3 perldelta - what's new for perl5.005
7 This document describes differences between the 5.004 release and this one.
9 =head1 About the new versioning system
11 Perl is now developed on two tracks: a maintenance track that makes
12 small, safe updates to released production versions with emphasis on
13 compatibility; and a development track that pursues more aggressive
14 evolution. Maintenance releases (which should be considered production
15 quality) have subversion numbers that run from C<1> to C<49>, and
16 development releases (which should be considered "alpha" quality) run
19 Perl 5.005 is the combined product of the new dual-track development
22 =head1 Incompatible Changes
24 =head2 WARNING: This version is not binary compatible with Perl 5.004.
26 Starting with Perl 5.004_50 there were many deep and far-reaching changes
27 to the language internals. If you have dynamically loaded extensions
28 that you built under perl 5.003 or 5.004, you can continue to use them
29 with 5.004, but you will need to rebuild and reinstall those extensions
30 to use them 5.005. See L<INSTALL> for detailed instructions on how to
33 =head2 Default installation structure has changed
35 The new Configure defaults are designed to allow a smooth upgrade from
36 5.004 to 5.005, but you should read L<INSTALL> for a detailed
37 discussion of the changes in order to adapt them to your system.
39 =head2 Perl Source Compatibility
41 When none of the experimental features are enabled, there should be
42 very few user-visible Perl source compatibility issues.
44 If threads are enabled, then some caveats apply. C<@_> and C<$_> become
45 lexical variables. The effect of this should be largely transparent to
46 the user, but there are some boundary conditions under which user will
47 need to be aware of the issues. For example, C<local(@_)> results in
48 a "Can't localize lexical variable @_ ..." message. This may be enabled
51 Some new keywords have been introduced. These are generally expected to
52 have very little impact on compatibility. See L<New C<INIT> keyword>,
53 L<New C<lock> keyword>, and L<New C<qr//> operator>.
55 Certain barewords are now reserved. Use of these will provoke a warning
56 if you have asked for them with the C<-w> switch.
57 See L<C<our> is now a reserved word>.
59 =head2 C Source Compatibility
61 There have been a large number of changes in the internals to support
62 the new features in this release.
66 =item Core sources now require ANSI C compiler
68 An ANSI C compiler is now B<required> to build perl. See F<INSTALL>.
70 =item All Perl global variables must now be referenced with an explicit prefix
72 All Perl global variables that are visible for use by extensions now
73 have a C<PL_> prefix. New extensions should C<not> refer to perl globals
74 by their unqualified names. To preserve sanity, we provide limited
75 backward compatibility for globals that are being widely used like
76 C<sv_undef> and C<na> (which should now be written as C<PL_sv_undef>,
79 If you find that your XS extension does not compile anymore because a
80 perl global is not visible, try adding a C<PL_> prefix to the global
83 It is strongly recommended that all functions in the Perl API that don't
84 begin with C<perl> be referenced with a C<Perl_> prefix. The bare function
85 names without the C<Perl_> prefix are supported with macros, but this
86 support may cease in a future release.
88 See L<perlguts/"API LISTING">.
90 =item Enabling threads has source compatibility issues
92 Perl built with threading enabled requires extensions to use the new
93 C<dTHR> macro to initialize the handle to access per-thread data.
94 If you see a compiler error that talks about the variable C<thr> not
95 being declared (when building a module that has XS code), you need
96 to add C<dTHR;> at the beginning of the block that elicited the error.
98 The API function C<perl_get_sv("@",FALSE)> should be used instead of
99 directly accessing perl globals as C<GvSV(errgv)>. The API call is
100 backward compatible with existing perls and provides source compatibility
101 with threading is enabled.
103 See L<"C Source Compatibility"> for more information.
107 =head2 Binary Compatibility
109 This version is NOT binary compatible with older versions. All extensions
110 will need to be recompiled. Further binaries built with threads enabled
111 are incompatible with binaries built without. This should largely be
112 transparent to the user, as all binary incompatible configurations have
113 their own unique architecture name, and extension binaries get installed at
114 unique locations. This allows coexistence of several configurations in
115 the same directory hierarchy. See F<INSTALL>.
