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 passwd and shell returned by the getpwxxx() are now tainted
211 Because the user can affect her own encrypted password and login shell
212 the password and shell returned by the getpwent(), getpwnam(), and
213 getpwuid() functions are tainted.
215 =head2 The msgrcv() and shmread() now taint
217 Because other (untrusted) processes can modify messages and shared
218 memory segments for their own nefarious purposes, the messages
219 returned by msgrcv() (and its object-oriented interface,
220 IPC::SysV::Msg::rcv) and the variable modified by shmread() are tainted.
224 =head2 C Source Incompatibilities
228 =item C<PERL_POLLUTE>
230 Release 5.005 grandfathered old global symbol names by providing preprocessor
231 macros for extension source compatibility. As of release 5.6.0, these
232 preprocessor definitions are not available by default. You need to explicitly
233 compile perl with C<-DPERL_POLLUTE> to get these definitions. For
234 extensions still using the old symbols, this option can be
235 specified via MakeMaker:
237 perl Makefile.PL POLLUTE=1
239 =item C<PERL_IMPLICIT_CONTEXT>
241 NOTE: PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
242 with one of -Dusethreads, -Dusemultiplicity, or both. It is not
243 intended to be enabled by users at this time.
245 This new build option provides a set of macros for all API functions
246 such that an implicit interpreter/thread context argument is passed to
247 every API function. As a result of this, something like C<sv_setsv(foo,bar)>
248 amounts to a macro invocation that actually translates to something like
249 C<Perl_sv_setsv(my_perl,foo,bar)>. While this is generally expected
250 to not have any significant source compatibility issues, the difference
251 between a macro and a real function call will need to be considered.
253 This means that there B<is> a source compatibility issue as a result of
254 this if your extensions attempt to use pointers to any of the Perl API
257 Note that the above issue is not relevant to the default build of
258 Perl, whose interfaces continue to match those of prior versions
259 (but subject to the other options described here).
261 See L<perlguts/"The Perl API"> for detailed information on the
262 ramifications of building Perl with this option.
264 =item C<PERL_POLLUTE_MALLOC>
266 Enabling Perl's malloc in release 5.005 and earlier caused the namespace of
267 the system's malloc family of functions to be usurped by the Perl versions,
268 since by default they used the same names. Besides causing problems on
269 platforms that do not allow these functions to be cleanly replaced, this
270 also meant that the system versions could not be called in programs that
271 used Perl's malloc. Previous versions of Perl have allowed this behaviour
272 to be suppressed with the HIDEMYMALLOC and EMBEDMYMALLOC preprocessor
275 As of release 5.6.0, Perl's malloc family of functions have default names
276 distinct from the system versions. You need to explicitly compile perl with
277 C<-DPERL_POLLUTE_MALLOC> to get the older behaviour. HIDEMYMALLOC
278 and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now
281 Note that these functions do B<not> constitute Perl's memory allocation API.
282 See L<perlguts/"Memory Allocation"> for further information about that.
286 =head2 Compatible C Source API Changes
290 =item C<PATCHLEVEL> is now C<PERL_VERSION>
292 The cpp macros C<PERL_REVISION>, C<PERL_VERSION>, and C<PERL_SUBVERSION>
293 are now available by default from perl.h, and reflect the base revision,
294 patchlevel, and subversion respectively. C<PERL_REVISION> had no
295 prior equivalent, while C<PERL_VERSION> and C<PERL_SUBVERSION> were
296 previously available as C<PATCHLEVEL> and C<SUBVERSION>.
298 The new names cause less pollution of the B<cpp> namespace and reflect what
299 the numbers have come to stand for in common practice. For compatibility,
300 the old names are still supported when F<patchlevel.h> is explicitly
301 included (as required before), so there is no source incompatibility
306 =head2 Binary Incompatibilities
308 In general, the default build of this release is expected to be binary
309 compatible for extensions built with the 5.005 release or its maintenance
310 versions. However, specific platforms may have broken binary compatibility
311 due to changes in the defaults used in hints files. Therefore, please be
312 sure to always check the platform-specific README files for any notes to
315 The usethreads or usemultiplicity builds are B<not> binary compatible
316 with the corresponding builds in 5.005.
318 On platforms that require an explicit list of exports (AIX, OS/2 and Windows,
319 among others), purely internal symbols such as parser functions and the
320 run time opcodes are not exported by default. Perl 5.005 used to export
321 all functions irrespective of whether they were considered part of the
324 For the full list of public API functions, see L<perlapi>.
326 =head1 Installation and Configuration Improvements
328 =head2 -Dusethreads means something different
330 WARNING: Support for threads continues to be an experimental feature.
331 Interfaces and implementation are subject to sudden and drastic changes.
333 The -Dusethreads flag now enables the experimental interpreter-based thread
334 support by default. To get the flavor of experimental threads that was in
335 5.005 instead, you need to run Configure with "-Dusethreads -Duse5005threads".
337 As of v5.6.0, interpreter-threads support is still lacking a way to
338 create new threads from Perl (i.e., C<use Thread;> will not work with
339 interpreter threads). C<use Thread;> continues to be available when you
340 specify the -Duse5005threads option to Configure, bugs and all.
342 =head2 New Configure flags
344 The following new flags may be enabled on the Configure command line
345 by running Configure with C<-Dflag>.
348 usethreads useithreads (new interpreter threads: no Perl API yet)
349 usethreads use5005threads (threads as they were in 5.005)
351 use64bitint (equal to now deprecated 'use64bits')
357 usesocks (only SOCKS v5 supported)
359 =head2 Threadedness and 64-bitness now more daring
361 The Configure options enabling the use of threads and the use of
362 64-bitness are now more daring in the sense that they no more have an
363 explicit list of operating systems of known threads/64-bit
364 capabilities. In other words: if your operating system has the
365 necessary APIs and datatypes, you should be able just to go ahead and
366 use them, for threads by Configure -Dusethreads, and for 64 bits
367 either explicitly by Configure -Duse64bitint or implicitly if your
368 system has 64-bit wide datatypes. See also L<"64-bit support">.
372 Some platforms have "long doubles", floating point numbers of even
373 larger range than ordinary "doubles". To enable using long doubles for
374 Perl's scalars, use -Duselongdouble.
378 You can enable both -Duse64bitint and -Duselongdouble with -Dusemorebits.
379 See also L<"64-bit support">.
381 =head2 -Duselargefiles
383 Some platforms support system APIs that are capable of handling large files
384 (typically, files larger than two gigabytes). Perl will try to use these
385 APIs if you ask for -Duselargefiles.
387 See L<"Large file support"> for more information.
389 =head2 installusrbinperl
391 You can use "Configure -Uinstallusrbinperl" which causes installperl
392 to skip installing perl also as /usr/bin/perl. This is useful if you
393 prefer not to modify /usr/bin for some reason or another but harmful
394 because many scripts assume to find Perl in /usr/bin/perl.
398 You can use "Configure -Dusesocks" which causes Perl to probe
399 for the SOCKS proxy protocol library (v5, not v4). For more information
402 http://www.socks.nec.com/
406 You can "post-edit" the Configure variables using the Configure C<-A>
407 switch. The editing happens immediately after the platform specific
408 hints files have been processed but before the actual configuration
409 process starts. Run C<Configure -h> to find out the full C<-A> syntax.
411 =head2 Enhanced Installation Directories
413 The installation structure has been enriched to improve the support
414 for maintaining multiple versions of perl, to provide locations for
415 vendor-supplied modules, scripts, and manpages, and to ease maintenance
416 of locally-added modules, scripts, and manpages. See the section on
417 Installation Directories in the INSTALL file for complete details.
418 For most users building and installing from source, the defaults should
421 If you previously used C<Configure -Dsitelib> or C<-Dsitearch> to set
422 special values for library directories, you might wish to consider using
423 the new C<-Dsiteprefix> setting instead. Also, if you wish to re-use a
424 config.sh file from an earlier version of perl, you should be sure to
425 check that Configure makes sensible choices for the new directories.
426 See INSTALL for complete details.
430 =head2 Unicode and UTF-8 support
432 WARNING: This is an experimental feature. Implementation details are
435 Perl now uses UTF-8 as its internal representation for character
436 strings. The C<utf8> and C<bytes> pragmas are used to control this support
437 in the current lexical scope. See L<perlunicode>, L<utf8> and L<bytes> for
440 =head2 Interpreter cloning, threads, and concurrency
442 WARNING: This is an experimental feature. Implementation details are
445 Perl 5.005_63 introduces the beginnings of support for running multiple
446 interpreters concurrently in different threads. In conjunction with
447 the perl_clone() API call, which can be used to selectively duplicate
448 the state of any given interpreter, it is possible to compile a
449 piece of code once in an interpreter, clone that interpreter
450 one or more times, and run all the resulting interpreters in distinct
453 On Windows, this feature is used to emulate fork() at the interpreter
454 level. See L<perlfork>.
456 This feature is still in evolution. It is eventually meant to be used
457 to selectively clone a subroutine and data reachable from that
458 subroutine in a separate interpreter and run the cloned subroutine
459 in a separate thread. Since there is no shared data between the
460 interpreters, little or no locking will be needed (unless parts of
461 the symbol table are explicitly shared). This is obviously intended
462 to be an easy-to-use replacement for the existing threads support.
464 Support for cloning interpreters and interpreter concurrency can be
465 enabled using the -Dusethreads Configure option (see win32/Makefile for
466 how to enable it on Windows.) The resulting perl executable will be
467 functionally identical to one that was built with -Dmultiplicity, but
468 the perl_clone() API call will only be available in the former.
470 -Dusethreads enables the cpp macro USE_ITHREADS by default, which in turn
471 enables Perl source code changes that provide a clear separation between
472 the op tree and the data it operates with. The former is immutable, and
473 can therefore be shared between an interpreter and all of its clones,
474 while the latter is considered local to each interpreter, and is therefore
475 copied for each clone.
477 Note that building Perl with the -Dusemultiplicity Configure option
478 is adequate if you wish to run multiple B<independent> interpreters
479 concurrently in different threads. -Dusethreads only provides the
480 additional functionality of the perl_clone() API call and other
481 support for running B<cloned> interpreters concurrently.
