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 More builtins taint their results
211 The C<passwd> and C<shell> fields returned by the getpwent(), getpwnam(),
212 and getpwuid() are now tainted, because the user can affect their own
213 encrypted password and login shell.
215 The variable modified by shmread(), and messages returned by msgrcv()
216 (and its object-oriented interface IPC::SysV::Msg::rcv) are also tainted,
217 because other untrusted processes can modify messages and shared memory
218 segments for their own nefarious purposes.
220 To avoid these new tainting behaviors, you can build Perl with the
221 Configure option C<-Accflags=-DINCOMPLETE_TAINTS>. Beware that the
222 ensuing perl binary may be insecure.
226 =head2 C Source Incompatibilities
230 =item C<PERL_POLLUTE>
232 Release 5.005 grandfathered old global symbol names by providing preprocessor
233 macros for extension source compatibility. As of release 5.6.0, these
234 preprocessor definitions are not available by default. You need to explicitly
235 compile perl with C<-DPERL_POLLUTE> to get these definitions. For
236 extensions still using the old symbols, this option can be
237 specified via MakeMaker:
239 perl Makefile.PL POLLUTE=1
241 =item C<PERL_IMPLICIT_CONTEXT>
243 NOTE: PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
244 with one of -Dusethreads, -Dusemultiplicity, or both. It is not
245 intended to be enabled by users at this time.
247 This new build option provides a set of macros for all API functions
248 such that an implicit interpreter/thread context argument is passed to
249 every API function. As a result of this, something like C<sv_setsv(foo,bar)>
250 amounts to a macro invocation that actually translates to something like
251 C<Perl_sv_setsv(my_perl,foo,bar)>. While this is generally expected
252 to not have any significant source compatibility issues, the difference
253 between a macro and a real function call will need to be considered.
255 This means that there B<is> a source compatibility issue as a result of
256 this if your extensions attempt to use pointers to any of the Perl API
259 Note that the above issue is not relevant to the default build of
260 Perl, whose interfaces continue to match those of prior versions
261 (but subject to the other options described here).
263 See L<perlguts/"The Perl API"> for detailed information on the
264 ramifications of building Perl with this option.
266 =item C<PERL_POLLUTE_MALLOC>
268 Enabling Perl's malloc in release 5.005 and earlier caused the namespace of
269 the system's malloc family of functions to be usurped by the Perl versions,
270 since by default they used the same names. Besides causing problems on
271 platforms that do not allow these functions to be cleanly replaced, this
272 also meant that the system versions could not be called in programs that
273 used Perl's malloc. Previous versions of Perl have allowed this behaviour
274 to be suppressed with the HIDEMYMALLOC and EMBEDMYMALLOC preprocessor
277 As of release 5.6.0, Perl's malloc family of functions have default names
278 distinct from the system versions. You need to explicitly compile perl with
279 C<-DPERL_POLLUTE_MALLOC> to get the older behaviour. HIDEMYMALLOC
280 and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now
283 Note that these functions do B<not> constitute Perl's memory allocation API.
284 See L<perlguts/"Memory Allocation"> for further information about that.
288 =head2 Compatible C Source API Changes
292 =item C<PATCHLEVEL> is now C<PERL_VERSION>
294 The cpp macros C<PERL_REVISION>, C<PERL_VERSION>, and C<PERL_SUBVERSION>
295 are now available by default from perl.h, and reflect the base revision,
296 patchlevel, and subversion respectively. C<PERL_REVISION> had no
297 prior equivalent, while C<PERL_VERSION> and C<PERL_SUBVERSION> were
298 previously available as C<PATCHLEVEL> and C<SUBVERSION>.
300 The new names cause less pollution of the B<cpp> namespace and reflect what
301 the numbers have come to stand for in common practice. For compatibility,
302 the old names are still supported when F<patchlevel.h> is explicitly
303 included (as required before), so there is no source incompatibility
308 =head2 Binary Incompatibilities
310 In general, the default build of this release is expected to be binary
311 compatible for extensions built with the 5.005 release or its maintenance
312 versions. However, specific platforms may have broken binary compatibility
313 due to changes in the defaults used in hints files. Therefore, please be
314 sure to always check the platform-specific README files for any notes to
317 The usethreads or usemultiplicity builds are B<not> binary compatible
318 with the corresponding builds in 5.005.
320 On platforms that require an explicit list of exports (AIX, OS/2 and Windows,
321 among others), purely internal symbols such as parser functions and the
322 run time opcodes are not exported by default. Perl 5.005 used to export
323 all functions irrespective of whether they were considered part of the
326 For the full list of public API functions, see L<perlapi>.
328 =head1 Installation and Configuration Improvements
330 =head2 -Dusethreads means something different
332 WARNING: Support for threads continues to be an experimental feature.
333 Interfaces and implementation are subject to sudden and drastic changes.
335 The -Dusethreads flag now enables the experimental interpreter-based thread
336 support by default. To get the flavor of experimental threads that was in
337 5.005 instead, you need to run Configure with "-Dusethreads -Duse5005threads".
339 As of v5.6.0, interpreter-threads support is still lacking a way to
340 create new threads from Perl (i.e., C<use Thread;> will not work with
341 interpreter threads). C<use Thread;> continues to be available when you
342 specify the -Duse5005threads option to Configure, bugs and all.
344 =head2 New Configure flags
346 The following new flags may be enabled on the Configure command line
347 by running Configure with C<-Dflag>.
350 usethreads useithreads (new interpreter threads: no Perl API yet)
351 usethreads use5005threads (threads as they were in 5.005)
353 use64bitint (equal to now deprecated 'use64bits')
359 usesocks (only SOCKS v5 supported)
361 =head2 Threadedness and 64-bitness now more daring
363 The Configure options enabling the use of threads and the use of
364 64-bitness are now more daring in the sense that they no more have an
365 explicit list of operating systems of known threads/64-bit
366 capabilities. In other words: if your operating system has the
367 necessary APIs and datatypes, you should be able just to go ahead and
368 use them, for threads by Configure -Dusethreads, and for 64 bits
369 either explicitly by Configure -Duse64bitint or implicitly if your
370 system has 64-bit wide datatypes. See also L<"64-bit support">.
374 Some platforms have "long doubles", floating point numbers of even
375 larger range than ordinary "doubles". To enable using long doubles for
376 Perl's scalars, use -Duselongdouble.
380 You can enable both -Duse64bitint and -Duselongdouble with -Dusemorebits.
381 See also L<"64-bit support">.
383 =head2 -Duselargefiles
385 Some platforms support system APIs that are capable of handling large files
386 (typically, files larger than two gigabytes). Perl will try to use these
387 APIs if you ask for -Duselargefiles.
389 See L<"Large file support"> for more information.
391 =head2 installusrbinperl
393 You can use "Configure -Uinstallusrbinperl" which causes installperl
394 to skip installing perl also as /usr/bin/perl. This is useful if you
395 prefer not to modify /usr/bin for some reason or another but harmful
396 because many scripts assume to find Perl in /usr/bin/perl.
400 You can use "Configure -Dusesocks" which causes Perl to probe
401 for the SOCKS proxy protocol library (v5, not v4). For more information
404 http://www.socks.nec.com/
408 You can "post-edit" the Configure variables using the Configure C<-A>
409 switch. The editing happens immediately after the platform specific
410 hints files have been processed but before the actual configuration
411 process starts. Run C<Configure -h> to find out the full C<-A> syntax.
413 =head2 Enhanced Installation Directories
415 The installation structure has been enriched to improve the support
416 for maintaining multiple versions of perl, to provide locations for
417 vendor-supplied modules, scripts, and manpages, and to ease maintenance
418 of locally-added modules, scripts, and manpages. See the section on
419 Installation Directories in the INSTALL file for complete details.
420 For most users building and installing from source, the defaults should
423 If you previously used C<Configure -Dsitelib> or C<-Dsitearch> to set
424 special values for library directories, you might wish to consider using
425 the new C<-Dsiteprefix> setting instead. Also, if you wish to re-use a
426 config.sh file from an earlier version of perl, you should be sure to
427 check that Configure makes sensible choices for the new directories.
428 See INSTALL for complete details.
432 =head2 Unicode and UTF-8 support
434 WARNING: This is an experimental feature. Implementation details are
437 Perl now uses UTF-8 as its internal representation for character
438 strings. The C<utf8> and C<bytes> pragmas are used to control this support
439 in the current lexical scope. See L<perlunicode>, L<utf8> and L<bytes> for
442 =head2 Interpreter cloning, threads, and concurrency
444 WARNING: This is an experimental feature. Implementation details are
447 Perl 5.005_63 introduces the beginnings of support for running multiple
448 interpreters concurrently in different threads. In conjunction with
449 the perl_clone() API call, which can be used to selectively duplicate
450 the state of any given interpreter, it is possible to compile a
451 piece of code once in an interpreter, clone that interpreter
452 one or more times, and run all the resulting interpreters in distinct
455 On Windows, this feature is used to emulate fork() at the interpreter
456 level. See L<perlfork>.
458 This feature is still in evolution. It is eventually meant to be used
459 to selectively clone a subroutine and data reachable from that
460 subroutine in a separate interpreter and run the cloned subroutine
461 in a separate thread. Since there is no shared data between the
462 interpreters, little or no locking will be needed (unless parts of
463 the symbol table are explicitly shared). This is obviously intended
464 to be an easy-to-use replacement for the existing threads support.
466 Support for cloning interpreters and interpreter concurrency can be
467 enabled using the -Dusethreads Configure option (see win32/Makefile for
468 how to enable it on Windows.) The resulting perl executable will be
469 functionally identical to one that was built with -Dmultiplicity, but
470 the perl_clone() API call will only be available in the former.
472 -Dusethreads enables the cpp macro USE_ITHREADS by default, which in turn
473 enables Perl source code changes that provide a clear separation between
474 the op tree and the data it operates with. The former is immutable, and
475 can therefore be shared between an interpreter and all of its clones,
476 while the latter is considered local to each interpreter, and is therefore
477 copied for each clone.
479 Note that building Perl with the -Dusemultiplicity Configure option
480 is adequate if you wish to run multiple B<independent> interpreters
481 concurrently in different threads. -Dusethreads only provides the
482 additional functionality of the perl_clone() API call and other
483 support for running B<cloned> interpreters concurrently.
