, you need to run Configure with "-Dusethreads -Duse5005threads".
329 As of v5.6.0, interpreter-threads support is still lacking a way to
330 create new threads from Perl (i.e., C<use Thread;> will not work with
331 interpreter threads). C<use Thread;> continues to be available when you
332 specify the -Duse5005threads option to Configure, bugs and all.
334 =head2 New Configure flags
336 The following new flags may be enabled on the Configure command line
337 by running Configure with C<-Dflag>.
340 usethreads useithreads (new interpreter threads: no Perl API yet)
341 usethreads use5005threads (threads as they were in 5.005)
343 use64bitint (equal to now deprecated 'use64bits')
349 usesocks (only SOCKS v5 supported)
351 =head2 Threadedness and 64-bitness now more daring
353 The Configure options enabling the use of threads and the use of
354 64-bitness are now more daring in the sense that they no more have an
355 explicit list of operating systems of known threads/64-bit
356 capabilities. In other words: if your operating system has the
357 necessary APIs and datatypes, you should be able just to go ahead and
358 use them, for threads by Configure -Dusethreads, and for 64 bits
359 either explicitly by Configure -Duse64bitint or implicitly if your
360 system has 64-bit wide datatypes. See also L<"64-bit support">.
364 Some platforms have "long doubles", floating point numbers of even
365 larger range than ordinary "doubles". To enable using long doubles for
366 Perl's scalars, use -Duselongdouble.
370 You can enable both -Duse64bitint and -Duselongdouble with -Dusemorebits.
371 See also L<"64-bit support">.
373 =head2 -Duselargefiles
375 Some platforms support system APIs that are capable of handling large files
376 (typically, files larger than two gigabytes). Perl will try to use these
377 APIs if you ask for -Duselargefiles.
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 proxy protocol library (v5, not v4). For more information
394 http://www.socks.nec.com/
398 You can "post-edit" the Configure variables using the Configure C<-A>
399 switch. The editing happens immediately after the platform specific
400 hints files have been processed but before the actual configuration
401 process starts. Run C<Configure -h> to find out the full C<-A> syntax.
403 =head2 Enhanced Installation Directories
405 The installation structure has been enriched to improve the support
406 for maintaining multiple versions of perl, to provide locations for
407 vendor-supplied modules, scripts, and manpages, and to ease maintenance
408 of locally-added modules, scripts, and manpages. See the section on
409 Installation Directories in the INSTALL file for complete details.
410 For most users building and installing from source, the defaults should
413 If you previously used C<Configure -Dsitelib> or C<-Dsitearch> to set
414 special values for library directories, you might wish to consider using
415 the new C<-Dsiteprefix> setting instead. Also, if you wish to re-use a
416 config.sh file from an earlier version of perl, you should be sure to
417 check that Configure makes sensible choices for the new directories.
418 See INSTALL for complete details.
422 =head2 Unicode and UTF-8 support
424 WARNING: This is an experimental feature. Implementation details are
427 Perl now uses 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. Implementation details are
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 macro USE_ITHREADS by default, which in turn
463 enables Perl source code changes that provide a clear separation between
464 the op tree and the data it operates with. The former is immutable, and
465 can therefore be shared between an interpreter and all of its clones,
466 while the latter is considered local to each interpreter, and is therefore
467 copied for each clone.
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 =head2 Lexically scoped warning categories
477 You can now control the granularity of warnings emitted by perl at a finer
478 level using the C<use warnings> pragma. See L<warnings> and L<perllexwarn>
481 =head2 Lvalue subroutines
483 WARNING: This is an experimental feature. Details are subject to change.
485 Subroutines can now return modifiable lvalues.
486 See L<perlsub/"Lvalue subroutines">.
488 =head2 "our" declarations
490 An "our" declaration introduces a value that can be best understood
491 as a lexically scoped symbolic alias to a global variable in the
492 package that was current where the variable was declared. This is
493 mostly useful as an alternative to the C<vars> pragma, but also provides
494 the opportunity to introduce typing and other attributes for such
495 variables. See L<perlfunc/our>.
497 =head2 Support for strings represented as a vector of ordinals
499 Literals of the form C<v1.2.3.4> are now parsed as a string composed of
500 of characters with the specified ordinals. This is an alternative, more
501 readable way to construct (possibly unicode) strings instead of
502 interpolating characters, as in C<"\x{1}\x{2}\x{3}\x{4}">. The leading
503 C<v> may be omitted if there are more than two ordinals, so C<1.2.3> is
504 parsed the same as C<v1.2.3>.
506 Strings written in this form are also useful to represent version "numbers".
507 It is easy to compare such version "numbers" (which are really just plain
508 strings) using any of the usual string comparison operators C<eq>, C<ne>,
509 C<lt>, C<gt>, etc., or perform bitwise string operations on them using C<|>,
512 In conjunction with the new C<$^V> magic variable (which contains
513 the perl version as a string), such literals can be used as a readable way
514 to check if you're running a particular version of Perl:
516 # this will parse in older versions of Perl also
517 if ($^V and $^V gt v5.6.0) {
518 # new features supported
521 C<require> and C<use> also have some special magic to support such literals.
522 They will be interpreted as a version rather than as a module name:
524 require v5.6.0; # croak if $^V lt v5.6.0
525 use v5.6.0; # same, but croaks at compile-time
527 Alternatively, the C<v> may be omitted if there is more than one dot:
532 Also, C<sprintf> and C<printf> support the Perl-specific format flag C<%v>
533 to print ordinals of characters in arbitrary strings:
535 printf "v%vd", $^V; # prints current version, such as "v5.5.650"
536 printf "%*vX", ":", $addr; # formats IPv6 address
537 printf "%*vb", " ", $bits; # displays bitstring
539 See L<perldata/"Scalar value constructors"> for additional information.
541 =head2 Weak references
543 WARNING: This is an experimental feature. Details are subject to change.
545 In previous versions of Perl, you couldn't cache objects so as
546 to allow them to be deleted if the last reference from outside
547 the cache is deleted. The reference in the cache would hold a
548 reference count on the object and the objects would never be
551 Another familiar problem is with circular references. When an
552 object references itself, its reference count would never go
553 down to zero, and it would not get destroyed until the program
556 Weak references solve this by allowing you to "weaken" any
557 reference, that is, make it not count towards the reference count.
558 When the last non-weak reference to an object is deleted, the object
559 is destroyed and all the weak references to the object are
560 automatically undef-ed.
562 To use this feature, you need the WeakRef package from CPAN, which
563 contains additional documentation.
565 =head2 File globbing implemented internally
567 WARNING: This is currently an experimental feature. Interfaces and
568 implementation are likely to change.
570 Perl now uses the File::Glob implementation of the glob() operator
571 automatically. This avoids using an external csh process and the
572 problems associated with it.
574 =head2 Binary numbers supported
576 Binary numbers are now supported as literals, in s?printf formats, and
580 printf "The answer is: %b\n", oct("0b101010");
582 =head2 Some arrows may be omitted in calls through references
584 Perl now allows the arrow to be omitted in many constructs
585 involving subroutine calls through references. For example,
586 C<< $foo[10]->('foo') >> may now be written C<$foo[10]('foo')>.
587 This is rather similar to how the arrow may be omitted from
588 C<< $foo[10]->{'foo'} >>. Note however, that the arrow is still
589 required for C<< foo(10)->('bar') >>.
591 =head2 exists() is supported on subroutine names
593 The exists() builtin now works on subroutine names. A subroutine
594 is considered to exist if it has been declared (even if implicitly).
595 See L<perlfunc/exists> for examples.
597 =head2 exists() and delete() are supported on array elements
599 The exists() and delete() builtins now work on simple arrays as well.
600 The behavior is similar to that on hash elements.
602 exists() can be used to check whether an array element has been
603 initialized. This avoids autovivifying array elements that don't exist.
604 If the array is tied, the EXISTS() method in the corresponding tied
605 package will be invoked.
607 delete() may be used to remove an element from the array and return
608 it. The array element at that position returns to its unintialized
609 state, so that testing for the same element with exists() will return
610 false. If the element happens to be the one at the end, the size of
611 the array also shrinks up to the highest element that tests true for
612 exists(), or 0 if none such is found. If the array is tied, the DELETE()
613 method in the corresponding tied package will be invoked.
615 See L<perlfunc/exists> and L<perlfunc/delete> for examples.
617 =head2 syswrite() ease-of-use
619 The length argument of C<syswrite()> has become optional.
621 =head2 File and directory handles can be autovivified
623 Similar to how constructs such as C<< $x->[0] >> autovivify a reference,
624 handle constructors (open(), opendir(), pipe(), socketpair(), sysopen(),
625 socket(), and accept()) now autovivify a file or directory handle
626 if the handle passed to them is an uninitialized scalar variable. This
627 allows the constructs such as C<open(my $fh, ...)> and C<open(local $fh,...)>
628 to be used to create filehandles that will conveniently be closed
629 automatically when the scope ends, provided there are no other references
630 to them. This largely eliminates the need for typeglobs when opening
631 filehandles that must be passed around, as in the following example:
635 or die "Can't open '@_': $!";
640 my $f = myopen("</etc/motd");
642 # $f implicitly closed here
645 =head2 open() with more than two arguments
647 If open() is passed three arguments instead of two, the second arguments
648 is used as the mode and the third argument is taken to be the file name.