483 =head2 Lexically scoped warning categories
485 You can now control the granularity of warnings emitted by perl at a finer
486 level using the C<use warnings> pragma. See L<warnings> and L<perllexwarn>
489 =head2 Lvalue subroutines
491 WARNING: This is an experimental feature. Details are subject to change.
493 Subroutines can now return modifiable lvalues.
494 See L<perlsub/"Lvalue subroutines">.
496 =head2 "our" declarations
498 An "our" declaration introduces a value that can be best understood
499 as a lexically scoped symbolic alias to a global variable in the
500 package that was current where the variable was declared. This is
501 mostly useful as an alternative to the C<vars> pragma, but also provides
502 the opportunity to introduce typing and other attributes for such
503 variables. See L<perlfunc/our>.
505 =head2 Support for strings represented as a vector of ordinals
507 Literals of the form C<v1.2.3.4> are now parsed as a string composed of
508 of characters with the specified ordinals. This is an alternative, more
509 readable way to construct (possibly unicode) strings instead of
510 interpolating characters, as in C<"\x{1}\x{2}\x{3}\x{4}">. The leading
511 C<v> may be omitted if there are more than two ordinals, so C<1.2.3> is
512 parsed the same as C<v1.2.3>.
514 Strings written in this form are also useful to represent version "numbers".
515 It is easy to compare such version "numbers" (which are really just plain
516 strings) using any of the usual string comparison operators C<eq>, C<ne>,
517 C<lt>, C<gt>, etc., or perform bitwise string operations on them using C<|>,
520 In conjunction with the new C<$^V> magic variable (which contains
521 the perl version as a string), such literals can be used as a readable way
522 to check if you're running a particular version of Perl:
524 # this will parse in older versions of Perl also
525 if ($^V and $^V gt v5.6.0) {
526 # new features supported
529 C<require> and C<use> also have some special magic to support such literals.
530 They will be interpreted as a version rather than as a module name:
532 require v5.6.0; # croak if $^V lt v5.6.0
533 use v5.6.0; # same, but croaks at compile-time
535 Alternatively, the C<v> may be omitted if there is more than one dot:
540 Also, C<sprintf> and C<printf> support the Perl-specific format flag C<%v>
541 to print ordinals of characters in arbitrary strings:
543 printf "v%vd", $^V; # prints current version, such as "v5.5.650"
544 printf "%*vX", ":", $addr; # formats IPv6 address
545 printf "%*vb", " ", $bits; # displays bitstring
547 See L<perldata/"Scalar value constructors"> for additional information.
549 =head2 Weak references
551 WARNING: This is an experimental feature. Details are subject to change.
553 In previous versions of Perl, you couldn't cache objects so as
554 to allow them to be deleted if the last reference from outside
555 the cache is deleted. The reference in the cache would hold a
556 reference count on the object and the objects would never be
559 Another familiar problem is with circular references. When an
560 object references itself, its reference count would never go
561 down to zero, and it would not get destroyed until the program
564 Weak references solve this by allowing you to "weaken" any
565 reference, that is, make it not count towards the reference count.
566 When the last non-weak reference to an object is deleted, the object
567 is destroyed and all the weak references to the object are
568 automatically undef-ed.
570 To use this feature, you need the WeakRef package from CPAN, which
571 contains additional documentation.
573 =head2 File globbing implemented internally
575 WARNING: This is currently an experimental feature. Interfaces and
576 implementation are likely to change.
578 Perl now uses the File::Glob implementation of the glob() operator
579 automatically. This avoids using an external csh process and the
580 problems associated with it.
582 =head2 Binary numbers supported
584 Binary numbers are now supported as literals, in s?printf formats, and
588 printf "The answer is: %b\n", oct("0b101010");
590 =head2 Some arrows may be omitted in calls through references
592 Perl now allows the arrow to be omitted in many constructs
593 involving subroutine calls through references. For example,
594 C<< $foo[10]->('foo') >> may now be written C<$foo[10]('foo')>.
595 This is rather similar to how the arrow may be omitted from
596 C<< $foo[10]->{'foo'} >>. Note however, that the arrow is still
597 required for C<< foo(10)->('bar') >>.
599 =head2 exists() is supported on subroutine names
601 The exists() builtin now works on subroutine names. A subroutine
602 is considered to exist if it has been declared (even if implicitly).
603 See L<perlfunc/exists> for examples.
605 =head2 exists() and delete() are supported on array elements
607 The exists() and delete() builtins now work on simple arrays as well.
608 The behavior is similar to that on hash elements.
610 exists() can be used to check whether an array element has been
611 initialized. This avoids autovivifying array elements that don't exist.
612 If the array is tied, the EXISTS() method in the corresponding tied
613 package will be invoked.
615 delete() may be used to remove an element from the array and return
616 it. The array element at that position returns to its unintialized
617 state, so that testing for the same element with exists() will return
618 false. If the element happens to be the one at the end, the size of
619 the array also shrinks up to the highest element that tests true for
620 exists(), or 0 if none such is found. If the array is tied, the DELETE()
621 method in the corresponding tied package will be invoked.
623 See L<perlfunc/exists> and L<perlfunc/delete> for examples.
625 =head2 syswrite() ease-of-use
627 The length argument of C<syswrite()> has become optional.
629 =head2 File and directory handles can be autovivified
631 Similar to how constructs such as C<< $x->[0] >> autovivify a reference,
632 handle constructors (open(), opendir(), pipe(), socketpair(), sysopen(),
633 socket(), and accept()) now autovivify a file or directory handle
634 if the handle passed to them is an uninitialized scalar variable. This
635 allows the constructs such as C<open(my $fh, ...)> and C<open(local $fh,...)>
636 to be used to create filehandles that will conveniently be closed
637 automatically when the scope ends, provided there are no other references
638 to them. This largely eliminates the need for typeglobs when opening
639 filehandles that must be passed around, as in the following example:
643 or die "Can't open '@_': $!";
648 my $f = myopen("</etc/motd");
650 # $f implicitly closed here
653 =head2 open() with more than two arguments
655 If open() is passed three arguments instead of two, the second arguments
656 is used as the mode and the third argument is taken to be the file name.
657 This is primarily useful for protecting against unintended magic behavior
658 of the traditional two-argument form. See L<perlfunc/open>.
660 =head2 64-bit support
662 NOTE: The Configure flags -Duselonglong and -Duse64bits have been
663 deprecated. Use -Duse64bitint instead.
665 Any platform that has 64-bit integers either
667 (1) natively as longs or ints
668 (2) via special compiler flags
669 (3) using long long or int64_t
671 are able to use "quads" (64-bit integers) as follows:
677 constants (decimal, hexadecimal, octal, binary) in the code
681 arguments to oct() and hex()
685 arguments to print(), printf() and sprintf() (flag prefixes ll, L, q)
693 pack() and unpack() "q" and "Q" formats
697 in basic arithmetics: + - * / % (NOTE: operating close to the limits
698 of the integer values may produce surprising results)
702 in bit arithmetics: & | ^ ~ << >> (NOTE: these used to be forced
703 to be 32 bits wide but now operate on the full native width.)
711 Note that unless you have the case (a) you will have to configure
712 and compile Perl using the -Duse64bitint Configure flag.
714 There are actually two modes of 64-bitness: the first one is achieved
715 using Configure -Duse64bitint and the second one using Configure
716 -Duse64bitall. The difference is that the first one is minimal and
717 the second one maximal.
719 The C<use64bitint> does only as much as is required to get 64-bit
720 integers into Perl (this may mean, for example, using "long longs")
721 while your memory may still be limited to 2 gigabytes (because your
722 pointers could still be 32-bit). Note that the name C<64bitint> does
723 not imply that your C compiler will be using 64-bit C<int>s (it might,
724 but it doesn't have to): the C<use64bitint> means that you will be
725 able to have 64 bits wide scalar values.
727 The C<use64bitall> goes all the way by attempting to switch also
728 integers (if it can), longs (and pointers) to being 64-bit. This may
729 create an even more binary incompatible Perl than -Duse64bitint: the
730 resulting executable may not run at all in a 32-bit box, or you may
731 have to reboot/reconfigure/rebuild your operating system to be 64-bit
734 Natively 64-bit systems like Alpha and Cray need neither -Duse64bitint
737 Last but not least: note that due to Perl's habit of always using
738 floating point numbers, the quads are still not true integers.
739 When quads overflow their limits (0...18_446_744_073_709_551_615 unsigned,
740 -9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they
741 are silently promoted to floating point numbers, after which they will
742 start losing precision (in their lower digits).
744 =head2 Large file support
746 If you have filesystems that support "large files" (files larger than
747 2 gigabytes), you may now also be able to create and access them from
748 Perl. NOTE: the default action is to use the large file support, if
749 available on the platform.
751 If the large file support is on, and you have a Fcntl constant
752 O_LARGEFILE, the O_LARGEFILE is automatically added to the flags
755 Beware: unless your filesystem also supports "sparse files" seeking to
756 umpteen petabytes may be unadvisable.
758 Note that in addition to requiring a proper file system to do large
759 files you may also need to adjust your per-process (or your
760 per-system, or per-process-group, or per-user-group) maximum filesize
761 limits before running Perl scripts that try to handle large files,
762 especially if you intend to write such files.
764 Finally, in addition to your process/process group maximum filesize
765 limits, you may have quota limits on your filesystems that stop you
766 (your user id or your user group id) from using large files.
768 Adjusting your process/user/group/file system/operating system limits
769 is outside the scope of Perl core language. For process limits, you
770 may try increasing the limits using your shell's limits/limit/ulimit
771 command before running Perl. The BSD::Resource extension (not
772 included with the standard Perl distribution) may also be of use, it
773 offers the getrlimit/setrlimit interface that can be used to adjust
774 process resource usage limits, including the maximum filesize limit.
778 In some systems you may be able to use long doubles to enhance the
779 range and precision of your double precision floating point numbers
780 (that is, Perl's numbers). Use Configure -Duselongdouble to enable
781 this support (if it is available).
785 You can "Configure -Dusemorebits" to turn on both the 64-bit support
786 and the long double support.