485 =head2 Lexically scoped warning categories
487 You can now control the granularity of warnings emitted by perl at a finer
488 level using the C<use warnings> pragma. See L<warnings> and L<perllexwarn>
491 =head2 Lvalue subroutines
493 WARNING: This is an experimental feature. Details are subject to change.
495 Subroutines can now return modifiable lvalues.
496 See L<perlsub/"Lvalue subroutines">.
498 =head2 "our" declarations
500 An "our" declaration introduces a value that can be best understood
501 as a lexically scoped symbolic alias to a global variable in the
502 package that was current where the variable was declared. This is
503 mostly useful as an alternative to the C<vars> pragma, but also provides
504 the opportunity to introduce typing and other attributes for such
505 variables. See L<perlfunc/our>.
507 =head2 Support for strings represented as a vector of ordinals
509 Literals of the form C<v1.2.3.4> are now parsed as a string composed of
510 of characters with the specified ordinals. This is an alternative, more
511 readable way to construct (possibly unicode) strings instead of
512 interpolating characters, as in C<"\x{1}\x{2}\x{3}\x{4}">. The leading
513 C<v> may be omitted if there are more than two ordinals, so C<1.2.3> is
514 parsed the same as C<v1.2.3>.
516 Strings written in this form are also useful to represent version "numbers".
517 It is easy to compare such version "numbers" (which are really just plain
518 strings) using any of the usual string comparison operators C<eq>, C<ne>,
519 C<lt>, C<gt>, etc., or perform bitwise string operations on them using C<|>,
522 In conjunction with the new C<$^V> magic variable (which contains
523 the perl version as a string), such literals can be used as a readable way
524 to check if you're running a particular version of Perl:
526 # this will parse in older versions of Perl also
527 if ($^V and $^V gt v5.6.0) {
528 # new features supported
531 C<require> and C<use> also have some special magic to support such literals.
532 They will be interpreted as a version rather than as a module name:
534 require v5.6.0; # croak if $^V lt v5.6.0
535 use v5.6.0; # same, but croaks at compile-time
537 Alternatively, the C<v> may be omitted if there is more than one dot:
542 Also, C<sprintf> and C<printf> support the Perl-specific format flag C<%v>
543 to print ordinals of characters in arbitrary strings:
545 printf "v%vd", $^V; # prints current version, such as "v5.5.650"
546 printf "%*vX", ":", $addr; # formats IPv6 address
547 printf "%*vb", " ", $bits; # displays bitstring
549 See L<perldata/"Scalar value constructors"> for additional information.
551 =head2 Weak references
553 WARNING: This is an experimental feature. Details are subject to change.
555 In previous versions of Perl, you couldn't cache objects so as
556 to allow them to be deleted if the last reference from outside
557 the cache is deleted. The reference in the cache would hold a
558 reference count on the object and the objects would never be
561 Another familiar problem is with circular references. When an
562 object references itself, its reference count would never go
563 down to zero, and it would not get destroyed until the program
566 Weak references solve this by allowing you to "weaken" any
567 reference, that is, make it not count towards the reference count.
568 When the last non-weak reference to an object is deleted, the object
569 is destroyed and all the weak references to the object are
570 automatically undef-ed.
572 To use this feature, you need the WeakRef package from CPAN, which
573 contains additional documentation.
575 =head2 File globbing implemented internally
577 WARNING: This is currently an experimental feature. Interfaces and
578 implementation are likely to change.
580 Perl now uses the File::Glob implementation of the glob() operator
581 automatically. This avoids using an external csh process and the
582 problems associated with it.
584 =head2 Binary numbers supported
586 Binary numbers are now supported as literals, in s?printf formats, and
590 printf "The answer is: %b\n", oct("0b101010");
592 =head2 Some arrows may be omitted in calls through references
594 Perl now allows the arrow to be omitted in many constructs
595 involving subroutine calls through references. For example,
596 C<< $foo[10]->('foo') >> may now be written C<$foo[10]('foo')>.
597 This is rather similar to how the arrow may be omitted from
598 C<< $foo[10]->{'foo'} >>. Note however, that the arrow is still
599 required for C<< foo(10)->('bar') >>.
601 =head2 exists() is supported on subroutine names
603 The exists() builtin now works on subroutine names. A subroutine
604 is considered to exist if it has been declared (even if implicitly).
605 See L<perlfunc/exists> for examples.
607 =head2 exists() and delete() are supported on array elements
609 The exists() and delete() builtins now work on simple arrays as well.
610 The behavior is similar to that on hash elements.
612 exists() can be used to check whether an array element has been
613 initialized. This avoids autovivifying array elements that don't exist.
614 If the array is tied, the EXISTS() method in the corresponding tied
615 package will be invoked.
617 delete() may be used to remove an element from the array and return
618 it. The array element at that position returns to its unintialized
619 state, so that testing for the same element with exists() will return
620 false. If the element happens to be the one at the end, the size of
621 the array also shrinks up to the highest element that tests true for
622 exists(), or 0 if none such is found. If the array is tied, the DELETE()
623 method in the corresponding tied package will be invoked.
625 See L<perlfunc/exists> and L<perlfunc/delete> for examples.
627 =head2 syswrite() ease-of-use
629 The length argument of C<syswrite()> has become optional.
631 =head2 File and directory handles can be autovivified
633 Similar to how constructs such as C<< $x->[0] >> autovivify a reference,
634 handle constructors (open(), opendir(), pipe(), socketpair(), sysopen(),
635 socket(), and accept()) now autovivify a file or directory handle
636 if the handle passed to them is an uninitialized scalar variable. This
637 allows the constructs such as C<open(my $fh, ...)> and C<open(local $fh,...)>
638 to be used to create filehandles that will conveniently be closed
639 automatically when the scope ends, provided there are no other references
640 to them. This largely eliminates the need for typeglobs when opening
641 filehandles that must be passed around, as in the following example:
645 or die "Can't open '@_': $!";
650 my $f = myopen("</etc/motd");
652 # $f implicitly closed here
655 =head2 open() with more than two arguments
657 If open() is passed three arguments instead of two, the second arguments
658 is used as the mode and the third argument is taken to be the file name.
659 This is primarily useful for protecting against unintended magic behavior
660 of the traditional two-argument form. See L<perlfunc/open>.
662 =head2 64-bit support
664 WARNING: 64-bit support is still experimental on most platforms.
665 Existing support only covers the LP64 data model. In particular, the
666 LLP64 data model is not yet supported. 64-bit libraries and system
667 APIs on many platforms have not stabilized--your mileage may vary.
669 Any platform that has 64-bit integers either
671 (1) natively as longs or ints
672 (2) via special compiler flags
673 (3) using long long or int64_t
675 are able to use "quads" (64-bit integers) as follows:
677 NOTE: The Configure flags -Duselonglong and -Duse64bits have been
678 deprecated. Use -Duse64bitint instead.
684 constants (decimal, hexadecimal, octal, binary) in the code
688 arguments to oct() and hex()
692 arguments to print(), printf() and sprintf() (flag prefixes ll, L, q)
700 pack() and unpack() "q" and "Q" formats
704 in basic arithmetics: + - * / % (NOTE: operating close to the limits
705 of the integer values may produce surprising results)
709 in bit arithmetics: & | ^ ~ << >> (NOTE: these used to be forced
710 to be 32 bits wide but now operate on the full native width.)
718 Note that unless you have the case (a) you will have to configure
719 and compile Perl using the -Duse64bitint Configure flag.
721 There are actually two modes of 64-bitness: the first one is achieved
722 using Configure -Duse64bitint and the second one using Configure
723 -Duse64bitall. The difference is that the first one is minimal and
724 the second one maximal. The first works in more places than the second.
726 The C<use64bitint> does only as much as is required to get 64-bit
727 integers into Perl (this may mean, for example, using "long longs")
728 while your memory may still be limited to 2 gigabytes (because your
729 pointers could still be 32-bit). Note that the name C<64bitint> does
730 not imply that your C compiler will be using 64-bit C<int>s (it might,
731 but it doesn't have to): the C<use64bitint> means that you will be
732 able to have 64 bits wide scalar values.
734 The C<use64bitall> goes all the way by attempting to switch also
735 integers (if it can), longs (and pointers) to being 64-bit. This may
736 create an even more binary incompatible Perl than -Duse64bitint: the
737 resulting executable may not run at all in a 32-bit box, or you may
738 have to reboot/reconfigure/rebuild your operating system to be 64-bit
741 Natively 64-bit systems like Alpha and Cray need neither -Duse64bitint
744 Last but not least: note that due to Perl's habit of always using
745 floating point numbers, the quads are still not true integers.
746 When quads overflow their limits (0...18_446_744_073_709_551_615 unsigned,
747 -9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they
748 are silently promoted to floating point numbers, after which they will
749 start losing precision (in their lower digits).
751 =head2 Large file support
753 If you have filesystems that support "large files" (files larger than
754 2 gigabytes), you may now also be able to create and access them from
755 Perl. NOTE: the default action is to use the large file support, if
756 available on the platform.
758 If the large file support is on, and you have a Fcntl constant
759 O_LARGEFILE, the O_LARGEFILE is automatically added to the flags
762 Beware: unless your filesystem also supports "sparse files" seeking to
763 umpteen petabytes may be unadvisable.
765 Note that in addition to requiring a proper file system to do large
766 files you may also need to adjust your per-process (or your
767 per-system, or per-process-group, or per-user-group) maximum filesize
768 limits before running Perl scripts that try to handle large files,
769 especially if you intend to write such files.
771 Finally, in addition to your process/process group maximum filesize
772 limits, you may have quota limits on your filesystems that stop you
773 (your user id or your user group id) from using large files.
775 Adjusting your process/user/group/file system/operating system limits
776 is outside the scope of Perl core language. For process limits, you
777 may try increasing the limits using your shell's limits/limit/ulimit
778 command before running Perl. The BSD::Resource extension (not
779 included with the standard Perl distribution) may also be of use, it
780 offers the getrlimit/setrlimit interface that can be used to adjust
781 process resource usage limits, including the maximum filesize limit.
785 In some systems you may be able to use long doubles to enhance the
786 range and precision of your double precision floating point numbers
787 (that is, Perl's numbers). Use Configure -Duselongdouble to enable
788 this support (if it is available).
792 You can "Configure -Dusemorebits" to turn on both the 64-bit support
793 and the long double support.
795 =head2 Enhanced support for sort() subroutines
797 Perl subroutines with a prototype of C<($$)>, and XSUBs in general, can
798 now be used as sort subroutines. In either case, the two elements to
799 be compared are passed as normal parameters in @_. See L<perlfunc/sort>.