649 This is primarily useful for protecting against unintended magic behavior
650 of the traditional two-argument form. See L<perlfunc/open>.
652 =head2 64-bit support
654 NOTE: The Configure flags -Duselonglong and -Duse64bits have been
655 deprecated. Use -Duse64bitint instead.
657 Any platform that has 64-bit integers either
659 (1) natively as longs or ints
660 (2) via special compiler flags
661 (3) using long long or int64_t
663 are able to use "quads" (64-bit integers) as follows:
669 constants (decimal, hexadecimal, octal, binary) in the code
673 arguments to oct() and hex()
677 arguments to print(), printf() and sprintf() (flag prefixes ll, L, q)
685 pack() and unpack() "q" and "Q" formats
689 in basic arithmetics: + - * / % (NOTE: operating close to the limits
690 of the integer values may produce surprising results)
694 in bit arithmetics: & | ^ ~ << >> (NOTE: these used to be forced
695 to be 32 bits wide but now operate on the full native width.)
703 Note that unless you have the case (a) you will have to configure
704 and compile Perl using the -Duse64bitint Configure flag.
706 There are actually two modes of 64-bitness: the first one is achieved
707 using Configure -Duse64bitint and the second one using Configure
708 -Duse64bitall. The difference is that the first one is minimal and
709 the second one maximal.
711 The C<use64bitint> does only as much as is required to get 64-bit
712 integers into Perl (this may mean, for example, using "long longs")
713 while your memory may still be limited to 2 gigabytes (because your
714 pointers could still be 32-bit). Note that the name C<64bitint> does
715 not imply that your C compiler will be using 64-bit C<int>s (it might,
716 but it doesn't have to): the C<use64bitint> means that you will be
717 able to have 64 bits wide scalar values.
719 The C<use64bitall> goes all the way by attempting to switch also
720 integers (if it can), longs (and pointers) to being 64-bit. This may
721 create an even more binary incompatible Perl than -Duse64bitint: the
722 resulting executable may not run at all in a 32-bit box, or you may
723 have to reboot/reconfigure/rebuild your operating system to be 64-bit
726 Natively 64-bit systems like Alpha and Cray need neither -Duse64bitint
729 Last but not least: note that due to Perl's habit of always using
730 floating point numbers, the quads are still not true integers.
731 When quads overflow their limits (0...18_446_744_073_709_551_615 unsigned,
732 -9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they
733 are silently promoted to floating point numbers, after which they will
734 start losing precision (in their lower digits).
736 =head2 Large file support
738 If you have filesystems that support "large files" (files larger than
739 2 gigabytes), you may now also be able to create and access them from
740 Perl. NOTE: the default action is to use the large file support, if
741 available on the platform.
743 If the large file support is on, and you have a Fcntl constant
744 O_LARGEFILE, the O_LARGEFILE is automatically added to the flags
747 Beware: unless your filesystem also supports "sparse files" seeking to
748 umpteen petabytes may be unadvisable.
750 Note that in addition to requiring a proper file system to do large
751 files you may also need to adjust your per-process (or your
752 per-system, or per-process-group, or per-user-group) maximum filesize
753 limits before running Perl scripts that try to handle large files,
754 especially if you intend to write such files.
756 Finally, in addition to your process/process group maximum filesize
757 limits, you may have quota limits on your filesystems that stop you
758 (your user id or your user group id) from using large files.
760 Adjusting your process/user/group/file system/operating system limits
761 is outside the scope of Perl core language. For process limits, you
762 may try increasing the limits using your shell's limits/limit/ulimit
763 command before running Perl. The BSD::Resource extension (not
764 included with the standard Perl distribution) may also be of use, it
765 offers the getrlimit/setrlimit interface that can be used to adjust
766 process resource usage limits, including the maximum filesize limit.
770 In some systems you may be able to use long doubles to enhance the
771 range and precision of your double precision floating point numbers
772 (that is, Perl's numbers). Use Configure -Duselongdouble to enable
773 this support (if it is available).
777 You can "Configure -Dusemorebits" to turn on both the 64-bit support
778 and the long double support.
780 =head2 Enhanced support for sort() subroutines
782 Perl subroutines with a prototype of C<($$)>, and XSUBs in general, can
783 now be used as sort subroutines. In either case, the two elements to
784 be compared are passed as normal parameters in @_. See L<perlfunc/sort>.
786 For unprototyped sort subroutines, the historical behavior of passing
787 the elements to be compared as the global variables $a and $b remains
790 =head2 Better syntax checks on parenthesized unary operators
794 print defined(&foo,&bar,&baz);
795 print uc("foo","bar","baz");
798 used to be accidentally allowed in earlier versions, and produced
799 unpredictable behaviour. Some produced ancillary warnings
800 when used in this way; others silently did the wrong thing.
802 The parenthesized forms of most unary operators that expect a single
803 argument now ensure that they are not called with more than one
804 argument, making the cases shown above syntax errors. The usual
807 print defined &foo, &bar, &baz;
808 print uc "foo", "bar", "baz";
811 remains unchanged. See L<perlop>.
813 =head2 POSIX character class syntax [: :] supported
815 For example to match alphabetic characters use /[[:alpha:]]/.
816 See L<perlre> for details.
818 =head2 Improved C<qw//> operator
820 The C<qw//> operator is now evaluated at compile time into a true list
821 instead of being replaced with a run time call to C<split()>. This
822 removes the confusing misbehaviour of C<qw//> in scalar context, which
823 had inherited that behaviour from split().
827 $foo = ($bar) = qw(a b c); print "$foo|$bar\n";
829 now correctly prints "3|a", instead of "2|a".
831 =head2 pack() format 'Z' supported
833 The new format type 'Z' is useful for packing and unpacking null-terminated
834 strings. See L<perlfunc/"pack">.
836 =head2 pack() format modifier '!' supported
838 The new format type modifier '!' is useful for packing and unpacking
839 native shorts, ints, and longs. See L<perlfunc/"pack">.
841 =head2 pack() and unpack() support counted strings
843 The template character '/' can be used to specify a counted string
844 type to be packed or unpacked. See L<perlfunc/"pack">.
846 =head2 Comments in pack() templates
848 The '#' character in a template introduces a comment up to
849 end of the line. This facilitates documentation of pack()
852 =head2 $^X variables may now have names longer than one character
854 Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax
855 error. Now variable names that begin with a control character may be
856 arbitrarily long. However, for compatibility reasons, these variables
857 I<must> be written with explicit braces, as C<${^XY}> for example.
858 C<${^XYZ}> is synonymous with ${"\cXYZ"}. Variable names with more
859 than one control character, such as C<${^XY^Z}>, are illegal.
861 The old syntax has not changed. As before, `^X' may be either a
862 literal control-X character or the two-character sequence `caret' plus
863 `X'. When braces are omitted, the variable name stops after the
864 control character. Thus C<"$^XYZ"> continues to be synonymous with
865 C<$^X . "YZ"> as before.
867 As before, lexical variables may not have names beginning with control
868 characters. As before, variables whose names begin with a control
869 character are always forced to be in package `main'. All such variables
870 are reserved for future extensions, except those that begin with
871 C<^_>, which may be used by user programs and are guaranteed not to
872 acquire special meaning in any future version of Perl.
874 =head2 C<use attrs> implicit in subroutine attributes
876 Formerly, if you wanted to mark a subroutine as being a method call or
877 as requiring an automatic lock() when it is entered, you had to declare
878 that with a C<use attrs> pragma in the body of the subroutine.
879 That can now be accomplished with declaration syntax, like this:
881 sub mymethod : locked method ;
883 sub mymethod : locked method {
887 sub othermethod :locked :method ;
889 sub othermethod :locked :method {
894 (Note how only the first C<:> is mandatory, and whitespace surrounding
895 the C<:> is optional.)
897 F<AutoSplit.pm> and F<SelfLoader.pm> have been updated to keep the attributes
898 with the stubs they provide. See L<attributes>.
900 =head2 Support for interpolating named characters
902 The new C<\N> escape interpolates named characters within strings.
903 For example, C<"Hi! \N{WHITE SMILING FACE}"> evaluates to a string
904 with a unicode smiley face at the end.
906 =head2 C<require> and C<do> may be overridden
908 C<require> and C<do 'file'> operations may be overridden locally
909 by importing subroutines of the same name into the current package
910 (or globally by importing them into the CORE::GLOBAL:: namespace).
911 Overriding C<require> will also affect C<use>, provided the override
912 is visible at compile-time.
913 See L<perlsub/"Overriding Built-in Functions">.
915 =head2 New variable $^C reflects C<-c> switch
917 C<$^C> has a boolean value that reflects whether perl is being run
918 in compile-only mode (i.e. via the C<-c> switch). Since
919 BEGIN blocks are executed under such conditions, this variable
920 enables perl code to determine whether actions that make sense
921 only during normal running are warranted. See L<perlvar>.
923 =head2 New variable $^V contains Perl version as a string
925 C<$^V> contains the Perl version number as a string composed of
926 characters whose ordinals match the version numbers, i.e. v5.6.0.