788 =head2 Enhanced support for sort() subroutines
790 Perl subroutines with a prototype of C<($$)>, and XSUBs in general, can
791 now be used as sort subroutines. In either case, the two elements to
792 be compared are passed as normal parameters in @_. See L<perlfunc/sort>.
794 For unprototyped sort subroutines, the historical behavior of passing
795 the elements to be compared as the global variables $a and $b remains
798 =head2 Better syntax checks on parenthesized unary operators
802 print defined(&foo,&bar,&baz);
803 print uc("foo","bar","baz");
806 used to be accidentally allowed in earlier versions, and produced
807 unpredictable behaviour. Some produced ancillary warnings
808 when used in this way; others silently did the wrong thing.
810 The parenthesized forms of most unary operators that expect a single
811 argument now ensure that they are not called with more than one
812 argument, making the cases shown above syntax errors. The usual
815 print defined &foo, &bar, &baz;
816 print uc "foo", "bar", "baz";
819 remains unchanged. See L<perlop>.
821 =head2 POSIX character class syntax [: :] supported
823 For example to match alphabetic characters use /[[:alpha:]]/.
824 See L<perlre> for details.
826 =head2 Improved C<qw//> operator
828 The C<qw//> operator is now evaluated at compile time into a true list
829 instead of being replaced with a run time call to C<split()>. This
830 removes the confusing misbehaviour of C<qw//> in scalar context, which
831 had inherited that behaviour from split().
835 $foo = ($bar) = qw(a b c); print "$foo|$bar\n";
837 now correctly prints "3|a", instead of "2|a".
839 =head2 pack() format 'Z' supported
841 The new format type 'Z' is useful for packing and unpacking null-terminated
842 strings. See L<perlfunc/"pack">.
844 =head2 pack() format modifier '!' supported
846 The new format type modifier '!' is useful for packing and unpacking
847 native shorts, ints, and longs. See L<perlfunc/"pack">.
849 =head2 pack() and unpack() support counted strings
851 The template character '/' can be used to specify a counted string
852 type to be packed or unpacked. See L<perlfunc/"pack">.
854 =head2 Comments in pack() templates
856 The '#' character in a template introduces a comment up to
857 end of the line. This facilitates documentation of pack()
860 =head2 $^X variables may now have names longer than one character
862 Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax
863 error. Now variable names that begin with a control character may be
864 arbitrarily long. However, for compatibility reasons, these variables
865 I<must> be written with explicit braces, as C<${^XY}> for example.
866 C<${^XYZ}> is synonymous with ${"\cXYZ"}. Variable names with more
867 than one control character, such as C<${^XY^Z}>, are illegal.
869 The old syntax has not changed. As before, `^X' may be either a
870 literal control-X character or the two-character sequence `caret' plus
871 `X'. When braces are omitted, the variable name stops after the
872 control character. Thus C<"$^XYZ"> continues to be synonymous with
873 C<$^X . "YZ"> as before.
875 As before, lexical variables may not have names beginning with control
876 characters. As before, variables whose names begin with a control
877 character are always forced to be in package `main'. All such variables
878 are reserved for future extensions, except those that begin with
879 C<^_>, which may be used by user programs and are guaranteed not to
880 acquire special meaning in any future version of Perl.
882 =head2 C<use attrs> implicit in subroutine attributes
884 Formerly, if you wanted to mark a subroutine as being a method call or
885 as requiring an automatic lock() when it is entered, you had to declare
886 that with a C<use attrs> pragma in the body of the subroutine.
887 That can now be accomplished with declaration syntax, like this:
889 sub mymethod : locked method ;
891 sub mymethod : locked method {
895 sub othermethod :locked :method ;
897 sub othermethod :locked :method {
902 (Note how only the first C<:> is mandatory, and whitespace surrounding
903 the C<:> is optional.)
905 F<AutoSplit.pm> and F<SelfLoader.pm> have been updated to keep the attributes
906 with the stubs they provide. See L<attributes>.
908 =head2 Support for interpolating named characters
910 The new C<\N> escape interpolates named characters within strings.
911 For example, C<"Hi! \N{WHITE SMILING FACE}"> evaluates to a string
912 with a unicode smiley face at the end.
914 =head2 C<require> and C<do> may be overridden
916 C<require> and C<do 'file'> operations may be overridden locally
917 by importing subroutines of the same name into the current package
918 (or globally by importing them into the CORE::GLOBAL:: namespace).
919 Overriding C<require> will also affect C<use>, provided the override
920 is visible at compile-time.
921 See L<perlsub/"Overriding Built-in Functions">.
923 =head2 New variable $^C reflects C<-c> switch
925 C<$^C> has a boolean value that reflects whether perl is being run
926 in compile-only mode (i.e. via the C<-c> switch). Since
927 BEGIN blocks are executed under such conditions, this variable
928 enables perl code to determine whether actions that make sense
929 only during normal running are warranted. See L<perlvar>.
931 =head2 New variable $^V contains Perl version as a string
933 C<$^V> contains the Perl version number as a string composed of
934 characters whose ordinals match the version numbers, i.e. v5.6.0.
935 This may be used in string comparisons.
937 See C<Support for strings represented as a vector of ordinals> for an
940 =head2 Optional Y2K warnings
942 If Perl is built with the cpp macro C<PERL_Y2KWARN> defined,
943 it emits optional warnings when concatenating the number 19
946 This behavior must be specifically enabled when running Configure.
947 See F<INSTALL> and F<README.Y2K>.
949 =head1 Significant bug fixes
951 =head2 <HANDLE> on empty files
953 With C<$/> set to C<undef>, "slurping" an empty file returns a string of
954 zero length (instead of C<undef>, as it used to) the first time the
955 HANDLE is read after C<$/> is set to C<undef>. Further reads yield
958 This means that the following will append "foo" to an empty file (it used
961 perl -0777 -pi -e 's/^/foo/' empty_file
965 perl -pi -e 's/^/foo/' empty_file
967 is unchanged (it continues to leave the file empty).
969 =head2 C<eval '...'> improvements
971 Line numbers (as reflected by caller() and most diagnostics) within
972 C<eval '...'> were often incorrect where here documents were involved.
973 This has been corrected.
975 Lexical lookups for variables appearing in C<eval '...'> within
976 functions that were themselves called within an C<eval '...'> were
977 searching the wrong place for lexicals. The lexical search now
978 correctly ends at the subroutine's block boundary.
980 Parsing of here documents used to be flawed when they appeared as
981 the replacement expression in C<eval 's/.../.../e'>. This has
984 =head2 All compilation errors are true errors
986 Some "errors" encountered at compile time were by neccessity
987 generated as warnings followed by eventual termination of the
988 program. This enabled more such errors to be reported in a
989 single run, rather than causing a hard stop at the first error
990 that was encountered.
992 The mechanism for reporting such errors has been reimplemented
993 to queue compile-time errors and report them at the end of the
994 compilation as true errors rather than as warnings. This fixes
995 cases where error messages leaked through in the form of warnings
996 when code was compiled at run time using C<eval STRING>, and
997 also allows such errors to be reliably trapped using C<eval "...">.
999 =head2 Automatic flushing of output buffers
1001 fork(), exec(), system(), qx//, and pipe open()s now flush buffers
1002 of all files opened for output when the operation was attempted. This
1003 mostly eliminates confusing buffering mishaps suffered by users unaware
1004 of how Perl internally handles I/O.
1006 This is not supported on some platforms like Solaris where a suitably
1007 correct implementation of fflush(NULL) isn't available.
1009 =head2 Better diagnostics on meaningless filehandle operations
1011 Constructs such as C<< open(<FH>) >> and C<< close(<FH>) >>
1012 are compile time errors. Attempting to read from filehandles that
1013 were opened only for writing will now produce warnings (just as
1014 writing to read-only filehandles does).
1016 =head2 Where possible, buffered data discarded from duped input filehandle
1018 C<< open(NEW, "<&OLD") >> now attempts to discard any data that
1019 was previously read and buffered in C<OLD> before duping the handle.
1020 On platforms where doing this is allowed, the next read operation
1021 on C<NEW> will return the same data as the corresponding operation
1022 on C<OLD>. Formerly, it would have returned the data from the start
1023 of the following disk block instead.
1025 =head2 eof() has the same old magic as <>
1027 C<eof()> would return true if no attempt to read from C<< <> >> had
1028 yet been made. C<eof()> has been changed to have a little magic of its
1029 own, it now opens the C<< <> >> files.
1031 =head2 system(), backticks and pipe open now reflect exec() failure
1033 On Unix and similar platforms, system(), qx() and open(FOO, "cmd |")
1034 etc., are implemented via fork() and exec(). When the underlying
1035 exec() fails, earlier versions did not report the error properly,
1036 since the exec() happened to be in a different process.
1038 The child process now communicates with the parent about the
1039 error in launching the external command, which allows these
1040 constructs to return with their usual error value and set $!.
1042 =head2 Implicitly closed filehandles are safer
1044 Sometimes implicitly closed filehandles (as when they are localized,
1045 and Perl automatically closes them on exiting the scope) could
1046 inadvertently set $? or $!. This has been corrected.
1048 =head2 C<(\$)> prototype and C<$foo{a}>
1050 A scalar reference prototype now correctly allows a hash or
1051 array element in that slot.
1053 =head2 Pseudo-hashes work better
1055 Dereferencing some types of reference values in a pseudo-hash,
1056 such as C<< $ph->{foo}[1] >>, was accidentally disallowed. This has
1059 When applied to a pseudo-hash element, exists() now reports whether
1060 the specified value exists, not merely if the key is valid.
1062 delete() now works on pseudo-hashes. When given a pseudo-hash element
1063 or slice it deletes the values corresponding to the keys (but not the keys
1064 themselves). See L<perlref/"Pseudo-hashes: Using an array as a hash">.
1066 Pseudo-hash slices with constant keys are now optimized to array lookups
1069 The C<fields> pragma now provides ways to create pseudo-hashes, via
1070 fields::new() and fields::phash(). See L<fields>.
1072 =head2 C<goto &sub> and AUTOLOAD
1074 The C<goto &sub> construct works correctly when C<&sub> happens
1077 =head2 C<-bareword> allowed under C<use integer>
1079 The autoquoting of barewords preceded by C<-> did not work
1080 in prior versions when the C<integer> pragma was enabled.