801 For unprototyped sort subroutines, the historical behavior of passing
802 the elements to be compared as the global variables $a and $b remains
805 =head2 Better syntax checks on parenthesized unary operators
809 print defined(&foo,&bar,&baz);
810 print uc("foo","bar","baz");
813 used to be accidentally allowed in earlier versions, and produced
814 unpredictable behaviour. Some produced ancillary warnings
815 when used in this way; others silently did the wrong thing.
817 The parenthesized forms of most unary operators that expect a single
818 argument now ensure that they are not called with more than one
819 argument, making the cases shown above syntax errors. The usual
822 print defined &foo, &bar, &baz;
823 print uc "foo", "bar", "baz";
826 remains unchanged. See L<perlop>.
828 =head2 POSIX character class syntax [: :] supported
830 For example to match alphabetic characters use /[[:alpha:]]/.
831 See L<perlre> for details.
833 =head2 Improved C<qw//> operator
835 The C<qw//> operator is now evaluated at compile time into a true list
836 instead of being replaced with a run time call to C<split()>. This
837 removes the confusing misbehaviour of C<qw//> in scalar context, which
838 had inherited that behaviour from split().
842 $foo = ($bar) = qw(a b c); print "$foo|$bar\n";
844 now correctly prints "3|a", instead of "2|a".
846 =head2 pack() format 'Z' supported
848 The new format type 'Z' is useful for packing and unpacking null-terminated
849 strings. See L<perlfunc/"pack">.
851 =head2 pack() format modifier '!' supported
853 The new format type modifier '!' is useful for packing and unpacking
854 native shorts, ints, and longs. See L<perlfunc/"pack">.
856 =head2 pack() and unpack() support counted strings
858 The template character '/' can be used to specify a counted string
859 type to be packed or unpacked. See L<perlfunc/"pack">.
861 =head2 Comments in pack() templates
863 The '#' character in a template introduces a comment up to
864 end of the line. This facilitates documentation of pack()
867 =head2 $^X variables may now have names longer than one character
869 Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax
870 error. Now variable names that begin with a control character may be
871 arbitrarily long. However, for compatibility reasons, these variables
872 I<must> be written with explicit braces, as C<${^XY}> for example.
873 C<${^XYZ}> is synonymous with ${"\cXYZ"}. Variable names with more
874 than one control character, such as C<${^XY^Z}>, are illegal.
876 The old syntax has not changed. As before, `^X' may be either a
877 literal control-X character or the two-character sequence `caret' plus
878 `X'. When braces are omitted, the variable name stops after the
879 control character. Thus C<"$^XYZ"> continues to be synonymous with
880 C<$^X . "YZ"> as before.
882 As before, lexical variables may not have names beginning with control
883 characters. As before, variables whose names begin with a control
884 character are always forced to be in package `main'. All such variables
885 are reserved for future extensions, except those that begin with
886 C<^_>, which may be used by user programs and are guaranteed not to
887 acquire special meaning in any future version of Perl.
889 =head2 C<use attrs> implicit in subroutine attributes
891 Formerly, if you wanted to mark a subroutine as being a method call or
892 as requiring an automatic lock() when it is entered, you had to declare
893 that with a C<use attrs> pragma in the body of the subroutine.
894 That can now be accomplished with declaration syntax, like this:
896 sub mymethod : locked method ;
898 sub mymethod : locked method {
902 sub othermethod :locked :method ;
904 sub othermethod :locked :method {
909 (Note how only the first C<:> is mandatory, and whitespace surrounding
910 the C<:> is optional.)
912 F<AutoSplit.pm> and F<SelfLoader.pm> have been updated to keep the attributes
913 with the stubs they provide. See L<attributes>.
915 =head2 Support for interpolating named characters
917 The new C<\N> escape interpolates named characters within strings.
918 For example, C<"Hi! \N{WHITE SMILING FACE}"> evaluates to a string
919 with a unicode smiley face at the end.
921 =head2 C<require> and C<do> may be overridden
923 C<require> and C<do 'file'> operations may be overridden locally
924 by importing subroutines of the same name into the current package
925 (or globally by importing them into the CORE::GLOBAL:: namespace).
926 Overriding C<require> will also affect C<use>, provided the override
927 is visible at compile-time.
928 See L<perlsub/"Overriding Built-in Functions">.
930 =head2 New variable $^C reflects C<-c> switch
932 C<$^C> has a boolean value that reflects whether perl is being run
933 in compile-only mode (i.e. via the C<-c> switch). Since
934 BEGIN blocks are executed under such conditions, this variable
935 enables perl code to determine whether actions that make sense
936 only during normal running are warranted. See L<perlvar>.
938 =head2 New variable $^V contains Perl version as a string
940 C<$^V> contains the Perl version number as a string composed of
941 characters whose ordinals match the version numbers, i.e. v5.6.0.
942 This may be used in string comparisons.
944 See C<Support for strings represented as a vector of ordinals> for an
947 =head2 Optional Y2K warnings
949 If Perl is built with the cpp macro C<PERL_Y2KWARN> defined,
950 it emits optional warnings when concatenating the number 19
953 This behavior must be specifically enabled when running Configure.
954 See F<INSTALL> and F<README.Y2K>.
956 =head1 Significant bug fixes
958 =head2 <HANDLE> on empty files
960 With C<$/> set to C<undef>, "slurping" an empty file returns a string of
961 zero length (instead of C<undef>, as it used to) the first time the
962 HANDLE is read after C<$/> is set to C<undef>. Further reads yield
965 This means that the following will append "foo" to an empty file (it used
968 perl -0777 -pi -e 's/^/foo/' empty_file
972 perl -pi -e 's/^/foo/' empty_file
974 is unchanged (it continues to leave the file empty).
976 =head2 C<eval '...'> improvements
978 Line numbers (as reflected by caller() and most diagnostics) within
979 C<eval '...'> were often incorrect where here documents were involved.
980 This has been corrected.
982 Lexical lookups for variables appearing in C<eval '...'> within
983 functions that were themselves called within an C<eval '...'> were
984 searching the wrong place for lexicals. The lexical search now
985 correctly ends at the subroutine's block boundary.
987 Parsing of here documents used to be flawed when they appeared as
988 the replacement expression in C<eval 's/.../.../e'>. This has
991 =head2 All compilation errors are true errors
993 Some "errors" encountered at compile time were by neccessity
994 generated as warnings followed by eventual termination of the
995 program. This enabled more such errors to be reported in a
996 single run, rather than causing a hard stop at the first error
997 that was encountered.
999 The mechanism for reporting such errors has been reimplemented
1000 to queue compile-time errors and report them at the end of the
1001 compilation as true errors rather than as warnings. This fixes
1002 cases where error messages leaked through in the form of warnings
1003 when code was compiled at run time using C<eval STRING>, and
1004 also allows such errors to be reliably trapped using C<eval "...">.
1006 =head2 Automatic flushing of output buffers
1008 fork(), exec(), system(), qx//, and pipe open()s now flush buffers
1009 of all files opened for output when the operation was attempted. This
1010 mostly eliminates confusing buffering mishaps suffered by users unaware
1011 of how Perl internally handles I/O.
1013 This is not supported on some platforms like Solaris where a suitably
1014 correct implementation of fflush(NULL) isn't available.
1016 =head2 Better diagnostics on meaningless filehandle operations
1018 Constructs such as C<< open(<FH>) >> and C<< close(<FH>) >>
1019 are compile time errors. Attempting to read from filehandles that
1020 were opened only for writing will now produce warnings (just as
1021 writing to read-only filehandles does).
1023 =head2 Where possible, buffered data discarded from duped input filehandle
1025 C<< open(NEW, "<&OLD") >> now attempts to discard any data that
1026 was previously read and buffered in C<OLD> before duping the handle.
1027 On platforms where doing this is allowed, the next read operation
1028 on C<NEW> will return the same data as the corresponding operation
1029 on C<OLD>. Formerly, it would have returned the data from the start
1030 of the following disk block instead.
1032 =head2 eof() has the same old magic as <>
1034 C<eof()> would return true if no attempt to read from C<< <> >> had
1035 yet been made. C<eof()> has been changed to have a little magic of its
1036 own, it now opens the C<< <> >> files.
1038 =head2 system(), backticks and pipe open now reflect exec() failure
1040 On Unix and similar platforms, system(), qx() and open(FOO, "cmd |")
1041 etc., are implemented via fork() and exec(). When the underlying
1042 exec() fails, earlier versions did not report the error properly,
1043 since the exec() happened to be in a different process.
1045 The child process now communicates with the parent about the
1046 error in launching the external command, which allows these
1047 constructs to return with their usual error value and set $!.
1049 =head2 Implicitly closed filehandles are safer
1051 Sometimes implicitly closed filehandles (as when they are localized,
1052 and Perl automatically closes them on exiting the scope) could
1053 inadvertently set $? or $!. This has been corrected.
1055 =head2 C<(\$)> prototype and C<$foo{a}>
1057 A scalar reference prototype now correctly allows a hash or
1058 array element in that slot.
1060 =head2 Pseudo-hashes work better
1062 WARNING: The pseudo-hash data type continues to be experimental.
1063 Limiting oneself to the interface elements provided by the
1064 fields pragma will provide protection from any future changes.
1066 Dereferencing some types of reference values in a pseudo-hash,
1067 such as C<< $ph->{foo}[1] >>, was accidentally disallowed. This has
1070 When applied to a pseudo-hash element, exists() now reports whether
1071 the specified value exists, not merely if the key is valid.
1073 delete() now works on pseudo-hashes. When given a pseudo-hash element
1074 or slice it deletes the values corresponding to the keys (but not the keys
1075 themselves). See L<perlref/"Pseudo-hashes: Using an array as a hash">.
1077 Pseudo-hash slices with constant keys are now optimized to array lookups
1080 The C<fields> pragma now provides ways to create pseudo-hashes, via
1081 fields::new() and fields::phash(). See L<fields>.
1083 =head2 C<goto &sub> and AUTOLOAD
1085 The C<goto &sub> construct works correctly when C<&sub> happens
1088 =head2 C<-bareword> allowed under C<use integer>
1090 The autoquoting of barewords preceded by C<-> did not work
1091 in prior versions when the C<integer> pragma was enabled.
1092 This has been fixed.
1094 =head2 Boolean assignment operators are legal lvalues
1096 Constructs such as C<($a ||= 2) += 1> are now allowed.
1098 =head2 C<sort $coderef @foo> allowed
1100 sort() did not accept a subroutine reference as the comparison
1101 function in earlier versions. This is now permitted.