927 This may be used in string comparisons.
929 See C<Support for strings represented as a vector of ordinals> for an
932 =head2 Optional Y2K warnings
934 If Perl is built with the cpp macro C<PERL_Y2KWARN> defined,
935 it emits optional warnings when concatenating the number 19
938 This behavior must be specifically enabled when running Configure.
939 See F<INSTALL> and F<README.Y2K>.
941 =head1 Significant bug fixes
943 =head2 <HANDLE> on empty files
945 With C<$/> set to C<undef>, "slurping" an empty file returns a string of
946 zero length (instead of C<undef>, as it used to) the first time the
947 HANDLE is read after C<$/> is set to C<undef>. Further reads yield
950 This means that the following will append "foo" to an empty file (it used
953 perl -0777 -pi -e 's/^/foo/' empty_file
957 perl -pi -e 's/^/foo/' empty_file
959 is unchanged (it continues to leave the file empty).
961 =head2 C<eval '...'> improvements
963 Line numbers (as reflected by caller() and most diagnostics) within
964 C<eval '...'> were often incorrect where here documents were involved.
965 This has been corrected.
967 Lexical lookups for variables appearing in C<eval '...'> within
968 functions that were themselves called within an C<eval '...'> were
969 searching the wrong place for lexicals. The lexical search now
970 correctly ends at the subroutine's block boundary.
972 Parsing of here documents used to be flawed when they appeared as
973 the replacement expression in C<eval 's/.../.../e'>. This has
976 =head2 All compilation errors are true errors
978 Some "errors" encountered at compile time were by neccessity
979 generated as warnings followed by eventual termination of the
980 program. This enabled more such errors to be reported in a
981 single run, rather than causing a hard stop at the first error
982 that was encountered.
984 The mechanism for reporting such errors has been reimplemented
985 to queue compile-time errors and report them at the end of the
986 compilation as true errors rather than as warnings. This fixes
987 cases where error messages leaked through in the form of warnings
988 when code was compiled at run time using C<eval STRING>, and
989 also allows such errors to be reliably trapped using C<eval "...">.
991 =head2 Automatic flushing of output buffers
993 fork(), exec(), system(), qx//, and pipe open()s now flush buffers
994 of all files opened for output when the operation was attempted. This
995 mostly eliminates confusing buffering mishaps suffered by users unaware
996 of how Perl internally handles I/O.
998 This is not supported on some platforms like Solaris where a suitably
999 correct implementation of fflush(NULL) isn't available.
1001 =head2 Better diagnostics on meaningless filehandle operations
1003 Constructs such as C<< open(<FH>) >> and C<< close(<FH>) >>
1004 are compile time errors. Attempting to read from filehandles that
1005 were opened only for writing will now produce warnings (just as
1006 writing to read-only filehandles does).
1008 =head2 Where possible, buffered data discarded from duped input filehandle
1010 C<< open(NEW, "<&OLD") >> now attempts to discard any data that
1011 was previously read and buffered in C<OLD> before duping the handle.
1012 On platforms where doing this is allowed, the next read operation
1013 on C<NEW> will return the same data as the corresponding operation
1014 on C<OLD>. Formerly, it would have returned the data from the start
1015 of the following disk block instead.
1017 =head2 eof() has the same old magic as <>
1019 C<eof()> would return true if no attempt to read from C<< <> >> had
1020 yet been made. C<eof()> has been changed to have a little magic of its
1021 own, it now opens the C<< <> >> files.
1023 =head2 system(), backticks and pipe open now reflect exec() failure
1025 On Unix and similar platforms, system(), qx() and open(FOO, "cmd |")
1026 etc., are implemented via fork() and exec(). When the underlying
1027 exec() fails, earlier versions did not report the error properly,
1028 since the exec() happened to be in a different process.
1030 The child process now communicates with the parent about the
1031 error in launching the external command, which allows these
1032 constructs to return with their usual error value and set $!.
1034 =head2 Implicitly closed filehandles are safer
1036 Sometimes implicitly closed filehandles (as when they are localized,
1037 and Perl automatically closes them on exiting the scope) could
1038 inadvertently set $? or $!. This has been corrected.
1040 =head2 C<(\$)> prototype and C<$foo{a}>
1042 A scalar reference prototype now correctly allows a hash or
1043 array element in that slot.
1045 =head2 Pseudo-hashes work better
1047 Dereferencing some types of reference values in a pseudo-hash,
1048 such as C<< $ph->{foo}[1] >>, was accidentally disallowed. This has
1051 When applied to a pseudo-hash element, exists() now reports whether
1052 the specified value exists, not merely if the key is valid.
1054 delete() now works on pseudo-hashes. When given a pseudo-hash element
1055 or slice it deletes the values corresponding to the keys (but not the keys
1056 themselves). See L<perlref/"Pseudo-hashes: Using an array as a hash">.
1058 Pseudo-hash slices with constant keys are now optimized to array lookups
1061 The C<fields> pragma now provides ways to create pseudo-hashes, via
1062 fields::new() and fields::phash(). See L<fields>.
1064 =head2 C<goto &sub> and AUTOLOAD
1066 The C<goto &sub> construct works correctly when C<&sub> happens
1069 =head2 C<-bareword> allowed under C<use integer>
1071 The autoquoting of barewords preceded by C<-> did not work
1072 in prior versions when the C<integer> pragma was enabled.
1073 This has been fixed.
1075 =head2 Boolean assignment operators are legal lvalues
1077 Constructs such as C<($a ||= 2) += 1> are now allowed.
1079 =head2 C<sort $coderef @foo> allowed
1081 sort() did not accept a subroutine reference as the comparison
1082 function in earlier versions. This is now permitted.
1084 =head2 Failures in DESTROY()
1086 When code in a destructor threw an exception, it went unnoticed
1087 in earlier versions of Perl, unless someone happened to be
1088 looking in $@ just after the point the destructor happened to
1089 run. Such failures are now visible as warnings when warnings are
1092 =head2 Locale bugs fixed
1094 printf() and sprintf() previously reset the numeric locale
1095 back to the default "C" locale. This has been fixed.
1097 Numbers formatted according to the local numeric locale
1098 (such as using a decimal comma instead of a decimal dot) caused
1099 "isn't numeric" warnings, even while the operations accessing
1100 those numbers produced correct results. These warnings have been
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 Taint failures under C<-U>
1123 When running in unsafe mode, taint violations could sometimes
1124 cause silent failures. This has been fixed.
1126 =head2 END blocks and the C<-c> switch
1128 Prior versions used to run BEGIN B<and> END blocks when Perl was
1129 run in compile-only mode. Since this is typically not the expected
1130 behavior, END blocks are not executed anymore when the C<-c> switch
1133 See L<CHECK blocks> for how to run things when the compile phase ends.
1135 =head2 Potential to leak DATA filehandles
1137 Using the C<__DATA__> token creates an implicit filehandle to
1138 the file that contains the token. It is the program's
1139 responsibility to close it when it is done reading from it.
1141 This caveat is now better explained in the documentation.
1144 =head2 Diagnostics follow STDERR
1146 Diagnostic output now goes to whichever file the C<STDERR> handle
1147 is pointing at, instead of always going to the underlying C runtime
1148 library's C<stderr>.
1150 =head2 Other fixes for better diagnostics
1152 Line numbers are no longer suppressed (under most likely circumstances)
1153 during the global destruction phase.
1155 Diagnostics emitted from code running in threads other than the main
1156 thread are now accompanied by the thread ID.
1158 Embedded null characters in diagnostics now actually show up. They
1159 used to truncate the message in prior versions.
1161 $foo::a and $foo::b are now exempt from "possible typo" warnings only
1162 if sort() is encountered in package C<foo>.
1164 Unrecognized alphabetic escapes encountered when parsing quote
1165 constructs now generate a warning, since they may take on new
1166 semantics in later versions of Perl.
1168 Many diagnostics now report the internal operation in which the warning
1169 was provoked, like so:
1171 Use of uninitialized value in concatenation (.) at (eval 1) line 1.
1172 Use of uninitialized value in print at (eval 1) line 1.
1174 Diagnostics that occur within eval may also report the file and line
1175 number where the eval is located, in addition to the eval sequence
1176 number and the line number within the evaluated text itself. For
1179 Not enough arguments for scalar at (eval 4)[newlib/perl5db.pl:1411] line 2, at EOF
1181 =head1 Performance enhancements
1183 =head2 Simple sort() using { $a <=> $b } and the like are optimized
1185 Many common sort() operations using a simple inlined block are now
1186 optimized for faster performance.
1188 =head2 Optimized assignments to lexical variables
1190 Certain operations in the RHS of assignment statements have been
1191 optimized to directly set the lexical variable on the LHS,
1192 eliminating redundant copying overheads.
1194 =head2 Faster subroutine calls
1196 Minor changes in how subroutine calls are handled internally
1197 provide marginal improvements in performance.
1199 =head1 Platform specific changes
1201 =head2 Supported platforms
1207 VM/ESA is now supported.
1211 Siemens BS2000 is now supported under the POSIX Shell.
1215 The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread
1220 GNU/Hurd is now supported.
1224 Rhapsody/Darwin is now supported.
1228 EPOC is is now supported (on Psion 5).
1238 Perl now works with djgpp 2.02 (and 2.03 alpha).
1242 Environment variable names are not converted to uppercase any more.
1246 Incorrect exit codes from backticks have been fixed.
1250 This port continues to use its own builtin globbing (not File::Glob).
1254 =head2 OS390 (OpenEdition MVS)
1256 Support for this EBCDIC platform has not been renewed in this release.
1257 There are difficulties in reconciling Perl's standardization on UTF-8
1258 as its internal representation for characters with the EBCDIC character
1259 set, because the two are incompatible.