1081 This has been fixed.
1083 =head2 Boolean assignment operators are legal lvalues
1085 Constructs such as C<($a ||= 2) += 1> are now allowed.
1087 =head2 C<sort $coderef @foo> allowed
1089 sort() did not accept a subroutine reference as the comparison
1090 function in earlier versions. This is now permitted.
1092 =head2 Failures in DESTROY()
1094 When code in a destructor threw an exception, it went unnoticed
1095 in earlier versions of Perl, unless someone happened to be
1096 looking in $@ just after the point the destructor happened to
1097 run. Such failures are now visible as warnings when warnings are
1100 =head2 Locale bugs fixed
1102 printf() and sprintf() previously reset the numeric locale
1103 back to the default "C" locale. This has been fixed.
1105 Numbers formatted according to the local numeric locale
1106 (such as using a decimal comma instead of a decimal dot) caused
1107 "isn't numeric" warnings, even while the operations accessing
1108 those numbers produced correct results. These warnings have been
1113 The C<eval 'return sub {...}'> construct could sometimes leak
1114 memory. This has been fixed.
1116 Operations that aren't filehandle constructors used to leak memory
1117 when used on invalid filehandles. This has been fixed.
1119 Constructs that modified C<@_> could fail to deallocate values
1120 in C<@_> and thus leak memory. This has been corrected.
1122 =head2 Spurious subroutine stubs after failed subroutine calls
1124 Perl could sometimes create empty subroutine stubs when a
1125 subroutine was not found in the package. Such cases stopped
1126 later method lookups from progressing into base packages.
1127 This has been corrected.
1129 =head2 Taint failures under C<-U>
1131 When running in unsafe mode, taint violations could sometimes
1132 cause silent failures. This has been fixed.
1134 =head2 END blocks and the C<-c> switch
1136 Prior versions used to run BEGIN B<and> END blocks when Perl was
1137 run in compile-only mode. Since this is typically not the expected
1138 behavior, END blocks are not executed anymore when the C<-c> switch
1141 See L<CHECK blocks> for how to run things when the compile phase ends.
1143 =head2 Potential to leak DATA filehandles
1145 Using the C<__DATA__> token creates an implicit filehandle to
1146 the file that contains the token. It is the program's
1147 responsibility to close it when it is done reading from it.
1149 This caveat is now better explained in the documentation.
1152 =head2 Diagnostics follow STDERR
1154 Diagnostic output now goes to whichever file the C<STDERR> handle
1155 is pointing at, instead of always going to the underlying C runtime
1156 library's C<stderr>.
1158 =head2 Other fixes for better diagnostics
1160 Line numbers are no longer suppressed (under most likely circumstances)
1161 during the global destruction phase.
1163 Diagnostics emitted from code running in threads other than the main
1164 thread are now accompanied by the thread ID.
1166 Embedded null characters in diagnostics now actually show up. They
1167 used to truncate the message in prior versions.
1169 $foo::a and $foo::b are now exempt from "possible typo" warnings only
1170 if sort() is encountered in package C<foo>.
1172 Unrecognized alphabetic escapes encountered when parsing quote
1173 constructs now generate a warning, since they may take on new
1174 semantics in later versions of Perl.
1176 Many diagnostics now report the internal operation in which the warning
1177 was provoked, like so:
1179 Use of uninitialized value in concatenation (.) at (eval 1) line 1.
1180 Use of uninitialized value in print at (eval 1) line 1.
1182 Diagnostics that occur within eval may also report the file and line
1183 number where the eval is located, in addition to the eval sequence
1184 number and the line number within the evaluated text itself. For
1187 Not enough arguments for scalar at (eval 4)[newlib/perl5db.pl:1411] line 2, at EOF
1189 =head1 Performance enhancements
1191 =head2 Simple sort() using { $a <=> $b } and the like are optimized
1193 Many common sort() operations using a simple inlined block are now
1194 optimized for faster performance.
1196 =head2 Optimized assignments to lexical variables
1198 Certain operations in the RHS of assignment statements have been
1199 optimized to directly set the lexical variable on the LHS,
1200 eliminating redundant copying overheads.
1202 =head2 Faster subroutine calls
1204 Minor changes in how subroutine calls are handled internally
1205 provide marginal improvements in performance.
1207 =head1 Platform specific changes
1209 =head2 Supported platforms
1215 VM/ESA is now supported.
1219 Siemens BS2000 is now supported under the POSIX Shell.
1223 The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread
1228 GNU/Hurd is now supported.
1232 Rhapsody/Darwin is now supported.
1236 EPOC is is now supported (on Psion 5).
1246 Perl now works with djgpp 2.02 (and 2.03 alpha).
1250 Environment variable names are not converted to uppercase any more.
1254 Incorrect exit codes from backticks have been fixed.
1258 This port continues to use its own builtin globbing (not File::Glob).
1262 =head2 OS390 (OpenEdition MVS)
1264 Support for this EBCDIC platform has not been renewed in this release.
1265 There are difficulties in reconciling Perl's standardization on UTF-8
1266 as its internal representation for characters with the EBCDIC character
1267 set, because the two are incompatible.
1269 It is unclear whether future versions will renew support for this
1270 platform, but the possibility exists.
1274 Numerous revisions and extensions to configuration, build, testing, and
1275 installation process to accomodate core changes and VMS-specific options.
1277 Expand %ENV-handling code to allow runtime mapping to logical names,
1278 CLI symbols, and CRTL environ array.
1280 Extension of subprocess invocation code to accept filespecs as command
1283 Add to Perl command line processing the ability to use default file types and
1284 to recognize Unix-style C<2E<gt>&1>.
1286 Expansion of File::Spec::VMS routines, and integration into ExtUtils::MM_VMS.
1288 Extension of ExtUtils::MM_VMS to handle complex extensions more flexibly.
1290 Barewords at start of Unix-syntax paths may be treated as text rather than
1291 only as logical names.
1293 Optional secure translation of several logical names used internally by Perl.
1295 Miscellaneous bugfixing and porting of new core code to VMS.
1297 Thanks are gladly extended to the many people who have contributed VMS
1298 patches, testing, and ideas.
1302 Perl can now emulate fork() internally, using multiple interpreters running
1303 in different concurrent threads. This support must be enabled at build
1304 time. See L<perlfork> for detailed information.
1306 When given a pathname that consists only of a drivename, such as C<A:>,
1307 opendir() and stat() now use the current working directory for the drive
1308 rather than the drive root.
1310 The builtin XSUB functions in the Win32:: namespace are documented. See
1313 $^X now contains the full path name of the running executable.
1315 A Win32::GetLongPathName() function is provided to complement
1316 Win32::GetFullPathName() and Win32::GetShortPathName(). See L<Win32>.
1318 POSIX::uname() is supported.
1320 system(1,...) now returns true process IDs rather than process
1321 handles. kill() accepts any real process id, rather than strictly
1322 return values from system(1,...).
1324 For better compatibility with Unix, C<kill(0, $pid)> can now be used to
1325 test whether a process exists.
1327 The C<Shell> module is supported.
1329 Better support for building Perl under command.com in Windows 95
1332 Scripts are read in binary mode by default to allow ByteLoader (and
1333 the filter mechanism in general) to work properly. For compatibility,
1334 the DATA filehandle will be set to text mode if a carriage return is
1335 detected at the end of the line containing the __END__ or __DATA__
1336 token; if not, the DATA filehandle will be left open in binary mode.
1337 Earlier versions always opened the DATA filehandle in text mode.
1339 The glob() operator is implemented via the C<File::Glob> extension,
1340 which supports glob syntax of the C shell. This increases the flexibility
1341 of the glob() operator, but there may be compatibility issues for
1342 programs that relied on the older globbing syntax. If you want to
1343 preserve compatibility with the older syntax, you might want to run
1344 perl with C<-MFile::DosGlob>. For details and compatibility information,
1353 Compatibility tests for C<sub : attrs> vs the older C<use attrs>.
1357 Tests for new environment scalar capability (e.g., C<use Env qw($BAR);>).
1361 Tests for new environment array capability (e.g., C<use Env qw(@PATH);>).
1365 IO constants (SEEK_*, _IO*).
1369 Directory-related IO methods (new, read, close, rewind, tied delete).
1371 =item lib/io_multihomed
1373 INET sockets with multi-homed hosts.
1385 Regression tests for C<my ($x,@y,%z) : attrs> and <sub : attrs>.
1389 File test operators.
1393 Verify operations that access pad objects (lexicals and temporaries).
1397 Verify C<exists &sub> operations.
1401 =head1 Modules and Pragmata
1409 While used internally by Perl as a pragma, this module also
1410 provides a way to fetch subroutine and variable attributes.
1415 WARNING: The Compiler suite remains highly experimental. The
1416 generated code may not be correct, even it manages to execute
1419 The Perl Compiler suite has been extensively reworked for this
1420 release. More of the standard Perl testsuite passes when run
1421 under the Compiler, but there is still a significant way to
1422 go to achieve production quality compiled executables.
1426 The ByteLoader is a dedicated extension to generate and run
1427 Perl bytecode. See L<ByteLoader>.
1431 References can now be used.
1433 The new version also allows a leading underscore in constant names, but
1434 disallows a double leading underscore (as in "__LINE__"). Some other names
1435 are disallowed or warned against, including BEGIN, END, etc. Some names
1436 which were forced into main:: used to fail silently in some cases; now they're
1437 fatal (outside of main::) and an optional warning (inside of main::).
1438 The ability to detect whether a constant had been set with a given name has
1445 This pragma implements the C<\N> string escape. See L<charnames>.
1449 A C<Maxdepth> setting can be specified to avoid venturing
1450 too deeply into deep data structures. See L<Data::Dumper>.
1452 The XSUB implementation of Dump() is now automatically called if the
1453 C<Useqq> setting is not in use.
1455 Dumping C<qr//> objects works correctly.
1459 C<DB> is an experimental module that exposes a clean abstraction
1460 to Perl's debugging API.