1103 =head2 Failures in DESTROY()
1105 When code in a destructor threw an exception, it went unnoticed
1106 in earlier versions of Perl, unless someone happened to be
1107 looking in $@ just after the point the destructor happened to
1108 run. Such failures are now visible as warnings when warnings are
1111 =head2 Locale bugs fixed
1113 printf() and sprintf() previously reset the numeric locale
1114 back to the default "C" locale. This has been fixed.
1116 Numbers formatted according to the local numeric locale
1117 (such as using a decimal comma instead of a decimal dot) caused
1118 "isn't numeric" warnings, even while the operations accessing
1119 those numbers produced correct results. These warnings have been
1124 The C<eval 'return sub {...}'> construct could sometimes leak
1125 memory. This has been fixed.
1127 Operations that aren't filehandle constructors used to leak memory
1128 when used on invalid filehandles. This has been fixed.
1130 Constructs that modified C<@_> could fail to deallocate values
1131 in C<@_> and thus leak memory. This has been corrected.
1133 =head2 Spurious subroutine stubs after failed subroutine calls
1135 Perl could sometimes create empty subroutine stubs when a
1136 subroutine was not found in the package. Such cases stopped
1137 later method lookups from progressing into base packages.
1138 This has been corrected.
1140 =head2 Taint failures under C<-U>
1142 When running in unsafe mode, taint violations could sometimes
1143 cause silent failures. This has been fixed.
1145 =head2 END blocks and the C<-c> switch
1147 Prior versions used to run BEGIN B<and> END blocks when Perl was
1148 run in compile-only mode. Since this is typically not the expected
1149 behavior, END blocks are not executed anymore when the C<-c> switch
1152 See L<CHECK blocks> for how to run things when the compile phase ends.
1154 =head2 Potential to leak DATA filehandles
1156 Using the C<__DATA__> token creates an implicit filehandle to
1157 the file that contains the token. It is the program's
1158 responsibility to close it when it is done reading from it.
1160 This caveat is now better explained in the documentation.
1163 =head2 Diagnostics follow STDERR
1165 Diagnostic output now goes to whichever file the C<STDERR> handle
1166 is pointing at, instead of always going to the underlying C runtime
1167 library's C<stderr>.
1169 =head2 Other fixes for better diagnostics
1171 Line numbers are no longer suppressed (under most likely circumstances)
1172 during the global destruction phase.
1174 Diagnostics emitted from code running in threads other than the main
1175 thread are now accompanied by the thread ID.
1177 Embedded null characters in diagnostics now actually show up. They
1178 used to truncate the message in prior versions.
1180 $foo::a and $foo::b are now exempt from "possible typo" warnings only
1181 if sort() is encountered in package C<foo>.
1183 Unrecognized alphabetic escapes encountered when parsing quote
1184 constructs now generate a warning, since they may take on new
1185 semantics in later versions of Perl.
1187 Many diagnostics now report the internal operation in which the warning
1188 was provoked, like so:
1190 Use of uninitialized value in concatenation (.) at (eval 1) line 1.
1191 Use of uninitialized value in print at (eval 1) line 1.
1193 Diagnostics that occur within eval may also report the file and line
1194 number where the eval is located, in addition to the eval sequence
1195 number and the line number within the evaluated text itself. For
1198 Not enough arguments for scalar at (eval 4)[newlib/perl5db.pl:1411] line 2, at EOF
1200 =head1 Performance enhancements
1202 =head2 Simple sort() using { $a <=> $b } and the like are optimized
1204 Many common sort() operations using a simple inlined block are now
1205 optimized for faster performance.
1207 =head2 Optimized assignments to lexical variables
1209 Certain operations in the RHS of assignment statements have been
1210 optimized to directly set the lexical variable on the LHS,
1211 eliminating redundant copying overheads.
1213 =head2 Faster subroutine calls
1215 Minor changes in how subroutine calls are handled internally
1216 provide marginal improvements in performance.
1218 =head1 Platform specific changes
1220 =head2 Supported platforms
1226 VM/ESA is now supported.
1230 Siemens BS2000 is now supported under the POSIX Shell.
1234 The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread
1239 GNU/Hurd is now supported.
1243 Rhapsody/Darwin is now supported.
1247 EPOC is is now supported (on Psion 5).
1257 Perl now works with djgpp 2.02 (and 2.03 alpha).
1261 Environment variable names are not converted to uppercase any more.
1265 Incorrect exit codes from backticks have been fixed.
1269 This port continues to use its own builtin globbing (not File::Glob).
1273 =head2 OS390 (OpenEdition MVS)
1275 Support for this EBCDIC platform has not been renewed in this release.
1276 There are difficulties in reconciling Perl's standardization on UTF-8
1277 as its internal representation for characters with the EBCDIC character
1278 set, because the two are incompatible.
1280 It is unclear whether future versions will renew support for this
1281 platform, but the possibility exists.
1285 Numerous revisions and extensions to configuration, build, testing, and
1286 installation process to accomodate core changes and VMS-specific options.
1288 Expand %ENV-handling code to allow runtime mapping to logical names,
1289 CLI symbols, and CRTL environ array.
1291 Extension of subprocess invocation code to accept filespecs as command
1294 Add to Perl command line processing the ability to use default file types and
1295 to recognize Unix-style C<2E<gt>&1>.
1297 Expansion of File::Spec::VMS routines, and integration into ExtUtils::MM_VMS.
1299 Extension of ExtUtils::MM_VMS to handle complex extensions more flexibly.
1301 Barewords at start of Unix-syntax paths may be treated as text rather than
1302 only as logical names.
1304 Optional secure translation of several logical names used internally by Perl.
1306 Miscellaneous bugfixing and porting of new core code to VMS.
1308 Thanks are gladly extended to the many people who have contributed VMS
1309 patches, testing, and ideas.
1313 Perl can now emulate fork() internally, using multiple interpreters running
1314 in different concurrent threads. This support must be enabled at build
1315 time. See L<perlfork> for detailed information.
1317 When given a pathname that consists only of a drivename, such as C<A:>,
1318 opendir() and stat() now use the current working directory for the drive
1319 rather than the drive root.
1321 The builtin XSUB functions in the Win32:: namespace are documented. See
1324 $^X now contains the full path name of the running executable.
1326 A Win32::GetLongPathName() function is provided to complement
1327 Win32::GetFullPathName() and Win32::GetShortPathName(). See L<Win32>.
1329 POSIX::uname() is supported.
1331 system(1,...) now returns true process IDs rather than process
1332 handles. kill() accepts any real process id, rather than strictly
1333 return values from system(1,...).
1335 For better compatibility with Unix, C<kill(0, $pid)> can now be used to
1336 test whether a process exists.
1338 The C<Shell> module is supported.
1340 Better support for building Perl under command.com in Windows 95
1343 Scripts are read in binary mode by default to allow ByteLoader (and
1344 the filter mechanism in general) to work properly. For compatibility,
1345 the DATA filehandle will be set to text mode if a carriage return is
1346 detected at the end of the line containing the __END__ or __DATA__
1347 token; if not, the DATA filehandle will be left open in binary mode.
1348 Earlier versions always opened the DATA filehandle in text mode.
1350 The glob() operator is implemented via the C<File::Glob> extension,
1351 which supports glob syntax of the C shell. This increases the flexibility
1352 of the glob() operator, but there may be compatibility issues for
1353 programs that relied on the older globbing syntax. If you want to
1354 preserve compatibility with the older syntax, you might want to run
1355 perl with C<-MFile::DosGlob>. For details and compatibility information,
1364 Compatibility tests for C<sub : attrs> vs the older C<use attrs>.
1368 Tests for new environment scalar capability (e.g., C<use Env qw($BAR);>).
1372 Tests for new environment array capability (e.g., C<use Env qw(@PATH);>).
1376 IO constants (SEEK_*, _IO*).
1380 Directory-related IO methods (new, read, close, rewind, tied delete).
1382 =item lib/io_multihomed
1384 INET sockets with multi-homed hosts.
1396 Regression tests for C<my ($x,@y,%z) : attrs> and <sub : attrs>.
1400 File test operators.
1404 Verify operations that access pad objects (lexicals and temporaries).
1408 Verify C<exists &sub> operations.
1412 =head1 Modules and Pragmata
1420 While used internally by Perl as a pragma, this module also
1421 provides a way to fetch subroutine and variable attributes.
1426 WARNING: The Compiler suite remains highly experimental. The
1427 generated code may not be correct, even it manages to execute
1430 The Perl Compiler suite has been extensively reworked for this
1431 release. More of the standard Perl testsuite passes when run
1432 under the Compiler, but there is still a significant way to
1433 go to achieve production quality compiled executables.
1437 The ByteLoader is a dedicated extension to generate and run
1438 Perl bytecode. See L<ByteLoader>.
1442 References can now be used.
1444 The new version also allows a leading underscore in constant names, but
1445 disallows a double leading underscore (as in "__LINE__"). Some other names
1446 are disallowed or warned against, including BEGIN, END, etc. Some names
1447 which were forced into main:: used to fail silently in some cases; now they're
1448 fatal (outside of main::) and an optional warning (inside of main::).
1449 The ability to detect whether a constant had been set with a given name has
1456 This pragma implements the C<\N> string escape. See L<charnames>.
1460 A C<Maxdepth> setting can be specified to avoid venturing
1461 too deeply into deep data structures. See L<Data::Dumper>.
1463 The XSUB implementation of Dump() is now automatically called if the
1464 C<Useqq> setting is not in use.
1466 Dumping C<qr//> objects works correctly.
1470 C<DB> is an experimental module that exposes a clean abstraction
1471 to Perl's debugging API.
1475 DB_File can now be built with Berkeley DB versions 1, 2 or 3.
1476 See C<ext/DB_File/Changes>.
1480 Devel::DProf, a Perl source code profiler has been added. See
1481 L<Devel::DProf> and L<dprofpp>.
1485 The Dumpvalue module provides screen dumps of Perl data.
1489 Overall, Benchmark results exhibit lower average error and better timing
1492 You can now run tests for I<n> seconds instead of guessing the right
1493 number of tests to run: e.g., timethese(-5, ...) will run each
1494 code for at least 5 CPU seconds. Zero as the "number of repetitions"
1495 means "for at least 3 CPU seconds". The output format has also
1496 changed. For example:
1498 use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
1500 will now output something like this:
1502 Benchmark: running a, b, each for at least 5 CPU seconds...
1503 a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
1504 b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
1506 New features: "each for at least N CPU seconds...", "wallclock secs",
1507 and the "@ operations/CPU second (n=operations)".