1261 It is unclear whether future versions will renew support for this
1262 platform, but the possibility exists.
1266 Numerous revisions and extensions to configuration, build, testing, and
1267 installation process to accomodate core changes and VMS-specific options.
1269 Expand %ENV-handling code to allow runtime mapping to logical names,
1270 CLI symbols, and CRTL environ array.
1272 Extension of subprocess invocation code to accept filespecs as command
1275 Add to Perl command line processing the ability to use default file types and
1276 to recognize Unix-style C<2E<gt>&1>.
1278 Expansion of File::Spec::VMS routines, and integration into ExtUtils::MM_VMS.
1280 Extension of ExtUtils::MM_VMS to handle complex extensions more flexibly.
1282 Barewords at start of Unix-syntax paths may be treated as text rather than
1283 only as logical names.
1285 Optional secure translation of several logical names used internally by Perl.
1287 Miscellaneous bugfixing and porting of new core code to VMS.
1289 Thanks are gladly extended to the many people who have contributed VMS
1290 patches, testing, and ideas.
1294 Perl can now emulate fork() internally, using multiple interpreters running
1295 in different concurrent threads. This support must be enabled at build
1296 time. See L<perlfork> for detailed information.
1298 When given a pathname that consists only of a drivename, such as C<A:>,
1299 opendir() and stat() now use the current working directory for the drive
1300 rather than the drive root.
1302 The builtin XSUB functions in the Win32:: namespace are documented. See
1305 $^X now contains the full path name of the running executable.
1307 A Win32::GetLongPathName() function is provided to complement
1308 Win32::GetFullPathName() and Win32::GetShortPathName(). See L<Win32>.
1310 POSIX::uname() is supported.
1312 system(1,...) now returns true process IDs rather than process
1313 handles. kill() accepts any real process id, rather than strictly
1314 return values from system(1,...).
1316 For better compatibility with Unix, C<kill(0, $pid)> can now be used to
1317 test whether a process exists.
1319 The C<Shell> module is supported.
1321 Better support for building Perl under command.com in Windows 95
1324 Scripts are read in binary mode by default to allow ByteLoader (and
1325 the filter mechanism in general) to work properly. For compatibility,
1326 the DATA filehandle will be set to text mode if a carriage return is
1327 detected at the end of the line containing the __END__ or __DATA__
1328 token; if not, the DATA filehandle will be left open in binary mode.
1329 Earlier versions always opened the DATA filehandle in text mode.
1331 The glob() operator is implemented via the C<File::Glob> extension,
1332 which supports glob syntax of the C shell. This increases the flexibility
1333 of the glob() operator, but there may be compatibility issues for
1334 programs that relied on the older globbing syntax. If you want to
1335 preserve compatibility with the older syntax, you might want to run
1336 perl with C<-MFile::DosGlob>. For details and compatibility information,
1345 Compatibility tests for C<sub : attrs> vs the older C<use attrs>.
1349 Tests for new environment scalar capability (e.g., C<use Env qw($BAR);>).
1353 Tests for new environment array capability (e.g., C<use Env qw(@PATH);>).
1357 IO constants (SEEK_*, _IO*).
1361 Directory-related IO methods (new, read, close, rewind, tied delete).
1363 =item lib/io_multihomed
1365 INET sockets with multi-homed hosts.
1377 Regression tests for C<my ($x,@y,%z) : attrs> and <sub : attrs>.
1381 File test operators.
1385 Verify operations that access pad objects (lexicals and temporaries).
1389 Verify C<exists &sub> operations.
1393 =head1 Modules and Pragmata
1401 While used internally by Perl as a pragma, this module also
1402 provides a way to fetch subroutine and variable attributes.
1407 WARNING: The Compiler suite remains highly experimental. The
1408 generated code may not be correct, even it manages to execute
1411 The Perl Compiler suite has been extensively reworked for this
1412 release. More of the standard Perl testsuite passes when run
1413 under the Compiler, but there is still a significant way to
1414 go to achieve production quality compiled executables.
1418 The ByteLoader is a dedicated extension to generate and run
1419 Perl bytecode. See L<ByteLoader>.
1423 References can now be used.
1425 The new version also allows a leading underscore in constant names, but
1426 disallows a double leading underscore (as in "__LINE__"). Some other names
1427 are disallowed or warned against, including BEGIN, END, etc. Some names
1428 which were forced into main:: used to fail silently in some cases; now they're
1429 fatal (outside of main::) and an optional warning (inside of main::).
1430 The ability to detect whether a constant had been set with a given name has
1437 This pragma implements the C<\N> string escape. See L<charnames>.
1441 A C<Maxdepth> setting can be specified to avoid venturing
1442 too deeply into deep data structures. See L<Data::Dumper>.
1444 The XSUB implementation of Dump() is now automatically called if the
1445 C<Useqq> setting is not in use.
1447 Dumping C<qr//> objects works correctly.
1451 C<DB> is an experimental module that exposes a clean abstraction
1452 to Perl's debugging API.
1456 DB_File can now be built with Berkeley DB versions 1, 2 or 3.
1457 See C<ext/DB_File/Changes>.
1461 Devel::DProf, a Perl source code profiler has been added. See
1462 L<Devel::DProf> and L<dprofpp>.
1466 The Dumpvalue module provides screen dumps of Perl data.
1470 Overall, Benchmark results exhibit lower average error and better timing
1473 You can now run tests for I<n> seconds instead of guessing the right
1474 number of tests to run: e.g., timethese(-5, ...) will run each
1475 code for at least 5 CPU seconds. Zero as the "number of repetitions"
1476 means "for at least 3 CPU seconds". The output format has also
1477 changed. For example:
1479 use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
1481 will now output something like this:
1483 Benchmark: running a, b, each for at least 5 CPU seconds...
1484 a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
1485 b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
1487 New features: "each for at least N CPU seconds...", "wallclock secs",
1488 and the "@ operations/CPU second (n=operations)".
1490 timethese() now returns a reference to a hash of Benchmark objects containing
1491 the test results, keyed on the names of the tests.
1493 timethis() now returns the iterations field in the Benchmark result object
1496 timethese(), timethis(), and the new cmpthese() (see below) can also take
1497 a format specifier of 'none' to suppress output.
1499 A new function countit() is just like timeit() except that it takes a
1500 TIME instead of a COUNT.
1502 A new function cmpthese() prints a chart comparing the results of each test
1503 returned from a timethese() call. For each possible pair of tests, the
1504 percentage speed difference (iters/sec or seconds/iter) is shown.
1506 For other details, see L<Benchmark>.
1510 The Devel::Peek module provides access to the internal representation
1511 of Perl variables and data. It is a data debugging tool for the XS programmer.
1515 $PERL_VERSION now stands for C<$^V> (a string value) rather than for C<$]>
1520 Env now supports accessing environment variables like PATH as array
1525 More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for
1526 large file (more than 4GB) access (NOTE: the O_LARGEFILE is
1527 automatically added to sysopen() flags if large file support has been
1528 configured, as is the default), Free/Net/OpenBSD locking behaviour
1529 flags F_FLOCK, F_POSIX, Linux F_SHLCK, and O_ACCMODE: the combined
1530 mask of O_RDONLY, O_WRONLY, and O_RDWR. The seek()/sysseek()
1531 constants SEEK_SET, SEEK_CUR, and SEEK_END are available via the
1532 C<:seek> tag. The chmod()/stat() S_IF* constants and S_IS* functions
1533 are available via the C<:mode> tag.
1537 A compare_text() function has been added, which allows custom
1538 comparison functions. See L<File::Compare>.
1542 File::Find now works correctly when the wanted() function is either
1543 autoloaded or is a symbolic reference.
1545 A bug that caused File::Find to lose track of the working directory
1546 when pruning top-level directories has been fixed.
1548 File::Find now also supports several other options to control its
1549 behavior. It can follow symbolic links if the C<follow> option is
1550 specified. Enabling the C<no_chdir> option will make File::Find skip
1551 changing the current directory when walking directories. The C<untaint>
1552 flag can be useful when running with taint checks enabled.
1558 This extension implements BSD-style file globbing. By default,
1559 it will also be used for the internal implementation of the glob()
1560 operator. See L<File::Glob>.
1564 New methods have been added to the File::Spec module: devnull() returns
1565 the name of the null device (/dev/null on Unix) and tmpdir() the name of
1566 the temp directory (normally /tmp on Unix). There are now also methods
1567 to convert between absolute and relative filenames: abs2rel() and
1568 rel2abs(). For compatibility with operating systems that specify volume
1569 names in file paths, the splitpath(), splitdir(), and catdir() methods
1572 =item File::Spec::Functions
1574 The new File::Spec::Functions modules provides a function interface
1575 to the File::Spec module. Allows shorthand
1577 $fullname = catfile($dir1, $dir2, $file);
1581 $fullname = File::Spec->catfile($dir1, $dir2, $file);
1585 Getopt::Long licensing has changed to allow the Perl Artistic License
1586 as well as the GPL. It used to be GPL only, which got in the way of
1587 non-GPL applications that wanted to use Getopt::Long.