117 =head2 Security fixes may affect compatibility
119 A few taint leaks and taint omissions have been corrected. This may lead
120 to "failure" of scripts that used to work with older versions. Compiling
121 with -DINCOMPLETE_TAINTS provides a perl with minimal amounts of changes
122 to the tainting behavior. But note that the resulting perl will have
125 Oneliners with the C<-e> switch do not create temporary files anymore.
127 =head2 Relaxed new mandatory warnings introduced in 5.004
129 Many new warnings that were introduced in 5.004 have been made
130 optional. Some of these warnings are still present, but perl's new
131 features make them less often a problem. See L<New Diagnostics>.
135 Perl has a new Social Contract for contributors. See F<Porting/Contract>.
137 The license included in much of the Perl documentation has changed.
138 Most of the Perl documentation was previously under the implicit GNU
139 General Public License or the Artistic License (at the user's choice).
140 Now much of the documentation unambigously states the terms under which
141 it may be distributed. Those terms are in general much less restrictive
142 than the GNU GPL. See L<perl> and the individual perl man pages listed
150 WARNING: Threading is considered an B<experimental> feature. Details of the
151 implementation may change without notice. There are known limitations
152 and some bugs. These are expected to be fixed in future versions.
154 See L<README.threads>.
156 Mach cthreads (NEXTSTEP, OPENSTEP, Rhapsody) are now supported by
157 the Thread extension.
161 WARNING: The Compiler and related tools are considered B<experimental>.
162 Features may change without notice, and there are known limitations
163 and bugs. Since the compiler is fully external to perl, the default
164 configuration will build and install it.
166 The Compiler produces three different types of transformations of a
167 perl program. The C backend generates C code that captures perl's state
168 just before execution begins. It eliminates the compile-time overheads
169 of the regular perl interpreter, but the run-time performance remains
170 comparatively the same. The CC backend generates optimized C code
171 equivalent to the code path at run-time. The CC backend has greater
172 potential for big optimizations, but only a few optimizations are
173 implemented currently. The Bytecode backend generates a platform
174 independent bytecode representation of the interpreter's state
175 just before execution. Thus, the Bytecode back end also eliminates
176 much of the compilation overhead of the interpreter.
178 The compiler comes with several valuable utilities.
180 C<B::Lint> is an experimental module to detect and warn about suspicious
181 code, especially the cases that the C<-w> switch does not detect.
183 C<B::Deparse> can be used to demystify perl code, and understand
184 how perl optimizes certain constructs.
186 C<B::Xref> generates cross reference reports of all definition and use
187 of variables, subroutines and formats in a program.
189 C<B::Showlex> show the lexical variables used by a subroutine or file
192 C<perlcc> is a simple frontend for compiling perl.
194 See C<ext/B/README>, L<B>, and the respective compiler modules.
196 =head2 Regular Expressions
198 Perl's regular expression engine has been seriously overhauled, and
199 many new constructs are supported. Several bugs have been fixed.
201 Here is an itemized summary:
205 =item Many new and improved optimizations
207 Changes in the RE engine:
209 Unneeded nodes removed;
210 Substrings merged together;
211 New types of nodes to process (SUBEXPR)* and similar expressions
212 quickly, used if the SUBEXPR has no side effects and matches
213 strings of the same length;
214 Better optimizations by lookup for constant substrings;
215 Better search for constants substrings anchored by $ ;
217 Changes in Perl code using RE engine:
219 More optimizations to s/longer/short/;
220 study() was not working;
221 /blah/ may be optimized to an analogue of index() if $& $` $' not seen;
222 Unneeded copying of matched-against string removed;
223 Only matched part of the string is copying if $` $' were not seen;
227 Note that only the major bug fixes are listed here. See F<Changes> for others.
229 Backtracking might not restore start of $3.
230 No feedback if max count for * or + on "complex" subexpression
231 was reached, similarly (but at compile time) for {3,34567}
232 Primitive restrictions on max count introduced to decrease a
233 possibility of a segfault;
234 (ZERO-LENGTH)* could segfault;
235 (ZERO-LENGTH)* was prohibited;
236 Long REs were not allowed;
237 /RE/g could skip matches at the same position after a
240 =item New regular expression constructs
242 The following new syntax elements are supported:
249 (?(COND)YES_RE|NO_RE)
253 =item New operator for precompiled regular expressions
255 See L<New C<qr//> operator>.
257 =item Other improvements
259 Better debugging output (possibly with colors),
260 even from non-debugging Perl;
261 RE engine code now looks like C, not like assembler;
262 Behaviour of RE modifiable by `use re' directive;
263 Improved documentation;
264 Test suite significantly extended;
265 Syntax [:^upper:] etc., reserved inside character classes;
267 =item Incompatible changes
269 (?i) localized inside enclosing group;
270 $( is not interpolated into RE any more;
271 /RE/g may match at the same position (with non-zero length)
272 after a zero-length match (bug fix).