1509 timethese() now returns a reference to a hash of Benchmark objects containing
1510 the test results, keyed on the names of the tests.
1512 timethis() now returns the iterations field in the Benchmark result object
1515 timethese(), timethis(), and the new cmpthese() (see below) can also take
1516 a format specifier of 'none' to suppress output.
1518 A new function countit() is just like timeit() except that it takes a
1519 TIME instead of a COUNT.
1521 A new function cmpthese() prints a chart comparing the results of each test
1522 returned from a timethese() call. For each possible pair of tests, the
1523 percentage speed difference (iters/sec or seconds/iter) is shown.
1525 For other details, see L<Benchmark>.
1529 The Devel::Peek module provides access to the internal representation
1530 of Perl variables and data. It is a data debugging tool for the XS programmer.
1534 $PERL_VERSION now stands for C<$^V> (a string value) rather than for C<$]>
1539 Env now supports accessing environment variables like PATH as array
1544 More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for
1545 large file (more than 4GB) access (NOTE: the O_LARGEFILE is
1546 automatically added to sysopen() flags if large file support has been
1547 configured, as is the default), Free/Net/OpenBSD locking behaviour
1548 flags F_FLOCK, F_POSIX, Linux F_SHLCK, and O_ACCMODE: the combined
1549 mask of O_RDONLY, O_WRONLY, and O_RDWR. The seek()/sysseek()
1550 constants SEEK_SET, SEEK_CUR, and SEEK_END are available via the
1551 C<:seek> tag. The chmod()/stat() S_IF* constants and S_IS* functions
1552 are available via the C<:mode> tag.
1556 A compare_text() function has been added, which allows custom
1557 comparison functions. See L<File::Compare>.
1561 File::Find now works correctly when the wanted() function is either
1562 autoloaded or is a symbolic reference.
1564 A bug that caused File::Find to lose track of the working directory
1565 when pruning top-level directories has been fixed.
1567 File::Find now also supports several other options to control its
1568 behavior. It can follow symbolic links if the C<follow> option is
1569 specified. Enabling the C<no_chdir> option will make File::Find skip
1570 changing the current directory when walking directories. The C<untaint>
1571 flag can be useful when running with taint checks enabled.
1577 This extension implements BSD-style file globbing. By default,
1578 it will also be used for the internal implementation of the glob()
1579 operator. See L<File::Glob>.
1583 New methods have been added to the File::Spec module: devnull() returns
1584 the name of the null device (/dev/null on Unix) and tmpdir() the name of
1585 the temp directory (normally /tmp on Unix). There are now also methods
1586 to convert between absolute and relative filenames: abs2rel() and
1587 rel2abs(). For compatibility with operating systems that specify volume
1588 names in file paths, the splitpath(), splitdir(), and catdir() methods
1591 =item File::Spec::Functions
1593 The new File::Spec::Functions modules provides a function interface
1594 to the File::Spec module. Allows shorthand
1596 $fullname = catfile($dir1, $dir2, $file);
1600 $fullname = File::Spec->catfile($dir1, $dir2, $file);
1604 Getopt::Long licensing has changed to allow the Perl Artistic License
1605 as well as the GPL. It used to be GPL only, which got in the way of
1606 non-GPL applications that wanted to use Getopt::Long.
1608 Getopt::Long encourages the use of Pod::Usage to produce help
1609 messages. For example:
1615 GetOptions('help|?' => \$help, man => \$man) or pod2usage(2);
1616 pod2usage(1) if $help;
1617 pod2usage(-exitstatus => 0, -verbose => 2) if $man;
1623 sample - Using GetOpt::Long and Pod::Usage
1627 sample [options] [file ...]
1630 -help brief help message
1631 -man full documentation
1639 Print a brief help message and exits.
1643 Prints the manual page and exits.
1649 B<This program> will read the given input file(s) and do someting
1650 useful with the contents thereof.
1654 See L<Pod::Usage> for details.
1656 A bug that prevented the non-option call-back <> from being
1657 specified as the first argument has been fixed.
1659 To specify the characters < and > as option starters, use ><. Note,
1660 however, that changing option starters is strongly deprecated.
1664 write() and syswrite() will now accept a single-argument
1665 form of the call, for consistency with Perl's syswrite().
1667 You can now create a TCP-based IO::Socket::INET without forcing
1668 a connect attempt. This allows you to configure its options
1669 (like making it non-blocking) and then call connect() manually.
1671 A bug that prevented the IO::Socket::protocol() accessor
1672 from ever returning the correct value has been corrected.
1674 IO::Socket::connect now uses non-blocking IO instead of alarm()
1675 to do connect timeouts.
1677 IO::Socket::accept now uses select() instead of alarm() for doing
1680 IO::Socket::INET->new now sets $! correctly on failure. $@ is
1681 still set for backwards compatability.
1685 Java Perl Lingo is now distributed with Perl. See jpl/README
1686 for more information.
1690 C<use lib> now weeds out any trailing duplicate entries.
1691 C<no lib> removes all named entries.
1695 The bitwise operations C<<< << >>>, C<<< >> >>>, C<&>, C<|>,
1696 and C<~> are now supported on bigints.
1700 The accessor methods Re, Im, arg, abs, rho, and theta can now also
1701 act as mutators (accessor $z->Re(), mutator $z->Re(3)).
1703 The class method C<display_format> and the corresponding object method
1704 C<display_format>, in addition to accepting just one argument, now can
1705 also accept a parameter hash. Recognized keys of a parameter hash are
1706 C<"style">, which corresponds to the old one parameter case, and two
1707 new parameters: C<"format">, which is a printf()-style format string
1708 (defaults usually to C<"%.15g">, you can revert to the default by
1709 setting the format string to C<undef>) used for both parts of a
1710 complex number, and C<"polar_pretty_print"> (defaults to true),
1711 which controls whether an attempt is made to try to recognize small
1712 multiples and rationals of pi (2pi, pi/2) at the argument (angle) of a
1713 polar complex number.
1715 The potentially disruptive change is that in list context both methods
1716 now I<return the parameter hash>, instead of only the value of the
1717 C<"style"> parameter.
1721 A little bit of radial trigonometry (cylindrical and spherical),
1722 radial coordinate conversions, and the great circle distance were added.
1724 =item Pod::Parser, Pod::InputObjects
1726 Pod::Parser is a base class for parsing and selecting sections of
1727 pod documentation from an input stream. This module takes care of
1728 identifying pod paragraphs and commands in the input and hands off the
1729 parsed paragraphs and commands to user-defined methods which are free
1730 to interpret or translate them as they see fit.
1732 Pod::InputObjects defines some input objects needed by Pod::Parser, and
1733 for advanced users of Pod::Parser that need more about a command besides
1736 As of release 5.6.0 of Perl, Pod::Parser is now the officially sanctioned
1737 "base parser code" recommended for use by all pod2xxx translators.
1738 Pod::Text (pod2text) and Pod::Man (pod2man) have already been converted
1739 to use Pod::Parser and efforts to convert Pod::HTML (pod2html) are already
1740 underway. For any questions or comments about pod parsing and translating
1741 issues and utilities, please use the pod-people@perl.org mailing list.
1743 For further information, please see L<Pod::Parser> and L<Pod::InputObjects>.
1745 =item Pod::Checker, podchecker
1747 This utility checks pod files for correct syntax, according to
1748 L<perlpod>. Obvious errors are flagged as such, while warnings are
1749 printed for mistakes that can be handled gracefully. The checklist is
1750 not complete yet. See L<Pod::Checker>.
1752 =item Pod::ParseUtils, Pod::Find
1754 These modules provide a set of gizmos that are useful mainly for pod
1755 translators. L<Pod::Find|Pod::Find> traverses directory structures and
1756 returns found pod files, along with their canonical names (like
1757 C<File::Spec::Unix>). L<Pod::ParseUtils|Pod::ParseUtils> contains
1758 B<Pod::List> (useful for storing pod list information), B<Pod::Hyperlink>
1759 (for parsing the contents of C<LE<lt>E<gt>> sequences) and B<Pod::Cache>
1760 (for caching information about pod files, e.g., link nodes).
1762 =item Pod::Select, podselect
1764 Pod::Select is a subclass of Pod::Parser which provides a function
1765 named "podselect()" to filter out user-specified sections of raw pod
1766 documentation from an input stream. podselect is a script that provides
1767 access to Pod::Select from other scripts to be used as a filter.
1770 =item Pod::Usage, pod2usage
1772 Pod::Usage provides the function "pod2usage()" to print usage messages for
1773 a Perl script based on its embedded pod documentation. The pod2usage()
1774 function is generally useful to all script authors since it lets them
1775 write and maintain a single source (the pods) for documentation, thus
1776 removing the need to create and maintain redundant usage message text
1777 consisting of information already in the pods.
1779 There is also a pod2usage script which can be used from other kinds of
1780 scripts to print usage messages from pods (even for non-Perl scripts
1781 with pods embedded in comments).
1783 For details and examples, please see L<Pod::Usage>.
1785 =item Pod::Text and Pod::Man
1787 Pod::Text has been rewritten to use Pod::Parser. While pod2text() is
1788 still available for backwards compatibility, the module now has a new
1789 preferred interface. See L<Pod::Text> for the details. The new Pod::Text
1790 module is easily subclassed for tweaks to the output, and two such
1791 subclasses (Pod::Text::Termcap for man-page-style bold and underlining
1792 using termcap information, and Pod::Text::Color for markup with ANSI color
1793 sequences) are now standard.
1795 pod2man has been turned into a module, Pod::Man, which also uses
1796 Pod::Parser. In the process, several outstanding bugs related to quotes
1797 in section headers, quoting of code escapes, and nested lists have been
1798 fixed. pod2man is now a wrapper script around this module.
1802 An EXISTS method has been added to this module (and sdbm_exists() has
1803 been added to the underlying sdbm library), so one can now call exists
1804 on an SDBM_File tied hash and get the correct result, rather than a
1807 A bug that may have caused data loss when more than one disk block
1808 happens to be read from the database in a single FETCH() has been
1813 Sys::Syslog now uses XSUBs to access facilities from syslog.h so it
1814 no longer requires syslog.ph to exist.
1818 Sys::Hostname now uses XSUBs to call the C library's gethostname() or
1819 uname() if they exist.