1464 DB_File can now be built with Berkeley DB versions 1, 2 or 3.
1465 See C<ext/DB_File/Changes>.
1469 Devel::DProf, a Perl source code profiler has been added. See
1470 L<Devel::DProf> and L<dprofpp>.
1474 The Dumpvalue module provides screen dumps of Perl data.
1478 Overall, Benchmark results exhibit lower average error and better timing
1481 You can now run tests for I<n> seconds instead of guessing the right
1482 number of tests to run: e.g., timethese(-5, ...) will run each
1483 code for at least 5 CPU seconds. Zero as the "number of repetitions"
1484 means "for at least 3 CPU seconds". The output format has also
1485 changed. For example:
1487 use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
1489 will now output something like this:
1491 Benchmark: running a, b, each for at least 5 CPU seconds...
1492 a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
1493 b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
1495 New features: "each for at least N CPU seconds...", "wallclock secs",
1496 and the "@ operations/CPU second (n=operations)".
1498 timethese() now returns a reference to a hash of Benchmark objects containing
1499 the test results, keyed on the names of the tests.
1501 timethis() now returns the iterations field in the Benchmark result object
1504 timethese(), timethis(), and the new cmpthese() (see below) can also take
1505 a format specifier of 'none' to suppress output.
1507 A new function countit() is just like timeit() except that it takes a
1508 TIME instead of a COUNT.
1510 A new function cmpthese() prints a chart comparing the results of each test
1511 returned from a timethese() call. For each possible pair of tests, the
1512 percentage speed difference (iters/sec or seconds/iter) is shown.
1514 For other details, see L<Benchmark>.
1518 The Devel::Peek module provides access to the internal representation
1519 of Perl variables and data. It is a data debugging tool for the XS programmer.
1523 $PERL_VERSION now stands for C<$^V> (a string value) rather than for C<$]>
1528 Env now supports accessing environment variables like PATH as array
1533 More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for
1534 large file (more than 4GB) access (NOTE: the O_LARGEFILE is
1535 automatically added to sysopen() flags if large file support has been
1536 configured, as is the default), Free/Net/OpenBSD locking behaviour
1537 flags F_FLOCK, F_POSIX, Linux F_SHLCK, and O_ACCMODE: the combined
1538 mask of O_RDONLY, O_WRONLY, and O_RDWR. The seek()/sysseek()
1539 constants SEEK_SET, SEEK_CUR, and SEEK_END are available via the
1540 C<:seek> tag. The chmod()/stat() S_IF* constants and S_IS* functions
1541 are available via the C<:mode> tag.
1545 A compare_text() function has been added, which allows custom
1546 comparison functions. See L<File::Compare>.
1550 File::Find now works correctly when the wanted() function is either
1551 autoloaded or is a symbolic reference.
1553 A bug that caused File::Find to lose track of the working directory
1554 when pruning top-level directories has been fixed.
1556 File::Find now also supports several other options to control its
1557 behavior. It can follow symbolic links if the C<follow> option is
1558 specified. Enabling the C<no_chdir> option will make File::Find skip
1559 changing the current directory when walking directories. The C<untaint>
1560 flag can be useful when running with taint checks enabled.
1566 This extension implements BSD-style file globbing. By default,
1567 it will also be used for the internal implementation of the glob()
1568 operator. See L<File::Glob>.
1572 New methods have been added to the File::Spec module: devnull() returns
1573 the name of the null device (/dev/null on Unix) and tmpdir() the name of
1574 the temp directory (normally /tmp on Unix). There are now also methods
1575 to convert between absolute and relative filenames: abs2rel() and
1576 rel2abs(). For compatibility with operating systems that specify volume
1577 names in file paths, the splitpath(), splitdir(), and catdir() methods
1580 =item File::Spec::Functions
1582 The new File::Spec::Functions modules provides a function interface
1583 to the File::Spec module. Allows shorthand
1585 $fullname = catfile($dir1, $dir2, $file);
1589 $fullname = File::Spec->catfile($dir1, $dir2, $file);
1593 Getopt::Long licensing has changed to allow the Perl Artistic License
1594 as well as the GPL. It used to be GPL only, which got in the way of
1595 non-GPL applications that wanted to use Getopt::Long.
1597 Getopt::Long encourages the use of Pod::Usage to produce help
1598 messages. For example:
1604 GetOptions('help|?' => \$help, man => \$man) or pod2usage(2);
1605 pod2usage(1) if $help;
1606 pod2usage(-exitstatus => 0, -verbose => 2) if $man;
1612 sample - Using GetOpt::Long and Pod::Usage
1616 sample [options] [file ...]
1619 -help brief help message
1620 -man full documentation
1628 Print a brief help message and exits.
1632 Prints the manual page and exits.
1638 B<This program> will read the given input file(s) and do someting
1639 useful with the contents thereof.
1643 See L<Pod::Usage> for details.
1645 A bug that prevented the non-option call-back <> from being
1646 specified as the first argument has been fixed.
1648 To specify the characters < and > as option starters, use ><. Note,
1649 however, that changing option starters is strongly deprecated.
1653 write() and syswrite() will now accept a single-argument
1654 form of the call, for consistency with Perl's syswrite().
1656 You can now create a TCP-based IO::Socket::INET without forcing
1657 a connect attempt. This allows you to configure its options
1658 (like making it non-blocking) and then call connect() manually.
1660 A bug that prevented the IO::Socket::protocol() accessor
1661 from ever returning the correct value has been corrected.
1663 IO::Socket::connect now uses non-blocking IO instead of alarm()
1664 to do connect timeouts.
1666 IO::Socket::accept now uses select() instead of alarm() for doing
1669 IO::Socket::INET->new now sets $! correctly on failure. $@ is
1670 still set for backwards compatability.
1674 Java Perl Lingo is now distributed with Perl. See jpl/README
1675 for more information.
1679 C<use lib> now weeds out any trailing duplicate entries.
1680 C<no lib> removes all named entries.
1684 The bitwise operations C<<< << >>>, C<<< >> >>>, C<&>, C<|>,
1685 and C<~> are now supported on bigints.
1689 The accessor methods Re, Im, arg, abs, rho, and theta can now also
1690 act as mutators (accessor $z->Re(), mutator $z->Re(3)).
1692 The class method C<display_format> and the corresponding object method
1693 C<display_format>, in addition to accepting just one argument, now can
1694 also accept a parameter hash. Recognized keys of a parameter hash are
1695 C<"style">, which corresponds to the old one parameter case, and two
1696 new parameters: C<"format">, which is a printf()-style format string
1697 (defaults usually to C<"%.15g">, you can revert to the default by
1698 setting the format string to C<undef>) used for both parts of a
1699 complex number, and C<"polar_pretty_print"> (defaults to true),
1700 which controls whether an attempt is made to try to recognize small
1701 multiples and rationals of pi (2pi, pi/2) at the argument (angle) of a
1702 polar complex number.
1704 The potentially disruptive change is that in list context both methods
1705 now I<return the parameter hash>, instead of only the value of the
1706 C<"style"> parameter.
1710 A little bit of radial trigonometry (cylindrical and spherical),
1711 radial coordinate conversions, and the great circle distance were added.
1713 =item Pod::Parser, Pod::InputObjects
1715 Pod::Parser is a base class for parsing and selecting sections of
1716 pod documentation from an input stream. This module takes care of
1717 identifying pod paragraphs and commands in the input and hands off the
1718 parsed paragraphs and commands to user-defined methods which are free
1719 to interpret or translate them as they see fit.
1721 Pod::InputObjects defines some input objects needed by Pod::Parser, and
1722 for advanced users of Pod::Parser that need more about a command besides
1725 As of release 5.6.0 of Perl, Pod::Parser is now the officially sanctioned
1726 "base parser code" recommended for use by all pod2xxx translators.
1727 Pod::Text (pod2text) and Pod::Man (pod2man) have already been converted
1728 to use Pod::Parser and efforts to convert Pod::HTML (pod2html) are already
1729 underway. For any questions or comments about pod parsing and translating
1730 issues and utilities, please use the pod-people@perl.org mailing list.
1732 For further information, please see L<Pod::Parser> and L<Pod::InputObjects>.
1734 =item Pod::Checker, podchecker
1736 This utility checks pod files for correct syntax, according to
1737 L<perlpod>. Obvious errors are flagged as such, while warnings are
1738 printed for mistakes that can be handled gracefully. The checklist is
1739 not complete yet. See L<Pod::Checker>.
1741 =item Pod::ParseUtils, Pod::Find
1743 These modules provide a set of gizmos that are useful mainly for pod
1744 translators. L<Pod::Find|Pod::Find> traverses directory structures and
1745 returns found pod files, along with their canonical names (like
1746 C<File::Spec::Unix>). L<Pod::ParseUtils|Pod::ParseUtils> contains
1747 B<Pod::List> (useful for storing pod list information), B<Pod::Hyperlink>
1748 (for parsing the contents of C<LE<lt>E<gt>> sequences) and B<Pod::Cache>
1749 (for caching information about pod files, e.g., link nodes).
1751 =item Pod::Select, podselect
1753 Pod::Select is a subclass of Pod::Parser which provides a function
1754 named "podselect()" to filter out user-specified sections of raw pod
1755 documentation from an input stream. podselect is a script that provides
1756 access to Pod::Select from other scripts to be used as a filter.
1759 =item Pod::Usage, pod2usage
1761 Pod::Usage provides the function "pod2usage()" to print usage messages for
1762 a Perl script based on its embedded pod documentation. The pod2usage()
1763 function is generally useful to all script authors since it lets them
1764 write and maintain a single source (the pods) for documentation, thus
1765 removing the need to create and maintain redundant usage message text
1766 consisting of information already in the pods.
1768 There is also a pod2usage script which can be used from other kinds of
1769 scripts to print usage messages from pods (even for non-Perl scripts
1770 with pods embedded in comments).
1772 For details and examples, please see L<Pod::Usage>.
1774 =item Pod::Text and Pod::Man
1776 Pod::Text has been rewritten to use Pod::Parser. While pod2text() is
1777 still available for backwards compatibility, the module now has a new
1778 preferred interface. See L<Pod::Text> for the details. The new Pod::Text
1779 module is easily subclassed for tweaks to the output, and two such
1780 subclasses (Pod::Text::Termcap for man-page-style bold and underlining
1781 using termcap information, and Pod::Text::Color for markup with ANSI color
1782 sequences) are now standard.