1589 Getopt::Long encourages the use of Pod::Usage to produce help
1590 messages. For example:
1596 GetOptions('help|?' => \$help, man => \$man) or pod2usage(2);
1597 pod2usage(1) if $help;
1598 pod2usage(-exitstatus => 0, -verbose => 2) if $man;
1604 sample - Using GetOpt::Long and Pod::Usage
1608 sample [options] [file ...]
1611 -help brief help message
1612 -man full documentation
1620 Print a brief help message and exits.
1624 Prints the manual page and exits.
1630 B<This program> will read the given input file(s) and do someting
1631 useful with the contents thereof.
1635 See L<Pod::Usage> for details.
1637 A bug that prevented the non-option call-back <> from being
1638 specified as the first argument has been fixed.
1640 To specify the characters < and > as option starters, use ><. Note,
1641 however, that changing option starters is strongly deprecated.
1645 write() and syswrite() will now accept a single-argument
1646 form of the call, for consistency with Perl's syswrite().
1648 You can now create a TCP-based IO::Socket::INET without forcing
1649 a connect attempt. This allows you to configure its options
1650 (like making it non-blocking) and then call connect() manually.
1652 A bug that prevented the IO::Socket::protocol() accessor
1653 from ever returning the correct value has been corrected.
1655 IO::Socket::connect now uses non-blocking IO instead of alarm()
1656 to do connect timeouts.
1658 IO::Socket::accept now uses select() instead of alarm() for doing
1661 IO::Socket::INET->new now sets $! correctly on failure. $@ is
1662 still set for backwards compatability.
1666 Java Perl Lingo is now distributed with Perl. See jpl/README
1667 for more information.
1671 C<use lib> now weeds out any trailing duplicate entries.
1672 C<no lib> removes all named entries.
1676 The bitwise operations C<<< << >>>, C<<< >> >>>, C<&>, C<|>,
1677 and C<~> are now supported on bigints.
1681 The accessor methods Re, Im, arg, abs, rho, and theta can now also
1682 act as mutators (accessor $z->Re(), mutator $z->Re(3)).
1684 The class method C<display_format> and the corresponding object method
1685 C<display_format>, in addition to accepting just one argument, now can
1686 also accept a parameter hash. Recognized keys of a parameter hash are
1687 C<"style">, which corresponds to the old one parameter case, and two
1688 new parameters: C<"format">, which is a printf()-style format string
1689 (defaults usually to C<"%.15g">, you can revert to the default by
1690 setting the format string to C<undef>) used for both parts of a
1691 complex number, and C<"polar_pretty_print"> (defaults to true),
1692 which controls whether an attempt is made to try to recognize small
1693 multiples and rationals of pi (2pi, pi/2) at the argument (angle) of a
1694 polar complex number.
1696 The potentially disruptive change is that in list context both methods
1697 now I<return the parameter hash>, instead of only the value of the
1698 C<"style"> parameter.
1702 A little bit of radial trigonometry (cylindrical and spherical),
1703 radial coordinate conversions, and the great circle distance were added.
1705 =item Pod::Parser, Pod::InputObjects
1707 Pod::Parser is a base class for parsing and selecting sections of
1708 pod documentation from an input stream. This module takes care of
1709 identifying pod paragraphs and commands in the input and hands off the
1710 parsed paragraphs and commands to user-defined methods which are free
1711 to interpret or translate them as they see fit.
1713 Pod::InputObjects defines some input objects needed by Pod::Parser, and
1714 for advanced users of Pod::Parser that need more about a command besides
1717 As of release 5.6.0 of Perl, Pod::Parser is now the officially sanctioned
1718 "base parser code" recommended for use by all pod2xxx translators.
1719 Pod::Text (pod2text) and Pod::Man (pod2man) have already been converted
1720 to use Pod::Parser and efforts to convert Pod::HTML (pod2html) are already
1721 underway. For any questions or comments about pod parsing and translating
1722 issues and utilities, please use the pod-people@perl.org mailing list.
1724 For further information, please see L<Pod::Parser> and L<Pod::InputObjects>.
1726 =item Pod::Checker, podchecker
1728 This utility checks pod files for correct syntax, according to
1729 L<perlpod>. Obvious errors are flagged as such, while warnings are
1730 printed for mistakes that can be handled gracefully. The checklist is
1731 not complete yet. See L<Pod::Checker>.
1733 =item Pod::ParseUtils, Pod::Find
1735 These modules provide a set of gizmos that are useful mainly for pod
1736 translators. L<Pod::Find|Pod::Find> traverses directory structures and
1737 returns found pod files, along with their canonical names (like
1738 C<File::Spec::Unix>). L<Pod::ParseUtils|Pod::ParseUtils> contains
1739 B<Pod::List> (useful for storing pod list information), B<Pod::Hyperlink>
1740 (for parsing the contents of C<LE<lt>E<gt>> sequences) and B<Pod::Cache>
1741 (for caching information about pod files, e.g., link nodes).
1743 =item Pod::Select, podselect
1745 Pod::Select is a subclass of Pod::Parser which provides a function
1746 named "podselect()" to filter out user-specified sections of raw pod
1747 documentation from an input stream. podselect is a script that provides
1748 access to Pod::Select from other scripts to be used as a filter.
1751 =item Pod::Usage, pod2usage
1753 Pod::Usage provides the function "pod2usage()" to print usage messages for
1754 a Perl script based on its embedded pod documentation. The pod2usage()
1755 function is generally useful to all script authors since it lets them
1756 write and maintain a single source (the pods) for documentation, thus
1757 removing the need to create and maintain redundant usage message text
1758 consisting of information already in the pods.
1760 There is also a pod2usage script which can be used from other kinds of
1761 scripts to print usage messages from pods (even for non-Perl scripts
1762 with pods embedded in comments).
1764 For details and examples, please see L<Pod::Usage>.
1766 =item Pod::Text and Pod::Man
1768 Pod::Text has been rewritten to use Pod::Parser. While pod2text() is
1769 still available for backwards compatibility, the module now has a new
1770 preferred interface. See L<Pod::Text> for the details. The new Pod::Text
1771 module is easily subclassed for tweaks to the output, and two such
1772 subclasses (Pod::Text::Termcap for man-page-style bold and underlining
1773 using termcap information, and Pod::Text::Color for markup with ANSI color
1774 sequences) are now standard.
1776 pod2man has been turned into a module, Pod::Man, which also uses
1777 Pod::Parser. In the process, several outstanding bugs related to quotes
1778 in section headers, quoting of code escapes, and nested lists have been
1779 fixed. pod2man is now a wrapper script around this module.
1783 An EXISTS method has been added to this module (and sdbm_exists() has
1784 been added to the underlying sdbm library), so one can now call exists
1785 on an SDBM_File tied hash and get the correct result, rather than a
1788 A bug that may have caused data loss when more than one disk block
1789 happens to be read from the database in a single FETCH() has been
1794 Sys::Syslog now uses XSUBs to access facilities from syslog.h so it
1795 no longer requires syslog.ph to exist.
1799 Sys::Hostname now uses XSUBs to call the C library's gethostname() or
1800 uname() if they exist.
1802 =item Term::ANSIColor
1804 Term::ANSIColor is a very simple module to provide easy and readable
1805 access to the ANSI color and highlighting escape sequences, supported by
1806 most ANSI terminal emulators. It is now included standard.
1810 The timelocal() and timegm() functions used to silently return bogus
1811 results when the date fell outside the machine's integer range. They
1812 now consistently croak() if the date falls in an unsupported range.
1816 The error return value in list context has been changed for all functions
1817 that return a list of values. Previously these functions returned a list
1818 with a single element C<undef> if an error occurred. Now these functions
1819 return the empty list in these situations. This applies to the following
1825 The remaining functions are unchanged and continue to return C<undef> on
1826 error even in list context.
1828 The Win32::SetLastError(ERROR) function has been added as a complement
1829 to the Win32::GetLastError() function.
1831 The new Win32::GetFullPathName(FILENAME) returns the full absolute
1832 pathname for FILENAME in scalar context. In list context it returns
1833 a two-element list containing the fully qualified directory name and
1834 the filename. See L<Win32>.
1838 A new feature called "DBM Filters" has been added to all the
1839 DBM modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File.
1840 DBM Filters add four new methods to each DBM module:
1847 These can be used to filter key-value pairs before the pairs are
1848 written to the database or just after they are read from the database.
1849 See L<perldbmfilter> for further information.
1855 C<use attrs> is now obsolete, and is only provided for
1856 backward-compatibility. It's been replaced by the C<sub : attributes>
1857 syntax. See L<perlsub/"Subroutine Attributes"> and L<attributes>.
1859 Lexical warnings pragma, C<use warnings;>, to control optional warnings.
1862 C<use filetest> to control the behaviour of filetests (C<-r> C<-w>
1863 ...). Currently only one subpragma implemented, "use filetest
1864 'access';", that uses access(2) or equivalent to check permissions
1865 instead of using stat(2) as usual. This matters in filesystems
1866 where there are ACLs (access control lists): the stat(2) might lie,
1867 but access(2) knows better.