1821 =item Term::ANSIColor
1823 Term::ANSIColor is a very simple module to provide easy and readable
1824 access to the ANSI color and highlighting escape sequences, supported by
1825 most ANSI terminal emulators. It is now included standard.
1829 The timelocal() and timegm() functions used to silently return bogus
1830 results when the date fell outside the machine's integer range. They
1831 now consistently croak() if the date falls in an unsupported range.
1835 The error return value in list context has been changed for all functions
1836 that return a list of values. Previously these functions returned a list
1837 with a single element C<undef> if an error occurred. Now these functions
1838 return the empty list in these situations. This applies to the following
1844 The remaining functions are unchanged and continue to return C<undef> on
1845 error even in list context.
1847 The Win32::SetLastError(ERROR) function has been added as a complement
1848 to the Win32::GetLastError() function.
1850 The new Win32::GetFullPathName(FILENAME) returns the full absolute
1851 pathname for FILENAME in scalar context. In list context it returns
1852 a two-element list containing the fully qualified directory name and
1853 the filename. See L<Win32>.
1857 A new feature called "DBM Filters" has been added to all the
1858 DBM modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File.
1859 DBM Filters add four new methods to each DBM module:
1866 These can be used to filter key-value pairs before the pairs are
1867 written to the database or just after they are read from the database.
1868 See L<perldbmfilter> for further information.
1874 C<use attrs> is now obsolete, and is only provided for
1875 backward-compatibility. It's been replaced by the C<sub : attributes>
1876 syntax. See L<perlsub/"Subroutine Attributes"> and L<attributes>.
1878 Lexical warnings pragma, C<use warnings;>, to control optional warnings.
1881 C<use filetest> to control the behaviour of filetests (C<-r> C<-w>
1882 ...). Currently only one subpragma implemented, "use filetest
1883 'access';", that uses access(2) or equivalent to check permissions
1884 instead of using stat(2) as usual. This matters in filesystems
1885 where there are ACLs (access control lists): the stat(2) might lie,
1886 but access(2) knows better.
1888 =head1 Utility Changes
1892 C<perlcc> now supports the C and Bytecode backends. By default,
1893 it generates output from the simple C backend rather than the
1894 optimized C backend.
1896 Support for non-Unix platforms has been improved.
1900 C<perldoc> has been reworked to avoid possible security holes.
1901 It will not by default let itself be run as the superuser, but you
1902 may still use the B<-U> switch to try to make it drop privileges
1905 =head2 The Perl Debugger
1907 Many bug fixes and enhancements were added to F<perl5db.pl>, the
1908 Perl debugger. The help documentation was rearranged. New commands
1909 include C<< < ? >>, C<< > ? >>, and C<< { ? >> to list out current
1910 actions, C<man I<docpage>> to run your doc viewer on some perl
1911 docset, and support for quoted options. The help information was
1912 rearranged, and should be viewable once again if you're using B<less>
1913 as your pager. A serious security hole was plugged--you should
1914 immediately remove all older versions of the Perl debugger as
1915 installed in previous releases, all the way back to perl3, from
1916 your system to avoid being bitten by this.
1918 =head1 Documentation Changes
1924 The official list of public Perl API functions.
1926 =item perlcompile.pod
1928 An introduction to using the Perl Compiler suite.
1932 All material unrelated to running the Perl debugger, plus all
1933 low-level guts-like details that risked crushing the casual user
1934 of the debugger, have been relocated from the old manpage to the
1937 =item perldebguts.pod
1939 This new manpage contains excessively low-level material not related
1940 to the Perl debugger, but slightly related to debugging Perl itself.
1941 It also contains some arcane internal details of how the debugging
1942 process works that may only be of interest to developers of Perl
1945 =item perlfilter.pod
1947 An introduction to writing Perl source filters.
1951 Some guidelines for hacking the Perl source code.
1953 =item perlintern.pod
1955 A list of internal functions in the Perl source code.
1956 (List is currently empty.)
1958 =item perlopentut.pod
1960 A tutorial on using open() effectively.
1962 =item perlreftut.pod
1964 A tutorial that introduces the essentials of references.
1968 A tutorial for beginners on object-oriented Perl.
1972 A tutorial on managing class data for object modules.
1974 =item perlunicode.pod
1976 An introduction to Unicode support features in Perl.
1980 =head1 New or Changed Diagnostics
1984 =item "%s" variable %s masks earlier declaration in same %s
1986 (W misc) A "my" or "our" variable has been redeclared in the current scope or statement,
1987 effectively eliminating all access to the previous instance. This is almost
1988 always a typographical error. Note that the earlier variable will still exist
1989 until the end of the scope or until all closure referents to it are
1992 =item "my sub" not yet implemented
1994 (F) Lexically scoped subroutines are not yet implemented. Don't try that
1997 =item "our" variable %s redeclared
1999 (W misc) You seem to have already declared the same global once before in the
2000 current lexical scope.
2002 =item '!' allowed only after types %s
2004 (F) The '!' is allowed in pack() and unpack() only after certain types.
2005 See L<perlfunc/pack>.
2007 =item / cannot take a count
2009 (F) You had an unpack template indicating a counted-length string,
2010 but you have also specified an explicit size for the string.
2011 See L<perlfunc/pack>.
2013 =item / must be followed by a, A or Z
2015 (F) You had an unpack template indicating a counted-length string,
2016 which must be followed by one of the letters a, A or Z
2017 to indicate what sort of string is to be unpacked.
2018 See L<perlfunc/pack>.
2020 =item / must be followed by a*, A* or Z*
2022 (F) You had a pack template indicating a counted-length string,
2023 Currently the only things that can have their length counted are a*, A* or Z*.
2024 See L<perlfunc/pack>.
2026 =item / must follow a numeric type
2028 (F) You had an unpack template that contained a '#',
2029 but this did not follow some numeric unpack specification.
2030 See L<perlfunc/pack>.
2032 =item /%s/: Unrecognized escape \\%c passed through
2034 (W regexp) You used a backslash-character combination which is not recognized
2035 by Perl. This combination appears in an interpolated variable or a
2036 C<'>-delimited regular expression. The character was understood literally.
2038 =item /%s/: Unrecognized escape \\%c in character class passed through
2040 (W regexp) You used a backslash-character combination which is not recognized
2041 by Perl inside character classes. The character was understood literally.
2043 =item /%s/ should probably be written as "%s"
2045 (W syntax) You have used a pattern where Perl expected to find a string,
2046 as in the first argument to C<join>. Perl will treat the true
2047 or false result of matching the pattern against $_ as the string,
2048 which is probably not what you had in mind.
2050 =item %s() called too early to check prototype
2052 (W prototype) You've called a function that has a prototype before the parser saw a
2053 definition or declaration for it, and Perl could not check that the call
2054 conforms to the prototype. You need to either add an early prototype
2055 declaration for the subroutine in question, or move the subroutine
2056 definition ahead of the call to get proper prototype checking. Alternatively,
2057 if you are certain that you're calling the function correctly, you may put
2058 an ampersand before the name to avoid the warning. See L<perlsub>.
2060 =item %s argument is not a HASH or ARRAY element
2062 (F) The argument to exists() must be a hash or array element, such as:
2065 $ref->[12]->["susie"]
2067 =item %s argument is not a HASH or ARRAY element or slice
2069 (F) The argument to delete() must be either a hash or array element, such as:
2072 $ref->[12]->["susie"]
2074 or a hash or array slice, such as:
2076 @foo[$bar, $baz, $xyzzy]
2077 @{$ref->[12]}{"susie", "queue"}
2079 =item %s argument is not a subroutine name
2081 (F) The argument to exists() for C<exists &sub> must be a subroutine
2082 name, and not a subroutine call. C<exists &sub()> will generate this error.
2084 =item %s package attribute may clash with future reserved word: %s
2086 (W reserved) A lowercase attribute name was used that had a package-specific handler.
2087 That name might have a meaning to Perl itself some day, even though it
2088 doesn't yet. Perhaps you should use a mixed-case attribute name, instead.
2091 =item (in cleanup) %s
2093 (W misc) This prefix usually indicates that a DESTROY() method raised
2094 the indicated exception. Since destructors are usually called by
2095 the system at arbitrary points during execution, and often a vast
2096 number of times, the warning is issued only once for any number
2097 of failures that would otherwise result in the same message being
2100 Failure of user callbacks dispatched using the C<G_KEEPERR> flag
2101 could also result in this warning. See L<perlcall/G_KEEPERR>.
2103 =item <> should be quotes
2105 (F) You wrote C<< require <file> >> when you should have written
2108 =item Attempt to join self
2110 (F) You tried to join a thread from within itself, which is an
2111 impossible task. You may be joining the wrong thread, or you may
2112 need to move the join() to some other thread.
2114 =item Bad evalled substitution pattern
2116 (F) You've used the /e switch to evaluate the replacement for a
2117 substitution, but perl found a syntax error in the code to evaluate,
2118 most likely an unexpected right brace '}'.
2120 =item Bad realloc() ignored
2122 (S) An internal routine called realloc() on something that had never been
2123 malloc()ed in the first place. Mandatory, but can be disabled by
2124 setting environment variable C<PERL_BADFREE> to 1.
2126 =item Bareword found in conditional
2128 (W bareword) The compiler found a bareword where it expected a conditional,
2129 which often indicates that an || or && was parsed as part of the
2130 last argument of the previous construct, for example:
2134 It may also indicate a misspelled constant that has been interpreted
2137 use constant TYPO => 1;
2138 if (TYOP) { print "foo" }
2140 The C<strict> pragma is useful in avoiding such errors.
2142 =item Binary number > 0b11111111111111111111111111111111 non-portable
2144 (W portable) The binary number you specified is larger than 2**32-1
2145 (4294967295) and therefore non-portable between systems. See
2146 L<perlport> for more on portability concerns.
2148 =item Bit vector size > 32 non-portable
2150 (W portable) Using bit vector sizes larger than 32 is non-portable.
2152 =item Buffer overflow in prime_env_iter: %s
2154 (W internal) A warning peculiar to VMS. While Perl was preparing to iterate over
2155 %ENV, it encountered a logical name or symbol definition which was too long,
2156 so it was truncated to the string shown.
2158 =item Can't check filesystem of script "%s"
2160 (P) For some reason you can't check the filesystem of the script for nosuid.
2162 =item Can't declare class for non-scalar %s in "%s"
2164 (S) Currently, only scalar variables can declared with a specific class
2165 qualifier in a "my" or "our" declaration. The semantics may be extended
2166 for other types of variables in future.