1784 pod2man has been turned into a module, Pod::Man, which also uses
1785 Pod::Parser. In the process, several outstanding bugs related to quotes
1786 in section headers, quoting of code escapes, and nested lists have been
1787 fixed. pod2man is now a wrapper script around this module.
1791 An EXISTS method has been added to this module (and sdbm_exists() has
1792 been added to the underlying sdbm library), so one can now call exists
1793 on an SDBM_File tied hash and get the correct result, rather than a
1796 A bug that may have caused data loss when more than one disk block
1797 happens to be read from the database in a single FETCH() has been
1802 Sys::Syslog now uses XSUBs to access facilities from syslog.h so it
1803 no longer requires syslog.ph to exist.
1807 Sys::Hostname now uses XSUBs to call the C library's gethostname() or
1808 uname() if they exist.
1810 =item Term::ANSIColor
1812 Term::ANSIColor is a very simple module to provide easy and readable
1813 access to the ANSI color and highlighting escape sequences, supported by
1814 most ANSI terminal emulators. It is now included standard.
1818 The timelocal() and timegm() functions used to silently return bogus
1819 results when the date fell outside the machine's integer range. They
1820 now consistently croak() if the date falls in an unsupported range.
1824 The error return value in list context has been changed for all functions
1825 that return a list of values. Previously these functions returned a list
1826 with a single element C<undef> if an error occurred. Now these functions
1827 return the empty list in these situations. This applies to the following
1833 The remaining functions are unchanged and continue to return C<undef> on
1834 error even in list context.
1836 The Win32::SetLastError(ERROR) function has been added as a complement
1837 to the Win32::GetLastError() function.
1839 The new Win32::GetFullPathName(FILENAME) returns the full absolute
1840 pathname for FILENAME in scalar context. In list context it returns
1841 a two-element list containing the fully qualified directory name and
1842 the filename. See L<Win32>.
1846 A new feature called "DBM Filters" has been added to all the
1847 DBM modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File.
1848 DBM Filters add four new methods to each DBM module:
1855 These can be used to filter key-value pairs before the pairs are
1856 written to the database or just after they are read from the database.
1857 See L<perldbmfilter> for further information.
1863 C<use attrs> is now obsolete, and is only provided for
1864 backward-compatibility. It's been replaced by the C<sub : attributes>
1865 syntax. See L<perlsub/"Subroutine Attributes"> and L<attributes>.
1867 Lexical warnings pragma, C<use warnings;>, to control optional warnings.
1870 C<use filetest> to control the behaviour of filetests (C<-r> C<-w>
1871 ...). Currently only one subpragma implemented, "use filetest
1872 'access';", that uses access(2) or equivalent to check permissions
1873 instead of using stat(2) as usual. This matters in filesystems
1874 where there are ACLs (access control lists): the stat(2) might lie,
1875 but access(2) knows better.
1877 =head1 Utility Changes
1881 C<perlcc> now supports the C and Bytecode backends. By default,
1882 it generates output from the simple C backend rather than the
1883 optimized C backend.
1885 Support for non-Unix platforms has been improved.
1889 C<perldoc> has been reworked to avoid possible security holes.
1890 It will not by default let itself be run as the superuser, but you
1891 may still use the B<-U> switch to try to make it drop privileges
1894 =head2 The Perl Debugger
1896 Many bug fixes and enhancements were added to F<perl5db.pl>, the
1897 Perl debugger. The help documentation was rearranged. New commands
1898 include C<< < ? >>, C<< > ? >>, and C<< { ? >> to list out current
1899 actions, C<man I<docpage>> to run your doc viewer on some perl
1900 docset, and support for quoted options. The help information was
1901 rearranged, and should be viewable once again if you're using B<less>
1902 as your pager. A serious security hole was plugged--you should
1903 immediately remove all older versions of the Perl debugger as
1904 installed in previous releases, all the way back to perl3, from
1905 your system to avoid being bitten by this.
1907 =head1 Documentation Changes
1913 The official list of public Perl API functions.
1915 =item perlcompile.pod
1917 An introduction to using the Perl Compiler suite.
1921 All material unrelated to running the Perl debugger, plus all
1922 low-level guts-like details that risked crushing the casual user
1923 of the debugger, have been relocated from the old manpage to the
1926 =item perldebguts.pod
1928 This new manpage contains excessively low-level material not related
1929 to the Perl debugger, but slightly related to debugging Perl itself.
1930 It also contains some arcane internal details of how the debugging
1931 process works that may only be of interest to developers of Perl
1934 =item perlfilter.pod
1936 An introduction to writing Perl source filters.
1940 Some guidelines for hacking the Perl source code.
1942 =item perlintern.pod
1944 A list of internal functions in the Perl source code.
1945 (List is currently empty.)
1947 =item perlopentut.pod
1949 A tutorial on using open() effectively.
1951 =item perlreftut.pod
1953 A tutorial that introduces the essentials of references.
1957 A tutorial for beginners on object-oriented Perl.
1961 A tutorial on managing class data for object modules.
1963 =item perlunicode.pod
1965 An introduction to Unicode support features in Perl.
1969 =head1 New or Changed Diagnostics
1973 =item "%s" variable %s masks earlier declaration in same %s
1975 (W) A "my" or "our" variable has been redeclared in the current scope or statement,
1976 effectively eliminating all access to the previous instance. This is almost
1977 always a typographical error. Note that the earlier variable will still exist
1978 until the end of the scope or until all closure referents to it are
1981 =item "my sub" not yet implemented
1983 (F) Lexically scoped subroutines are not yet implemented. Don't try that
1986 =item "our" variable %s redeclared
1988 (W) You seem to have already declared the same global once before in the
1989 current lexical scope.
1991 =item '!' allowed only after types %s
1993 (F) The '!' is allowed in pack() and unpack() only after certain types.
1994 See L<perlfunc/pack>.
1996 =item / cannot take a count
1998 (F) You had an unpack template indicating a counted-length string,
1999 but you have also specified an explicit size for the string.
2000 See L<perlfunc/pack>.
2002 =item / must be followed by a, A or Z
2004 (F) You had an unpack template indicating a counted-length string,
2005 which must be followed by one of the letters a, A or Z
2006 to indicate what sort of string is to be unpacked.
2007 See L<perlfunc/pack>.
2009 =item / must be followed by a*, A* or Z*
2011 (F) You had a pack template indicating a counted-length string,
2012 Currently the only things that can have their length counted are a*, A* or Z*.
2013 See L<perlfunc/pack>.
2015 =item / must follow a numeric type
2017 (F) You had an unpack template that contained a '#',
2018 but this did not follow some numeric unpack specification.
2019 See L<perlfunc/pack>.
2021 =item /%s/: Unrecognized escape \\%c passed through
2023 (W) You used a backslash-character combination which is not recognized
2024 by Perl. This combination appears in an interpolated variable or a
2025 C<'>-delimited regular expression. The character was understood literally.
2027 =item /%s/: Unrecognized escape \\%c in character class passed through
2029 (W) You used a backslash-character combination which is not recognized
2030 by Perl inside character classes. The character was understood literally.
2032 =item /%s/ should probably be written as "%s"
2034 (W) You have used a pattern where Perl expected to find a string,
2035 as in the first argument to C<join>. Perl will treat the true
2036 or false result of matching the pattern against $_ as the string,
2037 which is probably not what you had in mind.
2039 =item %s() called too early to check prototype
2041 (W) You've called a function that has a prototype before the parser saw a
2042 definition or declaration for it, and Perl could not check that the call
2043 conforms to the prototype. You need to either add an early prototype
2044 declaration for the subroutine in question, or move the subroutine
2045 definition ahead of the call to get proper prototype checking. Alternatively,
2046 if you are certain that you're calling the function correctly, you may put
2047 an ampersand before the name to avoid the warning. See L<perlsub>.
2049 =item %s argument is not a HASH or ARRAY element
2051 (F) The argument to exists() must be a hash or array element, such as:
2054 $ref->[12]->["susie"]
2056 =item %s argument is not a HASH or ARRAY element or slice
2058 (F) The argument to delete() must be either a hash or array element, such as:
2061 $ref->[12]->["susie"]
2063 or a hash or array slice, such as:
2065 @foo[$bar, $baz, $xyzzy]
2066 @{$ref->[12]}{"susie", "queue"}
2068 =item %s argument is not a subroutine name
2070 (F) The argument to exists() for C<exists &sub> must be a subroutine
2071 name, and not a subroutine call. C<exists &sub()> will generate this error.
2073 =item %s package attribute may clash with future reserved word: %s
2075 (W) A lowercase attribute name was used that had a package-specific handler.
2076 That name might have a meaning to Perl itself some day, even though it
2077 doesn't yet. Perhaps you should use a mixed-case attribute name, instead.
2080 =item (in cleanup) %s
2082 (W) This prefix usually indicates that a DESTROY() method raised
2083 the indicated exception. Since destructors are usually called by
2084 the system at arbitrary points during execution, and often a vast
2085 number of times, the warning is issued only once for any number
2086 of failures that would otherwise result in the same message being
2089 Failure of user callbacks dispatched using the C<G_KEEPERR> flag
2090 could also result in this warning. See L<perlcall/G_KEEPERR>.
2092 =item <> should be quotes
2094 (F) You wrote C<< require <file> >> when you should have written
2097 =item Attempt to join self
2099 (F) You tried to join a thread from within itself, which is an
2100 impossible task. You may be joining the wrong thread, or you may
2101 need to move the join() to some other thread.
2103 =item Bad evalled substitution pattern
2105 (F) You've used the /e switch to evaluate the replacement for a
2106 substitution, but perl found a syntax error in the code to evaluate,
2107 most likely an unexpected right brace '}'.
2109 =item Bad realloc() ignored
2111 (S) An internal routine called realloc() on something that had never been
2112 malloc()ed in the first place. Mandatory, but can be disabled by
2113 setting environment variable C<PERL_BADFREE> to 1.