1869 =head1 Utility Changes
1873 C<perlcc> now supports the C and Bytecode backends. By default,
1874 it generates output from the simple C backend rather than the
1875 optimized C backend.
1877 Support for non-Unix platforms has been improved.
1881 C<perldoc> has been reworked to avoid possible security holes.
1882 It will not by default let itself be run as the superuser, but you
1883 may still use the B<-U> switch to try to make it drop privileges
1886 =head2 The Perl Debugger
1888 Many bug fixes and enhancements were added to F<perl5db.pl>, the
1889 Perl debugger. The help documentation was rearranged. New commands
1890 include C<< < ? >>, C<< > ? >>, and C<< { ? >> to list out current
1891 actions, C<man I<docpage>> to run your doc viewer on some perl
1892 docset, and support for quoted options. The help information was
1893 rearranged, and should be viewable once again if you're using B<less>
1894 as your pager. A serious security hole was plugged--you should
1895 immediately remove all older versions of the Perl debugger as
1896 installed in previous releases, all the way back to perl3, from
1897 your system to avoid being bitten by this.
1899 =head1 Documentation Changes
1905 The official list of public Perl API functions.
1907 =item perlcompile.pod
1909 An introduction to using the Perl Compiler suite.
1913 All material unrelated to running the Perl debugger, plus all
1914 low-level guts-like details that risked crushing the casual user
1915 of the debugger, have been relocated from the old manpage to the
1918 =item perldebguts.pod
1920 This new manpage contains excessively low-level material not related
1921 to the Perl debugger, but slightly related to debugging Perl itself.
1922 It also contains some arcane internal details of how the debugging
1923 process works that may only be of interest to developers of Perl
1926 =item perlfilter.pod
1928 An introduction to writing Perl source filters.
1932 Some guidelines for hacking the Perl source code.
1934 =item perlintern.pod
1936 A list of internal functions in the Perl source code.
1937 (List is currently empty.)
1939 =item perlopentut.pod
1941 A tutorial on using open() effectively.
1943 =item perlreftut.pod
1945 A tutorial that introduces the essentials of references.
1949 A tutorial for beginners on object-oriented Perl.
1953 A tutorial on managing class data for object modules.
1955 =item perlunicode.pod
1957 An introduction to Unicode support features in Perl.
1961 =head1 New or Changed Diagnostics
1965 =item "%s" variable %s masks earlier declaration in same %s
1967 (W) A "my" or "our" variable has been redeclared in the current scope or statement,
1968 effectively eliminating all access to the previous instance. This is almost
1969 always a typographical error. Note that the earlier variable will still exist
1970 until the end of the scope or until all closure referents to it are
1973 =item "my sub" not yet implemented
1975 (F) Lexically scoped subroutines are not yet implemented. Don't try that
1978 =item "our" variable %s redeclared
1980 (W) You seem to have already declared the same global once before in the
1981 current lexical scope.
1983 =item '!' allowed only after types %s
1985 (F) The '!' is allowed in pack() and unpack() only after certain types.
1986 See L<perlfunc/pack>.
1988 =item / cannot take a count
1990 (F) You had an unpack template indicating a counted-length string,
1991 but you have also specified an explicit size for the string.
1992 See L<perlfunc/pack>.
1994 =item / must be followed by a, A or Z
1996 (F) You had an unpack template indicating a counted-length string,
1997 which must be followed by one of the letters a, A or Z
1998 to indicate what sort of string is to be unpacked.
1999 See L<perlfunc/pack>.
2001 =item / must be followed by a*, A* or Z*
2003 (F) You had a pack template indicating a counted-length string,
2004 Currently the only things that can have their length counted are a*, A* or Z*.
2005 See L<perlfunc/pack>.
2007 =item / must follow a numeric type
2009 (F) You had an unpack template that contained a '#',
2010 but this did not follow some numeric unpack specification.
2011 See L<perlfunc/pack>.
2013 =item /%s/: Unrecognized escape \\%c passed through
2015 (W) You used a backslash-character combination which is not recognized
2016 by Perl. This combination appears in an interpolated variable or a
2017 C<'>-delimited regular expression. The character was understood literally.
2019 =item /%s/: Unrecognized escape \\%c in character class passed through
2021 (W) You used a backslash-character combination which is not recognized
2022 by Perl inside character classes. The character was understood literally.
2024 =item /%s/ should probably be written as "%s"
2026 (W) You have used a pattern where Perl expected to find a string,
2027 as in the first argument to C<join>. Perl will treat the true
2028 or false result of matching the pattern against $_ as the string,
2029 which is probably not what you had in mind.
2031 =item %s() called too early to check prototype
2033 (W) You've called a function that has a prototype before the parser saw a
2034 definition or declaration for it, and Perl could not check that the call
2035 conforms to the prototype. You need to either add an early prototype
2036 declaration for the subroutine in question, or move the subroutine
2037 definition ahead of the call to get proper prototype checking. Alternatively,
2038 if you are certain that you're calling the function correctly, you may put
2039 an ampersand before the name to avoid the warning. See L<perlsub>.
2041 =item %s argument is not a HASH or ARRAY element
2043 (F) The argument to exists() must be a hash or array element, such as:
2046 $ref->[12]->["susie"]
2048 =item %s argument is not a HASH or ARRAY element or slice
2050 (F) The argument to delete() must be either a hash or array element, such as:
2053 $ref->[12]->["susie"]
2055 or a hash or array slice, such as:
2057 @foo[$bar, $baz, $xyzzy]
2058 @{$ref->[12]}{"susie", "queue"}
2060 =item %s argument is not a subroutine name
2062 (F) The argument to exists() for C<exists &sub> must be a subroutine
2063 name, and not a subroutine call. C<exists &sub()> will generate this error.
2065 =item %s package attribute may clash with future reserved word: %s
2067 (W) A lowercase attribute name was used that had a package-specific handler.
2068 That name might have a meaning to Perl itself some day, even though it
2069 doesn't yet. Perhaps you should use a mixed-case attribute name, instead.
2072 =item (in cleanup) %s
2074 (W) This prefix usually indicates that a DESTROY() method raised
2075 the indicated exception. Since destructors are usually called by
2076 the system at arbitrary points during execution, and often a vast
2077 number of times, the warning is issued only once for any number
2078 of failures that would otherwise result in the same message being
2081 Failure of user callbacks dispatched using the C<G_KEEPERR> flag
2082 could also result in this warning. See L<perlcall/G_KEEPERR>.
2084 =item <> should be quotes
2086 (F) You wrote C<< require <file> >> when you should have written
2089 =item Attempt to join self
2091 (F) You tried to join a thread from within itself, which is an
2092 impossible task. You may be joining the wrong thread, or you may
2093 need to move the join() to some other thread.
2095 =item Bad evalled substitution pattern
2097 (F) You've used the /e switch to evaluate the replacement for a
2098 substitution, but perl found a syntax error in the code to evaluate,
2099 most likely an unexpected right brace '}'.
2101 =item Bad realloc() ignored
2103 (S) An internal routine called realloc() on something that had never been
2104 malloc()ed in the first place. Mandatory, but can be disabled by
2105 setting environment variable C<PERL_BADFREE> to 1.
2107 =item Bareword found in conditional
2109 (W) The compiler found a bareword where it expected a conditional,
2110 which often indicates that an || or && was parsed as part of the
2111 last argument of the previous construct, for example:
2115 It may also indicate a misspelled constant that has been interpreted
2118 use constant TYPO => 1;
2119 if (TYOP) { print "foo" }
2121 The C<strict> pragma is useful in avoiding such errors.
2123 =item Binary number > 0b11111111111111111111111111111111 non-portable
2125 (W) The binary number you specified is larger than 2**32-1
2126 (4294967295) and therefore non-portable between systems. See
2127 L<perlport> for more on portability concerns.
2129 =item Bit vector size > 32 non-portable
2131 (W) Using bit vector sizes larger than 32 is non-portable.
2133 =item Buffer overflow in prime_env_iter: %s
2135 (W) A warning peculiar to VMS. While Perl was preparing to iterate over
2136 %ENV, it encountered a logical name or symbol definition which was too long,
2137 so it was truncated to the string shown.
2139 =item Can't check filesystem of script "%s"
2141 (P) For some reason you can't check the filesystem of the script for nosuid.
2143 =item Can't declare class for non-scalar %s in "%s"
2145 (S) Currently, only scalar variables can declared with a specific class
2146 qualifier in a "my" or "our" declaration. The semantics may be extended
2147 for other types of variables in future.
2149 =item Can't declare %s in "%s"
2151 (F) Only scalar, array, and hash variables may be declared as "my" or
2152 "our" variables. They must have ordinary identifiers as names.
2154 =item Can't ignore signal CHLD, forcing to default
2156 (W) Perl has detected that it is being run with the SIGCHLD signal
2157 (sometimes known as SIGCLD) disabled. Since disabling this signal
2158 will interfere with proper determination of exit status of child
2159 processes, Perl has reset the signal to its default value.
2160 This situation typically indicates that the parent program under
2161 which Perl may be running (e.g., cron) is being very careless.
2163 =item Can't modify non-lvalue subroutine call
2165 (F) Subroutines meant to be used in lvalue context should be declared as
2166 such, see L<perlsub/"Lvalue subroutines">.