2168 =item Can't declare %s in "%s"
2170 (F) Only scalar, array, and hash variables may be declared as "my" or
2171 "our" variables. They must have ordinary identifiers as names.
2173 =item Can't ignore signal CHLD, forcing to default
2175 (W signal) Perl has detected that it is being run with the SIGCHLD signal
2176 (sometimes known as SIGCLD) disabled. Since disabling this signal
2177 will interfere with proper determination of exit status of child
2178 processes, Perl has reset the signal to its default value.
2179 This situation typically indicates that the parent program under
2180 which Perl may be running (e.g., cron) is being very careless.
2182 =item Can't modify non-lvalue subroutine call
2184 (F) Subroutines meant to be used in lvalue context should be declared as
2185 such, see L<perlsub/"Lvalue subroutines">.
2187 =item Can't read CRTL environ
2189 (S) A warning peculiar to VMS. Perl tried to read an element of %ENV
2190 from the CRTL's internal environment array and discovered the array was
2191 missing. You need to figure out where your CRTL misplaced its environ
2192 or define F<PERL_ENV_TABLES> (see L<perlvms>) so that environ is not searched.
2194 =item Can't remove %s: %s, skipping file
2196 (S) You requested an inplace edit without creating a backup file. Perl
2197 was unable to remove the original file to replace it with the modified
2198 file. The file was left unmodified.
2200 =item Can't return %s from lvalue subroutine
2202 (F) Perl detected an attempt to return illegal lvalues (such
2203 as temporary or readonly values) from a subroutine used as an lvalue.
2204 This is not allowed.
2206 =item Can't weaken a nonreference
2208 (F) You attempted to weaken something that was not a reference. Only
2209 references can be weakened.
2211 =item Character class [:%s:] unknown
2213 (F) The class in the character class [: :] syntax is unknown.
2216 =item Character class syntax [%s] belongs inside character classes
2218 (W unsafe) The character class constructs [: :], [= =], and [. .] go
2219 I<inside> character classes, the [] are part of the construct,
2220 for example: /[012[:alpha:]345]/. Note that [= =] and [. .]
2221 are not currently implemented; they are simply placeholders for
2224 =item Constant is not %s reference
2226 (F) A constant value (perhaps declared using the C<use constant> pragma)
2227 is being dereferenced, but it amounts to the wrong type of reference. The
2228 message indicates the type of reference that was expected. This usually
2229 indicates a syntax error in dereferencing the constant value.
2230 See L<perlsub/"Constant Functions"> and L<constant>.
2232 =item constant(%s): %s
2234 (F) The parser found inconsistencies either while attempting to define an
2235 overloaded constant, or when trying to find the character name specified
2236 in the C<\N{...}> escape. Perhaps you forgot to load the corresponding
2237 C<overload> or C<charnames> pragma? See L<charnames> and L<overload>.
2239 =item CORE::%s is not a keyword
2241 (F) The CORE:: namespace is reserved for Perl keywords.
2243 =item defined(@array) is deprecated
2245 (D) defined() is not usually useful on arrays because it checks for an
2246 undefined I<scalar> value. If you want to see if the array is empty,
2247 just use C<if (@array) { # not empty }> for example.
2249 =item defined(%hash) is deprecated
2251 (D) defined() is not usually useful on hashes because it checks for an
2252 undefined I<scalar> value. If you want to see if the hash is empty,
2253 just use C<if (%hash) { # not empty }> for example.
2255 =item Did not produce a valid header
2259 =item (Did you mean "local" instead of "our"?)
2261 (W misc) Remember that "our" does not localize the declared global variable.
2262 You have declared it again in the same lexical scope, which seems superfluous.
2264 =item Document contains no data
2268 =item entering effective %s failed
2270 (F) While under the C<use filetest> pragma, switching the real and
2271 effective uids or gids failed.
2273 =item false [] range "%s" in regexp
2275 (W regexp) A character class range must start and end at a literal character, not
2276 another character class like C<\d> or C<[:alpha:]>. The "-" in your false
2277 range is interpreted as a literal "-". Consider quoting the "-", "\-".
2280 =item Filehandle %s opened only for output
2282 (W io) You tried to read from a filehandle opened only for writing. If you
2283 intended it to be a read/write filehandle, you needed to open it with
2284 "+<" or "+>" or "+>>" instead of with "<" or nothing. If
2285 you intended only to read from the file, use "<". See
2288 =item flock() on closed filehandle %s
2290 (W closed) The filehandle you're attempting to flock() got itself closed some
2291 time before now. Check your logic flow. flock() operates on filehandles.
2292 Are you attempting to call flock() on a dirhandle by the same name?
2294 =item Global symbol "%s" requires explicit package name
2296 (F) You've said "use strict vars", which indicates that all variables
2297 must either be lexically scoped (using "my"), declared beforehand using
2298 "our", or explicitly qualified to say which package the global variable
2301 =item Hexadecimal number > 0xffffffff non-portable
2303 (W portable) The hexadecimal number you specified is larger than 2**32-1
2304 (4294967295) and therefore non-portable between systems. See
2305 L<perlport> for more on portability concerns.
2307 =item Ill-formed CRTL environ value "%s"
2309 (W internal) A warning peculiar to VMS. Perl tried to read the CRTL's internal
2310 environ array, and encountered an element without the C<=> delimiter
2311 used to spearate keys from values. The element is ignored.
2313 =item Ill-formed message in prime_env_iter: |%s|
2315 (W internal) A warning peculiar to VMS. Perl tried to read a logical name
2316 or CLI symbol definition when preparing to iterate over %ENV, and
2317 didn't see the expected delimiter between key and value, so the
2320 =item Illegal binary digit %s
2322 (F) You used a digit other than 0 or 1 in a binary number.
2324 =item Illegal binary digit %s ignored
2326 (W digit) You may have tried to use a digit other than 0 or 1 in a binary number.
2327 Interpretation of the binary number stopped before the offending digit.
2329 =item Illegal number of bits in vec
2331 (F) The number of bits in vec() (the third argument) must be a power of
2332 two from 1 to 32 (or 64, if your platform supports that).
2334 =item Integer overflow in %s number
2336 (W overflow) The hexadecimal, octal or binary number you have specified either
2337 as a literal or as an argument to hex() or oct() is too big for your
2338 architecture, and has been converted to a floating point number. On a
2339 32-bit architecture the largest hexadecimal, octal or binary number
2340 representable without overflow is 0xFFFFFFFF, 037777777777, or
2341 0b11111111111111111111111111111111 respectively. Note that Perl
2342 transparently promotes all numbers to a floating point representation
2343 internally--subject to loss of precision errors in subsequent
2346 =item Invalid %s attribute: %s
2348 The indicated attribute for a subroutine or variable was not recognized
2349 by Perl or by a user-supplied handler. See L<attributes>.
2351 =item Invalid %s attributes: %s
2353 The indicated attributes for a subroutine or variable were not recognized
2354 by Perl or by a user-supplied handler. See L<attributes>.
2356 =item invalid [] range "%s" in regexp
2358 The offending range is now explicitly displayed.
2360 =item Invalid separator character %s in attribute list
2362 (F) Something other than a colon or whitespace was seen between the
2363 elements of an attribute list. If the previous attribute
2364 had a parenthesised parameter list, perhaps that list was terminated
2365 too soon. See L<attributes>.
2367 =item Invalid separator character %s in subroutine attribute list
2369 (F) Something other than a colon or whitespace was seen between the
2370 elements of a subroutine attribute list. If the previous attribute
2371 had a parenthesised parameter list, perhaps that list was terminated
2374 =item leaving effective %s failed
2376 (F) While under the C<use filetest> pragma, switching the real and
2377 effective uids or gids failed.
2379 =item Lvalue subs returning %s not implemented yet
2381 (F) Due to limitations in the current implementation, array and hash
2382 values cannot be returned in subroutines used in lvalue context.
2383 See L<perlsub/"Lvalue subroutines">.
2385 =item Method %s not permitted
2389 =item Missing %sbrace%s on \N{}
2391 (F) Wrong syntax of character name literal C<\N{charname}> within
2392 double-quotish context.
2394 =item Missing command in piped open
2396 (W pipe) You used the C<open(FH, "| command")> or C<open(FH, "command |")>
2397 construction, but the command was missing or blank.
2399 =item Missing name in "my sub"
2401 (F) The reserved syntax for lexically scoped subroutines requires that they
2402 have a name with which they can be found.
2404 =item No %s specified for -%c
2406 (F) The indicated command line switch needs a mandatory argument, but
2407 you haven't specified one.
2409 =item No package name allowed for variable %s in "our"
2411 (F) Fully qualified variable names are not allowed in "our" declarations,
2412 because that doesn't make much sense under existing semantics. Such
2413 syntax is reserved for future extensions.
2415 =item No space allowed after -%c
2417 (F) The argument to the indicated command line switch must follow immediately
2418 after the switch, without intervening spaces.
2420 =item no UTC offset information; assuming local time is UTC
2422 (S) A warning peculiar to VMS. Perl was unable to find the local
2423 timezone offset, so it's assuming that local system time is equivalent
2424 to UTC. If it's not, define the logical name F<SYS$TIMEZONE_DIFFERENTIAL>
2425 to translate to the number of seconds which need to be added to UTC to
2428 =item Octal number > 037777777777 non-portable
2430 (W portable) The octal number you specified is larger than 2**32-1 (4294967295)
2431 and therefore non-portable between systems. See L<perlport> for more
2432 on portability concerns.
2434 See also L<perlport> for writing portable code.
2436 =item panic: del_backref
2438 (P) Failed an internal consistency check while trying to reset a weak
2441 =item panic: kid popen errno read
2443 (F) forked child returned an incomprehensible message about its errno.
2445 =item panic: magic_killbackrefs
2447 (P) Failed an internal consistency check while trying to reset all weak
2448 references to an object.
2450 =item Parentheses missing around "%s" list
2452 (W parenthesis) You said something like
2458 my ($foo, $bar) = @_;
2460 Remember that "my", "our", and "local" bind tighter than comma.
2462 =item Possible Y2K bug: %s
2464 (W y2k) You are concatenating the number 19 with another number, which
2465 could be a potential Year 2000 problem.
2467 =item pragma "attrs" is deprecated, use "sub NAME : ATTRS" instead
2469 (W deprecated) You have written somehing like this:
2473 use attrs qw(locked);
2476 You should use the new declaration syntax instead.
2482 The C<use attrs> pragma is now obsolete, and is only provided for
2483 backward-compatibility. See L<perlsub/"Subroutine Attributes">.