2115 =item Bareword found in conditional
2117 (W) The compiler found a bareword where it expected a conditional,
2118 which often indicates that an || or && was parsed as part of the
2119 last argument of the previous construct, for example:
2123 It may also indicate a misspelled constant that has been interpreted
2126 use constant TYPO => 1;
2127 if (TYOP) { print "foo" }
2129 The C<strict> pragma is useful in avoiding such errors.
2131 =item Binary number > 0b11111111111111111111111111111111 non-portable
2133 (W) The binary number you specified is larger than 2**32-1
2134 (4294967295) and therefore non-portable between systems. See
2135 L<perlport> for more on portability concerns.
2137 =item Bit vector size > 32 non-portable
2139 (W) Using bit vector sizes larger than 32 is non-portable.
2141 =item Buffer overflow in prime_env_iter: %s
2143 (W) A warning peculiar to VMS. While Perl was preparing to iterate over
2144 %ENV, it encountered a logical name or symbol definition which was too long,
2145 so it was truncated to the string shown.
2147 =item Can't check filesystem of script "%s"
2149 (P) For some reason you can't check the filesystem of the script for nosuid.
2151 =item Can't declare class for non-scalar %s in "%s"
2153 (S) Currently, only scalar variables can declared with a specific class
2154 qualifier in a "my" or "our" declaration. The semantics may be extended
2155 for other types of variables in future.
2157 =item Can't declare %s in "%s"
2159 (F) Only scalar, array, and hash variables may be declared as "my" or
2160 "our" variables. They must have ordinary identifiers as names.
2162 =item Can't ignore signal CHLD, forcing to default
2164 (W) Perl has detected that it is being run with the SIGCHLD signal
2165 (sometimes known as SIGCLD) disabled. Since disabling this signal
2166 will interfere with proper determination of exit status of child
2167 processes, Perl has reset the signal to its default value.
2168 This situation typically indicates that the parent program under
2169 which Perl may be running (e.g., cron) is being very careless.
2171 =item Can't modify non-lvalue subroutine call
2173 (F) Subroutines meant to be used in lvalue context should be declared as
2174 such, see L<perlsub/"Lvalue subroutines">.
2176 =item Can't read CRTL environ
2178 (S) A warning peculiar to VMS. Perl tried to read an element of %ENV
2179 from the CRTL's internal environment array and discovered the array was
2180 missing. You need to figure out where your CRTL misplaced its environ
2181 or define F<PERL_ENV_TABLES> (see L<perlvms>) so that environ is not searched.
2183 =item Can't remove %s: %s, skipping file
2185 (S) You requested an inplace edit without creating a backup file. Perl
2186 was unable to remove the original file to replace it with the modified
2187 file. The file was left unmodified.
2189 =item Can't return %s from lvalue subroutine
2191 (F) Perl detected an attempt to return illegal lvalues (such
2192 as temporary or readonly values) from a subroutine used as an lvalue.
2193 This is not allowed.
2195 =item Can't weaken a nonreference
2197 (F) You attempted to weaken something that was not a reference. Only
2198 references can be weakened.
2200 =item Character class [:%s:] unknown
2202 (F) The class in the character class [: :] syntax is unknown.
2205 =item Character class syntax [%s] belongs inside character classes
2207 (W) The character class constructs [: :], [= =], and [. .] go
2208 I<inside> character classes, the [] are part of the construct,
2209 for example: /[012[:alpha:]345]/. Note that [= =] and [. .]
2210 are not currently implemented; they are simply placeholders for
2213 =item Constant is not %s reference
2215 (F) A constant value (perhaps declared using the C<use constant> pragma)
2216 is being dereferenced, but it amounts to the wrong type of reference. The
2217 message indicates the type of reference that was expected. This usually
2218 indicates a syntax error in dereferencing the constant value.
2219 See L<perlsub/"Constant Functions"> and L<constant>.
2221 =item constant(%s): %%^H is not localized
2223 (F) When setting compile-time-lexicalized hash %^H one should set the
2224 corresponding bit of $^H as well.
2226 =item constant(%s): %s
2228 (F) Compile-time-substitutions (such as overloaded constants and
2229 character names) were not correctly set up.
2231 =item CORE::%s is not a keyword
2233 (F) The CORE:: namespace is reserved for Perl keywords.
2235 =item defined(@array) is deprecated
2237 (D) defined() is not usually useful on arrays because it checks for an
2238 undefined I<scalar> value. If you want to see if the array is empty,
2239 just use C<if (@array) { # not empty }> for example.
2241 =item defined(%hash) is deprecated
2243 (D) defined() is not usually useful on hashes because it checks for an
2244 undefined I<scalar> value. If you want to see if the hash is empty,
2245 just use C<if (%hash) { # not empty }> for example.
2247 =item Did not produce a valid header
2251 =item Did you mean "local" instead of "our"?
2253 (W) Remember that "our" does not localize the declared global variable.
2254 You have declared it again in the same lexical scope, which seems superfluous.
2256 =item Document contains no data
2260 =item entering effective %s failed
2262 (F) While under the C<use filetest> pragma, switching the real and
2263 effective uids or gids failed.
2265 =item false [] range "%s" in regexp
2267 (W) A character class range must start and end at a literal character, not
2268 another character class like C<\d> or C<[:alpha:]>. The "-" in your false
2269 range is interpreted as a literal "-". Consider quoting the "-", "\-".
2272 =item Filehandle %s opened only for output
2274 (W) You tried to read from a filehandle opened only for writing. If you
2275 intended it to be a read/write filehandle, you needed to open it with
2276 "+<" or "+>" or "+>>" instead of with "<" or nothing. If
2277 you intended only to read from the file, use "<". See
2280 =item flock() on closed filehandle %s
2282 (W) The filehandle you're attempting to flock() got itself closed some
2283 time before now. Check your logic flow. flock() operates on filehandles.
2284 Are you attempting to call flock() on a dirhandle by the same name?
2286 =item Global symbol "%s" requires explicit package name
2288 (F) You've said "use strict vars", which indicates that all variables
2289 must either be lexically scoped (using "my"), declared beforehand using
2290 "our", or explicitly qualified to say which package the global variable
2293 =item Hexadecimal number > 0xffffffff non-portable
2295 (W) The hexadecimal number you specified is larger than 2**32-1
2296 (4294967295) and therefore non-portable between systems. See
2297 L<perlport> for more on portability concerns.
2299 =item Ill-formed CRTL environ value "%s"
2301 (W) A warning peculiar to VMS. Perl tried to read the CRTL's internal
2302 environ array, and encountered an element without the C<=> delimiter
2303 used to spearate keys from values. The element is ignored.
2305 =item Ill-formed message in prime_env_iter: |%s|
2307 (W) A warning peculiar to VMS. Perl tried to read a logical name
2308 or CLI symbol definition when preparing to iterate over %ENV, and
2309 didn't see the expected delimiter between key and value, so the
2312 =item Illegal binary digit %s
2314 (F) You used a digit other than 0 or 1 in a binary number.
2316 =item Illegal binary digit %s ignored
2318 (W) You may have tried to use a digit other than 0 or 1 in a binary number.
2319 Interpretation of the binary number stopped before the offending digit.
2321 =item Illegal number of bits in vec
2323 (F) The number of bits in vec() (the third argument) must be a power of
2324 two from 1 to 32 (or 64, if your platform supports that).
2326 =item Integer overflow in %s number
2328 (W) The hexadecimal, octal or binary number you have specified either
2329 as a literal or as an argument to hex() or oct() is too big for your
2330 architecture, and has been converted to a floating point number. On a
2331 32-bit architecture the largest hexadecimal, octal or binary number
2332 representable without overflow is 0xFFFFFFFF, 037777777777, or
2333 0b11111111111111111111111111111111 respectively. Note that Perl
2334 transparently promotes all numbers to a floating point representation
2335 internally--subject to loss of precision errors in subsequent
2338 =item Invalid %s attribute: %s
2340 The indicated attribute for a subroutine or variable was not recognized
2341 by Perl or by a user-supplied handler. See L<attributes>.
2343 =item Invalid %s attributes: %s
2345 The indicated attributes for a subroutine or variable were not recognized
2346 by Perl or by a user-supplied handler. See L<attributes>.
2348 =item invalid [] range "%s" in regexp
2350 The offending range is now explicitly displayed.
2352 =item Invalid separator character %s in attribute list
2354 (F) Something other than a colon or whitespace was seen between the
2355 elements of an attribute list. If the previous attribute
2356 had a parenthesised parameter list, perhaps that list was terminated
2357 too soon. See L<attributes>.
2359 =item Invalid separator character %s in subroutine attribute list
2361 (F) Something other than a colon or whitespace was seen between the
2362 elements of a subroutine attribute list. If the previous attribute
2363 had a parenthesised parameter list, perhaps that list was terminated
2366 =item leaving effective %s failed
2368 (F) While under the C<use filetest> pragma, switching the real and
2369 effective uids or gids failed.
2371 =item Lvalue subs returning %s not implemented yet
2373 (F) Due to limitations in the current implementation, array and hash
2374 values cannot be returned in subroutines used in lvalue context.
2375 See L<perlsub/"Lvalue subroutines">.
2377 =item Method %s not permitted
2381 =item Missing %sbrace%s on \N{}
2383 (F) Wrong syntax of character name literal C<\N{charname}> within
2384 double-quotish context.
2386 =item Missing command in piped open
2388 (W) You used the C<open(FH, "| command")> or C<open(FH, "command |")>
2389 construction, but the command was missing or blank.
2391 =item Missing name in "my sub"
2393 (F) The reserved syntax for lexically scoped subroutines requires that they
2394 have a name with which they can be found.
2396 =item No %s specified for -%c
2398 (F) The indicated command line switch needs a mandatory argument, but
2399 you haven't specified one.
2401 =item No package name allowed for variable %s in "our"
2403 (F) Fully qualified variable names are not allowed in "our" declarations,
2404 because that doesn't make much sense under existing semantics. Such
2405 syntax is reserved for future extensions.
2407 =item No space allowed after -%c
2409 (F) The argument to the indicated command line switch must follow immediately
2410 after the switch, without intervening spaces.
2412 =item no UTC offset information; assuming local time is UTC
2414 (S) A warning peculiar to VMS. Perl was unable to find the local
2415 timezone offset, so it's assuming that local system time is equivalent
2416 to UTC. If it's not, define the logical name F<SYS$TIMEZONE_DIFFERENTIAL>
2417 to translate to the number of seconds which need to be added to UTC to
2420 =item Octal number > 037777777777 non-portable
2422 (W) The octal number you specified is larger than 2**32-1 (4294967295)
2423 and therefore non-portable between systems. See L<perlport> for more
2424 on portability concerns.