2168 =item Can't read CRTL environ
2170 (S) A warning peculiar to VMS. Perl tried to read an element of %ENV
2171 from the CRTL's internal environment array and discovered the array was
2172 missing. You need to figure out where your CRTL misplaced its environ
2173 or define F<PERL_ENV_TABLES> (see L<perlvms>) so that environ is not searched.
2175 =item Can't remove %s: %s, skipping file
2177 (S) You requested an inplace edit without creating a backup file. Perl
2178 was unable to remove the original file to replace it with the modified
2179 file. The file was left unmodified.
2181 =item Can't return %s from lvalue subroutine
2183 (F) Perl detected an attempt to return illegal lvalues (such
2184 as temporary or readonly values) from a subroutine used as an lvalue.
2185 This is not allowed.
2187 =item Can't weaken a nonreference
2189 (F) You attempted to weaken something that was not a reference. Only
2190 references can be weakened.
2192 =item Character class [:%s:] unknown
2194 (F) The class in the character class [: :] syntax is unknown.
2197 =item Character class syntax [%s] belongs inside character classes
2199 (W) The character class constructs [: :], [= =], and [. .] go
2200 I<inside> character classes, the [] are part of the construct,
2201 for example: /[012[:alpha:]345]/. Note that [= =] and [. .]
2202 are not currently implemented; they are simply placeholders for
2205 =item Constant is not %s reference
2207 (F) A constant value (perhaps declared using the C<use constant> pragma)
2208 is being dereferenced, but it amounts to the wrong type of reference. The
2209 message indicates the type of reference that was expected. This usually
2210 indicates a syntax error in dereferencing the constant value.
2211 See L<perlsub/"Constant Functions"> and L<constant>.
2213 =item constant(%s): %%^H is not localized
2215 (F) When setting compile-time-lexicalized hash %^H one should set the
2216 corresponding bit of $^H as well.
2218 =item constant(%s): %s
2220 (F) Compile-time-substitutions (such as overloaded constants and
2221 character names) were not correctly set up.
2223 =item CORE::%s is not a keyword
2225 (F) The CORE:: namespace is reserved for Perl keywords.
2227 =item defined(@array) is deprecated
2229 (D) defined() is not usually useful on arrays because it checks for an
2230 undefined I<scalar> value. If you want to see if the array is empty,
2231 just use C<if (@array) { # not empty }> for example.
2233 =item defined(%hash) is deprecated
2235 (D) defined() is not usually useful on hashes because it checks for an
2236 undefined I<scalar> value. If you want to see if the hash is empty,
2237 just use C<if (%hash) { # not empty }> for example.
2239 =item Did not produce a valid header
2243 =item Did you mean "local" instead of "our"?
2245 (W) Remember that "our" does not localize the declared global variable.
2246 You have declared it again in the same lexical scope, which seems superfluous.
2248 =item Document contains no data
2252 =item entering effective %s failed
2254 (F) While under the C<use filetest> pragma, switching the real and
2255 effective uids or gids failed.
2257 =item false [] range "%s" in regexp
2259 (W) A character class range must start and end at a literal character, not
2260 another character class like C<\d> or C<[:alpha:]>. The "-" in your false
2261 range is interpreted as a literal "-". Consider quoting the "-", "\-".
2264 =item Filehandle %s opened only for output
2266 (W) You tried to read from a filehandle opened only for writing. If you
2267 intended it to be a read/write filehandle, you needed to open it with
2268 "+<" or "+>" or "+>>" instead of with "<" or nothing. If
2269 you intended only to read from the file, use "<". See
2272 =item flock() on closed filehandle %s
2274 (W) The filehandle you're attempting to flock() got itself closed some
2275 time before now. Check your logic flow. flock() operates on filehandles.
2276 Are you attempting to call flock() on a dirhandle by the same name?
2278 =item Global symbol "%s" requires explicit package name
2280 (F) You've said "use strict vars", which indicates that all variables
2281 must either be lexically scoped (using "my"), declared beforehand using
2282 "our", or explicitly qualified to say which package the global variable
2285 =item Hexadecimal number > 0xffffffff non-portable
2287 (W) The hexadecimal number you specified is larger than 2**32-1
2288 (4294967295) and therefore non-portable between systems. See
2289 L<perlport> for more on portability concerns.
2291 =item Ill-formed CRTL environ value "%s"
2293 (W) A warning peculiar to VMS. Perl tried to read the CRTL's internal
2294 environ array, and encountered an element without the C<=> delimiter
2295 used to spearate keys from values. The element is ignored.
2297 =item Ill-formed message in prime_env_iter: |%s|
2299 (W) A warning peculiar to VMS. Perl tried to read a logical name
2300 or CLI symbol definition when preparing to iterate over %ENV, and
2301 didn't see the expected delimiter between key and value, so the
2304 =item Illegal binary digit %s
2306 (F) You used a digit other than 0 or 1 in a binary number.
2308 =item Illegal binary digit %s ignored
2310 (W) You may have tried to use a digit other than 0 or 1 in a binary number.
2311 Interpretation of the binary number stopped before the offending digit.
2313 =item Illegal number of bits in vec
2315 (F) The number of bits in vec() (the third argument) must be a power of
2316 two from 1 to 32 (or 64, if your platform supports that).
2318 =item Integer overflow in %s number
2320 (W) The hexadecimal, octal or binary number you have specified either
2321 as a literal or as an argument to hex() or oct() is too big for your
2322 architecture, and has been converted to a floating point number. On a
2323 32-bit architecture the largest hexadecimal, octal or binary number
2324 representable without overflow is 0xFFFFFFFF, 037777777777, or
2325 0b11111111111111111111111111111111 respectively. Note that Perl
2326 transparently promotes all numbers to a floating point representation
2327 internally--subject to loss of precision errors in subsequent
2330 =item Invalid %s attribute: %s
2332 The indicated attribute for a subroutine or variable was not recognized
2333 by Perl or by a user-supplied handler. See L<attributes>.
2335 =item Invalid %s attributes: %s
2337 The indicated attributes for a subroutine or variable were not recognized
2338 by Perl or by a user-supplied handler. See L<attributes>.
2340 =item invalid [] range "%s" in regexp
2342 The offending range is now explicitly displayed.
2344 =item Invalid separator character %s in attribute list
2346 (F) Something other than a colon or whitespace was seen between the
2347 elements of an attribute list. If the previous attribute
2348 had a parenthesised parameter list, perhaps that list was terminated
2349 too soon. See L<attributes>.
2351 =item Invalid separator character %s in subroutine attribute list
2353 (F) Something other than a colon or whitespace was seen between the
2354 elements of a subroutine attribute list. If the previous attribute
2355 had a parenthesised parameter list, perhaps that list was terminated
2358 =item leaving effective %s failed
2360 (F) While under the C<use filetest> pragma, switching the real and
2361 effective uids or gids failed.
2363 =item Lvalue subs returning %s not implemented yet
2365 (F) Due to limitations in the current implementation, array and hash
2366 values cannot be returned in subroutines used in lvalue context.
2367 See L<perlsub/"Lvalue subroutines">.
2369 =item Method %s not permitted
2373 =item Missing %sbrace%s on \N{}
2375 (F) Wrong syntax of character name literal C<\N{charname}> within
2376 double-quotish context.
2378 =item Missing command in piped open
2380 (W) You used the C<open(FH, "| command")> or C<open(FH, "command |")>
2381 construction, but the command was missing or blank.
2383 =item Missing name in "my sub"
2385 (F) The reserved syntax for lexically scoped subroutines requires that they
2386 have a name with which they can be found.
2388 =item No %s specified for -%c
2390 (F) The indicated command line switch needs a mandatory argument, but
2391 you haven't specified one.
2393 =item No package name allowed for variable %s in "our"
2395 (F) Fully qualified variable names are not allowed in "our" declarations,
2396 because that doesn't make much sense under existing semantics. Such
2397 syntax is reserved for future extensions.
2399 =item No space allowed after -%c
2401 (F) The argument to the indicated command line switch must follow immediately
2402 after the switch, without intervening spaces.
2404 =item no UTC offset information; assuming local time is UTC
2406 (S) A warning peculiar to VMS. Perl was unable to find the local
2407 timezone offset, so it's assuming that local system time is equivalent
2408 to UTC. If it's not, define the logical name F<SYS$TIMEZONE_DIFFERENTIAL>
2409 to translate to the number of seconds which need to be added to UTC to
2412 =item Octal number > 037777777777 non-portable
2414 (W) The octal number you specified is larger than 2**32-1 (4294967295)
2415 and therefore non-portable between systems. See L<perlport> for more
2416 on portability concerns.
2418 See also L<perlport> for writing portable code.
2420 =item panic: del_backref
2422 (P) Failed an internal consistency check while trying to reset a weak
2425 =item panic: kid popen errno read
2427 (F) forked child returned an incomprehensible message about its errno.
2429 =item panic: magic_killbackrefs
2431 (P) Failed an internal consistency check while trying to reset all weak
2432 references to an object.
2434 =item Parentheses missing around "%s" list
2436 (W) You said something like
2442 my ($foo, $bar) = @_;
2444 Remember that "my", "our", and "local" bind tighter than comma.
2446 =item Possible Y2K bug: %s
2448 (W) You are concatenating the number 19 with another number, which
2449 could be a potential Year 2000 problem.