2486 =item Premature end of script headers
2490 =item Repeat count in pack overflows
2492 (F) You can't specify a repeat count so large that it overflows
2493 your signed integers. See L<perlfunc/pack>.
2495 =item Repeat count in unpack overflows
2497 (F) You can't specify a repeat count so large that it overflows
2498 your signed integers. See L<perlfunc/unpack>.
2500 =item realloc() of freed memory ignored
2502 (S) An internal routine called realloc() on something that had already
2505 =item Reference is already weak
2507 (W misc) You have attempted to weaken a reference that is already weak.
2508 Doing so has no effect.
2510 =item setpgrp can't take arguments
2512 (F) Your system has the setpgrp() from BSD 4.2, which takes no arguments,
2513 unlike POSIX setpgid(), which takes a process ID and process group ID.
2515 =item Strange *+?{} on zero-length expression
2517 (W regexp) You applied a regular expression quantifier in a place where it
2518 makes no sense, such as on a zero-width assertion.
2519 Try putting the quantifier inside the assertion instead. For example,
2520 the way to match "abc" provided that it is followed by three
2521 repetitions of "xyz" is C</abc(?=(?:xyz){3})/>, not C</abc(?=xyz){3}/>.
2523 =item switching effective %s is not implemented
2525 (F) While under the C<use filetest> pragma, we cannot switch the
2526 real and effective uids or gids.
2528 =item This Perl can't reset CRTL environ elements (%s)
2530 =item This Perl can't set CRTL environ elements (%s=%s)
2532 (W internal) Warnings peculiar to VMS. You tried to change or delete an element
2533 of the CRTL's internal environ array, but your copy of Perl wasn't
2534 built with a CRTL that contained the setenv() function. You'll need to
2535 rebuild Perl with a CRTL that does, or redefine F<PERL_ENV_TABLES> (see
2536 L<perlvms>) so that the environ array isn't the target of the change to
2537 %ENV which produced the warning.
2539 =item Too late to run %s block
2541 (W void) A CHECK or INIT block is being defined during run time proper,
2542 when the opportunity to run them has already passed. Perhaps you are
2543 loading a file with C<require> or C<do> when you should be using
2544 C<use> instead. Or perhaps you should put the C<require> or C<do>
2545 inside a BEGIN block.
2547 =item Unknown open() mode '%s'
2549 (F) The second argument of 3-argument open() is not among the list
2550 of valid modes: C<< < >>, C<< > >>, C<<< >> >>>, C<< +< >>,
2551 C<< +> >>, C<<< +>> >>>, C<-|>, C<|->.
2553 =item Unknown process %x sent message to prime_env_iter: %s
2555 (P) An error peculiar to VMS. Perl was reading values for %ENV before
2556 iterating over it, and someone else stuck a message in the stream of
2557 data Perl expected. Someone's very confused, or perhaps trying to
2558 subvert Perl's population of %ENV for nefarious purposes.
2560 =item Unrecognized escape \\%c passed through
2562 (W misc) You used a backslash-character combination which is not recognized
2563 by Perl. The character was understood literally.
2565 =item Unterminated attribute parameter in attribute list
2567 (F) The lexer saw an opening (left) parenthesis character while parsing an
2568 attribute list, but the matching closing (right) parenthesis
2569 character was not found. You may need to add (or remove) a backslash
2570 character to get your parentheses to balance. See L<attributes>.
2572 =item Unterminated attribute list
2574 (F) The lexer found something other than a simple identifier at the start
2575 of an attribute, and it wasn't a semicolon or the start of a
2576 block. Perhaps you terminated the parameter list of the previous attribute
2577 too soon. See L<attributes>.
2579 =item Unterminated attribute parameter in subroutine attribute list
2581 (F) The lexer saw an opening (left) parenthesis character while parsing a
2582 subroutine attribute list, but the matching closing (right) parenthesis
2583 character was not found. You may need to add (or remove) a backslash
2584 character to get your parentheses to balance.
2586 =item Unterminated subroutine attribute list
2588 (F) The lexer found something other than a simple identifier at the start
2589 of a subroutine attribute, and it wasn't a semicolon or the start of a
2590 block. Perhaps you terminated the parameter list of the previous attribute
2593 =item Value of CLI symbol "%s" too long
2595 (W misc) A warning peculiar to VMS. Perl tried to read the value of an %ENV
2596 element from a CLI symbol table, and found a resultant string longer
2597 than 1024 characters. The return value has been truncated to 1024
2600 =item Version number must be a constant number
2602 (P) The attempt to translate a C<use Module n.n LIST> statement into
2603 its equivalent C<BEGIN> block found an internal inconsistency with
2608 =head1 Obsolete Diagnostics
2612 =item Character class syntax [: :] is reserved for future extensions
2614 (W) Within regular expression character classes ([]) the syntax beginning
2615 with "[:" and ending with ":]" is reserved for future extensions.
2616 If you need to represent those character sequences inside a regular
2617 expression character class, just quote the square brackets with the
2618 backslash: "\[:" and ":\]".
2620 =item Ill-formed logical name |%s| in prime_env_iter
2622 (W) A warning peculiar to VMS. A logical name was encountered when preparing
2623 to iterate over %ENV which violates the syntactic rules governing logical
2624 names. Because it cannot be translated normally, it is skipped, and will not
2625 appear in %ENV. This may be a benign occurrence, as some software packages
2626 might directly modify logical name tables and introduce nonstandard names,
2627 or it may indicate that a logical name table has been corrupted.
2629 =item Probable precedence problem on %s
2631 (W) The compiler found a bareword where it expected a conditional,
2632 which often indicates that an || or && was parsed as part of the
2633 last argument of the previous construct, for example:
2637 =item regexp too big
2639 (F) The current implementation of regular expressions uses shorts as
2640 address offsets within a string. Unfortunately this means that if
2641 the regular expression compiles to longer than 32767, it'll blow up.
2642 Usually when you want a regular expression this big, there is a better
2643 way to do it with multiple statements. See L<perlre>.
2645 =item Use of "$$<digit>" to mean "${$}<digit>" is deprecated
2647 (D) Perl versions before 5.004 misinterpreted any type marker followed
2648 by "$" and a digit. For example, "$$0" was incorrectly taken to mean
2649 "${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004.
2651 However, the developers of Perl 5.004 could not fix this bug completely,
2652 because at least two widely-used modules depend on the old meaning of
2653 "$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the
2654 old (broken) way inside strings; but it generates this message as a
2655 warning. And in Perl 5.005, this special treatment will cease.
2659 =head1 Known Problems
2661 =head2 Thread test failures
2663 The subtests 19 and 20 of lib/thr5005.t test are known to fail due to
2664 fundamental problems in the 5.005 threading implementation. These are
2665 not new failures--Perl 5.005_0x has the same bugs, but didn't have these
2668 =head2 EBCDIC platforms not supported
2670 In earlier releases of Perl, EBCDIC environments like OS390 (also
2671 known as Open Edition MVS) and VM-ESA were supported. Due to changes
2672 required by the UTF-8 (Unicode) support, the EBCDIC platforms are not
2673 supported in Perl 5.6.0.
2675 =head2 In 64-bit HP-UX the lib/io_multihomed test may hang
2677 The lib/io_multihomed test may hang in HP-UX if Perl has been
2678 configured to be 64-bit. Because other 64-bit platforms do not
2679 hang in this test, HP-UX is suspect. All other tests pass
2680 in 64-bit HP-UX. The test attempts to create and connect to
2681 "multihomed" sockets (sockets which have multiple IP addresses).
2683 =head2 NEXTSTEP 3.3 POSIX test failure
2685 In NEXTSTEP 3.3p2 the implementation of the strftime(3) in the
2686 operating system libraries is buggy: the %j format numbers the days of
2687 a month starting from zero, which, while being logical to programmers,
2688 will cause the subtests 19 to 27 of the lib/posix test may fail.
2690 =head2 Tru64 (aka Digital UNIX, aka DEC OSF/1) lib/sdbm test failure with gcc
2692 If compiled with gcc 2.95 the lib/sdbm test will fail (dump core).
2693 The cure is to use the vendor cc, it comes with the operating system
2694 and produces good code.
2696 =head2 UNICOS/mk CC failures during Configure run
2698 In UNICOS/mk the following errors may appear during the Configure run:
2700 Guessing which symbols your C compiler and preprocessor define...
2701 CC-20 cc: ERROR File = try.c, Line = 3
2703 bad switch yylook 79bad switch yylook 79bad switch yylook 79bad switch yylook 79#ifdef A29K
2705 4 errors detected in the compilation of "try.c".
2707 The culprit is the broken awk of UNICOS/mk. The effect is fortunately
2708 rather mild: Perl itself is not adversely affected by the error, only
2709 the h2ph utility coming with Perl, and that is rather rarely needed
2712 =head2 Arrow operator and arrays
2714 When the left argument to the arrow operator C<< -> >> is an array, or
2715 the C<scalar> operator operating on an array, the result of the
2716 operation must be considered erroneous. For example:
2721 These expressions will get run-time errors in some future release of
2724 =head2 Experimental features
2726 As discussed above, many features are still experimental. Interfaces and
2727 implementation of these features are subject to change, and in extreme cases,
2728 even subject to removal in some future release of Perl. These features
2729 include the following:
2737 =item 64-bit support
2739 =item Lvalue subroutines
2741 =item Weak references
2743 =item The pseudo-hash data type
2745 =item The Compiler suite
2747 =item Internal implementation of file globbing
2751 =item The regular expression constructs C<(?{ code })> and C<(??{ code })>
2757 If you find what you think is a bug, you might check the
2758 articles recently posted to the comp.lang.perl.misc newsgroup.
2759 There may also be information at http://www.perl.com/perl/, the Perl
2762 If you believe you have an unreported bug, please run the B<perlbug>
2763 program included with your release. Be sure to trim your bug down
2764 to a tiny but sufficient test case. Your bug report, along with the
2765 output of C<perl -V>, will be sent off to perlbug@perl.com to be
2766 analysed by the Perl porting team.
2770 The F<Changes> file for exhaustive details on what changed.
2772 The F<INSTALL> file for how to build Perl.
2774 The F<README> file for general stuff.
2776 The F<Artistic> and F<Copying> files for copyright information.
2780 Written by Gurusamy Sarathy <F<gsar@activestate.com>>, with many
2781 contributions from The Perl Porters.
2783 Send omissions or corrections to <F<perlbug@perl.com>>.