2426 See also L<perlport> for writing portable code.
2428 =item panic: del_backref
2430 (P) Failed an internal consistency check while trying to reset a weak
2433 =item panic: kid popen errno read
2435 (F) forked child returned an incomprehensible message about its errno.
2437 =item panic: magic_killbackrefs
2439 (P) Failed an internal consistency check while trying to reset all weak
2440 references to an object.
2442 =item Parentheses missing around "%s" list
2444 (W) You said something like
2450 my ($foo, $bar) = @_;
2452 Remember that "my", "our", and "local" bind tighter than comma.
2454 =item Possible Y2K bug: %s
2456 (W) You are concatenating the number 19 with another number, which
2457 could be a potential Year 2000 problem.
2459 =item pragma "attrs" is deprecated, use "sub NAME : ATTRS" instead
2461 (W) You have written somehing like this:
2465 use attrs qw(locked);
2468 You should use the new declaration syntax instead.
2474 The C<use attrs> pragma is now obsolete, and is only provided for
2475 backward-compatibility. See L<perlsub/"Subroutine Attributes">.
2478 =item Premature end of script headers
2482 =item Repeat count in pack overflows
2484 (F) You can't specify a repeat count so large that it overflows
2485 your signed integers. See L<perlfunc/pack>.
2487 =item Repeat count in unpack overflows
2489 (F) You can't specify a repeat count so large that it overflows
2490 your signed integers. See L<perlfunc/unpack>.
2492 =item realloc() of freed memory ignored
2494 (S) An internal routine called realloc() on something that had already
2497 =item Reference is already weak
2499 (W) You have attempted to weaken a reference that is already weak.
2500 Doing so has no effect.
2502 =item setpgrp can't take arguments
2504 (F) Your system has the setpgrp() from BSD 4.2, which takes no arguments,
2505 unlike POSIX setpgid(), which takes a process ID and process group ID.
2507 =item Strange *+?{} on zero-length expression
2509 (W) You applied a regular expression quantifier in a place where it
2510 makes no sense, such as on a zero-width assertion.
2511 Try putting the quantifier inside the assertion instead. For example,
2512 the way to match "abc" provided that it is followed by three
2513 repetitions of "xyz" is C</abc(?=(?:xyz){3})/>, not C</abc(?=xyz){3}/>.
2515 =item switching effective %s is not implemented
2517 (F) While under the C<use filetest> pragma, we cannot switch the
2518 real and effective uids or gids.
2520 =item This Perl can't reset CRTL environ elements (%s)
2522 =item This Perl can't set CRTL environ elements (%s=%s)
2524 (W) Warnings peculiar to VMS. You tried to change or delete an element
2525 of the CRTL's internal environ array, but your copy of Perl wasn't
2526 built with a CRTL that contained the setenv() function. You'll need to
2527 rebuild Perl with a CRTL that does, or redefine F<PERL_ENV_TABLES> (see
2528 L<perlvms>) so that the environ array isn't the target of the change to
2529 %ENV which produced the warning.
2531 =item Unknown open() mode '%s'
2533 (F) The second argument of 3-argument open() is not among the list
2534 of valid modes: C<< < >>, C<< > >>, C<<< >> >>>, C<< +< >>,
2535 C<< +> >>, C<<< +>> >>>, C<-|>, C<|->.
2537 =item Unknown process %x sent message to prime_env_iter: %s
2539 (P) An error peculiar to VMS. Perl was reading values for %ENV before
2540 iterating over it, and someone else stuck a message in the stream of
2541 data Perl expected. Someone's very confused, or perhaps trying to
2542 subvert Perl's population of %ENV for nefarious purposes.
2544 =item Unrecognized escape \\%c passed through
2546 (W) You used a backslash-character combination which is not recognized
2547 by Perl. The character was understood literally.
2549 =item Unterminated attribute parameter in attribute list
2551 (F) The lexer saw an opening (left) parenthesis character while parsing an
2552 attribute list, but the matching closing (right) parenthesis
2553 character was not found. You may need to add (or remove) a backslash
2554 character to get your parentheses to balance. See L<attributes>.
2556 =item Unterminated attribute list
2558 (F) The lexer found something other than a simple identifier at the start
2559 of an attribute, and it wasn't a semicolon or the start of a
2560 block. Perhaps you terminated the parameter list of the previous attribute
2561 too soon. See L<attributes>.
2563 =item Unterminated attribute parameter in subroutine attribute list
2565 (F) The lexer saw an opening (left) parenthesis character while parsing a
2566 subroutine attribute list, but the matching closing (right) parenthesis
2567 character was not found. You may need to add (or remove) a backslash
2568 character to get your parentheses to balance.
2570 =item Unterminated subroutine attribute list
2572 (F) The lexer found something other than a simple identifier at the start
2573 of a subroutine attribute, and it wasn't a semicolon or the start of a
2574 block. Perhaps you terminated the parameter list of the previous attribute
2577 =item Value of CLI symbol "%s" too long
2579 (W) A warning peculiar to VMS. Perl tried to read the value of an %ENV
2580 element from a CLI symbol table, and found a resultant string longer
2581 than 1024 characters. The return value has been truncated to 1024
2584 =item Version number must be a constant number
2586 (P) The attempt to translate a C<use Module n.n LIST> statement into
2587 its equivalent C<BEGIN> block found an internal inconsistency with
2592 =head1 Obsolete Diagnostics
2596 =item Character class syntax [: :] is reserved for future extensions
2598 (W) Within regular expression character classes ([]) the syntax beginning
2599 with "[:" and ending with ":]" is reserved for future extensions.
2600 If you need to represent those character sequences inside a regular
2601 expression character class, just quote the square brackets with the
2602 backslash: "\[:" and ":\]".
2604 =item Ill-formed logical name |%s| in prime_env_iter
2606 (W) A warning peculiar to VMS. A logical name was encountered when preparing
2607 to iterate over %ENV which violates the syntactic rules governing logical
2608 names. Because it cannot be translated normally, it is skipped, and will not
2609 appear in %ENV. This may be a benign occurrence, as some software packages
2610 might directly modify logical name tables and introduce nonstandard names,
2611 or it may indicate that a logical name table has been corrupted.
2613 =item Probable precedence problem on %s
2615 (W) The compiler found a bareword where it expected a conditional,
2616 which often indicates that an || or && was parsed as part of the
2617 last argument of the previous construct, for example:
2621 =item regexp too big
2623 (F) The current implementation of regular expressions uses shorts as
2624 address offsets within a string. Unfortunately this means that if
2625 the regular expression compiles to longer than 32767, it'll blow up.
2626 Usually when you want a regular expression this big, there is a better
2627 way to do it with multiple statements. See L<perlre>.
2629 =item Use of "$$<digit>" to mean "${$}<digit>" is deprecated
2631 (D) Perl versions before 5.004 misinterpreted any type marker followed
2632 by "$" and a digit. For example, "$$0" was incorrectly taken to mean
2633 "${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004.
2635 However, the developers of Perl 5.004 could not fix this bug completely,
2636 because at least two widely-used modules depend on the old meaning of
2637 "$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the
2638 old (broken) way inside strings; but it generates this message as a
2639 warning. And in Perl 5.005, this special treatment will cease.
2643 =head1 Known Problems
2645 =head2 Thread tests failing
2647 The subtests 19 and 20 of the lib/thread test are known to fail in
2650 =head2 EBCDIC platforms not supported
2652 In earlier releases of Perl the EBCDIC environments like OS390 (also
2653 known as Open Edition MVS) and VM-ESA were supported. Due to the
2654 changes required by the UTF-8 (Unicode) support in Perl 5.6 the EBCDIC
2655 platforms are not supported in Perl 5.6.0.
2657 =head2 NEXTSTEP 3.3 POSIX test failure
2659 In NEXTSTEP 3.3p2 the implementation of the strftime(3) in the
2660 operating system libraries is buggy: the %j format numbers the days of
2661 a month starting from zero, which, while being logical to programmers,
2662 will cause the subtests 19 to 27 of the lib/posix test may fail.
2664 =head2 UNICOS/mk CC failures during Configure run
2666 In UNICOS/mk the following errors may appear during the Configure run:
2668 Guessing which symbols your C compiler and preprocessor define...
2669 CC-20 cc: ERROR File = try.c, Line = 3
2671 bad switch yylook 79bad switch yylook 79bad switch yylook 79bad switch yylook 79#ifdef A29K
2673 4 errors detected in the compilation of "try.c".
2675 The culprit is the broken awk of UNICOS/mk. The effect is fortunately
2676 rather mild: Perl itself is not adversely affected by the error, only
2677 the h2ph utility coming with Perl, and that is rather rarely needed
2680 =head2 Many features still experimental
2682 As discussed above, many features are still experimental, to a greater
2683 or lesser degree. Interfaces and implementation are subject to
2684 change, in extreme cases even subject to removal in some future
2685 release of Perl. These features include the following:
2693 =item Lvalue subroutines
2695 =item Weak references
2697 =item File globbing now implemented internally
2699 =item The Compiler suite
2703 =item the regular expression constructs C<(?{ code })> and C<(??{ code })>
2709 If you find what you think is a bug, you might check the
2710 articles recently posted to the comp.lang.perl.misc newsgroup.
2711 There may also be information at http://www.perl.com/perl/, the Perl
2714 If you believe you have an unreported bug, please run the B<perlbug>
2715 program included with your release. Be sure to trim your bug down
2716 to a tiny but sufficient test case. Your bug report, along with the
2717 output of C<perl -V>, will be sent off to perlbug@perl.com to be
2718 analysed by the Perl porting team.
2722 The F<Changes> file for exhaustive details on what changed.
2724 The F<INSTALL> file for how to build Perl.
2726 The F<README> file for general stuff.
2728 The F<Artistic> and F<Copying> files for copyright information.
2732 Written by Gurusamy Sarathy <F<gsar@activestate.com>>, with many
2733 contributions from The Perl Porters.
2735 Send omissions or corrections to <F<perlbug@perl.com>>.