2451 =item pragma "attrs" is deprecated, use "sub NAME : ATTRS" instead
2453 (W) You have written somehing like this:
2457 use attrs qw(locked);
2460 You should use the new declaration syntax instead.
2466 The C<use attrs> pragma is now obsolete, and is only provided for
2467 backward-compatibility. See L<perlsub/"Subroutine Attributes">.
2470 =item Premature end of script headers
2474 =item Repeat count in pack overflows
2476 (F) You can't specify a repeat count so large that it overflows
2477 your signed integers. See L<perlfunc/pack>.
2479 =item Repeat count in unpack overflows
2481 (F) You can't specify a repeat count so large that it overflows
2482 your signed integers. See L<perlfunc/unpack>.
2484 =item realloc() of freed memory ignored
2486 (S) An internal routine called realloc() on something that had already
2489 =item Reference is already weak
2491 (W) You have attempted to weaken a reference that is already weak.
2492 Doing so has no effect.
2494 =item setpgrp can't take arguments
2496 (F) Your system has the setpgrp() from BSD 4.2, which takes no arguments,
2497 unlike POSIX setpgid(), which takes a process ID and process group ID.
2499 =item Strange *+?{} on zero-length expression
2501 (W) You applied a regular expression quantifier in a place where it
2502 makes no sense, such as on a zero-width assertion.
2503 Try putting the quantifier inside the assertion instead. For example,
2504 the way to match "abc" provided that it is followed by three
2505 repetitions of "xyz" is C</abc(?=(?:xyz){3})/>, not C</abc(?=xyz){3}/>.
2507 =item switching effective %s is not implemented
2509 (F) While under the C<use filetest> pragma, we cannot switch the
2510 real and effective uids or gids.
2512 =item This Perl can't reset CRTL environ elements (%s)
2514 =item This Perl can't set CRTL environ elements (%s=%s)
2516 (W) Warnings peculiar to VMS. You tried to change or delete an element
2517 of the CRTL's internal environ array, but your copy of Perl wasn't
2518 built with a CRTL that contained the setenv() function. You'll need to
2519 rebuild Perl with a CRTL that does, or redefine F<PERL_ENV_TABLES> (see
2520 L<perlvms>) so that the environ array isn't the target of the change to
2521 %ENV which produced the warning.
2523 =item Unknown open() mode '%s'
2525 (F) The second argument of 3-argument open() is not among the list
2526 of valid modes: C<< < >>, C<< > >>, C<<< >> >>>, C<< +< >>,
2527 C<< +> >>, C<<< +>> >>>, C<-|>, C<|->.
2529 =item Unknown process %x sent message to prime_env_iter: %s
2531 (P) An error peculiar to VMS. Perl was reading values for %ENV before
2532 iterating over it, and someone else stuck a message in the stream of
2533 data Perl expected. Someone's very confused, or perhaps trying to
2534 subvert Perl's population of %ENV for nefarious purposes.
2536 =item Unrecognized escape \\%c passed through
2538 (W) You used a backslash-character combination which is not recognized
2539 by Perl. The character was understood literally.
2541 =item Unterminated attribute parameter in attribute list
2543 (F) The lexer saw an opening (left) parenthesis character while parsing an
2544 attribute list, but the matching closing (right) parenthesis
2545 character was not found. You may need to add (or remove) a backslash
2546 character to get your parentheses to balance. See L<attributes>.
2548 =item Unterminated attribute list
2550 (F) The lexer found something other than a simple identifier at the start
2551 of an attribute, and it wasn't a semicolon or the start of a
2552 block. Perhaps you terminated the parameter list of the previous attribute
2553 too soon. See L<attributes>.
2555 =item Unterminated attribute parameter in subroutine attribute list
2557 (F) The lexer saw an opening (left) parenthesis character while parsing a
2558 subroutine attribute list, but the matching closing (right) parenthesis
2559 character was not found. You may need to add (or remove) a backslash
2560 character to get your parentheses to balance.
2562 =item Unterminated subroutine attribute list
2564 (F) The lexer found something other than a simple identifier at the start
2565 of a subroutine attribute, and it wasn't a semicolon or the start of a
2566 block. Perhaps you terminated the parameter list of the previous attribute
2569 =item Value of CLI symbol "%s" too long
2571 (W) A warning peculiar to VMS. Perl tried to read the value of an %ENV
2572 element from a CLI symbol table, and found a resultant string longer
2573 than 1024 characters. The return value has been truncated to 1024
2576 =item Version number must be a constant number
2578 (P) The attempt to translate a C<use Module n.n LIST> statement into
2579 its equivalent C<BEGIN> block found an internal inconsistency with
2584 =head1 Obsolete Diagnostics
2588 =item Character class syntax [: :] is reserved for future extensions
2590 (W) Within regular expression character classes ([]) the syntax beginning
2591 with "[:" and ending with ":]" is reserved for future extensions.
2592 If you need to represent those character sequences inside a regular
2593 expression character class, just quote the square brackets with the
2594 backslash: "\[:" and ":\]".
2596 =item Ill-formed logical name |%s| in prime_env_iter
2598 (W) A warning peculiar to VMS. A logical name was encountered when preparing
2599 to iterate over %ENV which violates the syntactic rules governing logical
2600 names. Because it cannot be translated normally, it is skipped, and will not
2601 appear in %ENV. This may be a benign occurrence, as some software packages
2602 might directly modify logical name tables and introduce nonstandard names,
2603 or it may indicate that a logical name table has been corrupted.
2605 =item Probable precedence problem on %s
2607 (W) The compiler found a bareword where it expected a conditional,
2608 which often indicates that an || or && was parsed as part of the
2609 last argument of the previous construct, for example:
2613 =item regexp too big
2615 (F) The current implementation of regular expressions uses shorts as
2616 address offsets within a string. Unfortunately this means that if
2617 the regular expression compiles to longer than 32767, it'll blow up.
2618 Usually when you want a regular expression this big, there is a better
2619 way to do it with multiple statements. See L<perlre>.
2621 =item Use of "$$<digit>" to mean "${$}<digit>" is deprecated
2623 (D) Perl versions before 5.004 misinterpreted any type marker followed
2624 by "$" and a digit. For example, "$$0" was incorrectly taken to mean
2625 "${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004.
2627 However, the developers of Perl 5.004 could not fix this bug completely,
2628 because at least two widely-used modules depend on the old meaning of
2629 "$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the
2630 old (broken) way inside strings; but it generates this message as a
2631 warning. And in Perl 5.005, this special treatment will cease.
2635 =head1 Known Problems
2637 =head2 Thread tests failing
2639 The subtests 19 and 20 of the lib/thread test are known to fail in
2642 =head2 EBCDIC platforms not supported
2644 In earlier releases of Perl the EBCDIC environments like OS390 (also
2645 known as Open Edition MVS) and VM-ESA were supported. Due to the
2646 changes required by the UTF-8 (Unicode) support in Perl 5.6 the EBCDIC
2647 platforms are not supported in Perl 5.6.0.
2649 =head2 NEXTSTEP 3.3 POSIX test failure
2651 In NEXTSTEP 3.3p2 the implementation of the strftime(3) in the
2652 operating system libraries is buggy: the %j format numbers the days of
2653 a month starting from zero, which, while being logical to programmers,
2654 will cause the subtests 19 to 27 of the lib/posix test may fail.
2656 =head2 UNICOS/mk CC failures during Configure run
2658 In UNICOS/mk the following errors may appear during the Configure run:
2660 Guessing which symbols your C compiler and preprocessor define...
2661 CC-20 cc: ERROR File = try.c, Line = 3
2663 bad switch yylook 79bad switch yylook 79bad switch yylook 79bad switch yylook 79#ifdef A29K
2665 4 errors detected in the compilation of "try.c".
2667 The culprit is the broken awk of UNICOS/mk. The effect is fortunately
2668 rather mild: Perl itself is not adversely affected by the error, only
2669 the h2ph utility coming with Perl, and that is rather rarely needed
2672 =head2 Many features still experimental
2674 As discussed above, many features are still experimental, to a greater
2675 or lesser degree. Interfaces and implementation are subject to
2676 change, in extreme cases even subject to removal in some future
2677 release of Perl. These features include the following:
2685 =item Lvalue subroutines
2687 =item Weak references
2689 =item File globbing now implemented internally
2691 =item The Compiler suite
2695 =item the regular expression constructs C<(?{ code })> and C<(??{ code })>
2701 If you find what you think is a bug, you might check the
2702 articles recently posted to the comp.lang.perl.misc newsgroup.
2703 There may also be information at http://www.perl.com/perl/, the Perl
2706 If you believe you have an unreported bug, please run the B<perlbug>
2707 program included with your release. Be sure to trim your bug down
2708 to a tiny but sufficient test case. Your bug report, along with the
2709 output of C<perl -V>, will be sent off to perlbug@perl.com to be
2710 analysed by the Perl porting team.
2714 The F<Changes> file for exhaustive details on what changed.
2716 The F<INSTALL> file for how to build Perl.
2718 The F<README> file for general stuff.
2720 The F<Artistic> and F<Copying> files for copyright information.
2724 Written by Gurusamy Sarathy <F<gsar@activestate.com>>, with many
2725 contributions from The Perl Porters.
2727 Send omissions or corrections to <F<perlbug@perl.com>>.