276 See L<perlre> and L<perlop>.
278 =head2 Improved malloc()
280 See banner at the beginning of C<malloc.c> for details.
282 =head2 Quicksort is internally implemented
284 Perl now contains its own highly optimized qsort() routine. The new qsort()
285 is resistant to inconsistent comparison functions, so Perl's C<sort()> will
286 not provoke coredumps any more when given poorly written sort subroutines.
287 (Some C library C<qsort()>s that were being used before used to have this
288 problem.) In our testing, the new C<qsort()> required the minimal number
289 of pair-wise compares on average, among all known C<qsort()> implementations.
291 See C<perlfunc/sort>.
293 =head2 Reliable signals
295 Perl's signal handling is susceptible to random crashes, because signals
296 arrive asynchronously, and the Perl runtime is not reentrant at arbitrary
299 However, one experimental implementation of reliable signals is available
300 when threads are enabled. See C<Thread::Signal>. Also see F<INSTALL> for
301 how to build a Perl capable of threads.
303 =head2 Reliable stack pointers
305 The internals now reallocate the perl stack only at predictable times.
306 In particular, magic calls never trigger reallocations of the stack,
307 because all reentrancy of the runtime is handled using a "stack of stacks".
308 This should improve reliability of cached stack pointers in the internals
311 =head2 More generous treatment of carriage returns
313 Perl used to complain if it encountered literal carriage returns in
314 scripts. Now they are mostly treated like whitespace within program text.
315 Inside string literals and here documents, literal carriage returns are
316 ignored if they occur paired with linefeeds, or get interpreted as whitespace
317 if they stand alone. This behavior means that literal carriage returns
318 in files should be avoided. You can get the older, more compatible (but
319 less generous) behavior by defining the preprocessor symbol
320 C<PERL_STRICT_CR> when building perl. Of course, all this has nothing
321 whatever to do with how escapes like C<\r> are handled within strings.
323 Note that this doesn't somehow magically allow you to keep all text files
324 in DOS format. The generous treatment only applies to files that perl
325 itself parses. If your C compiler doesn't allow carriage returns in
326 files, you may still be unable to build modules that need a C compiler.
330 C<substr>, C<pos> and C<vec> don't leak memory anymore when used in lvalue
331 context. Many small leaks that impacted applications that embed multiple
332 interpreters have been fixed.
334 =head2 Better support for multiple interpreters
336 The build-time option C<-DMULTIPLICITY> has had many of the details
337 reworked. Some previously global variables that should have been
338 per-interpreter now are. With care, this allows interpreters to call
339 each other. See the C<PerlInterp> extension on CPAN.
341 =head2 Behavior of local() on array and hash elements is now well-defined
343 See L<perlsub/"Temporary Values via local()">.
345 =head2 C<%!> is transparently tied to the L<Errno> module
347 See L<perlvar>, and L<Errno>.
349 =head2 Pseudo-hashes are supported
353 =head2 C<EXPR foreach EXPR> is supported
357 =head2 Keywords can be globally overridden
361 =head2 C<$^E> is meaningful on Win32
365 =head2 C<foreach (1..1000000)> optimized
367 C<foreach (1..1000000)> is now optimized into a counting loop. It does
368 not try to allocate a 1000000-size list anymore.
370 =head2 C<Foo::> can be used as implicitly quoted package name
372 Barewords caused unintuitive behavior when a subroutine with the same
373 name as a package happened to be defined. Thus, C<new Foo @args>,
374 use the result of the call to C<Foo()> instead of C<Foo> being treated
375 as a literal. The recommended way to write barewords in the indirect
376 object slot is C<new Foo:: @args>. Note that the method C<new()> is
377 called with a first argument of C<Foo>, not C<Foo::> when you do that.
379 =head2 C<exists $Foo::{Bar::}> tests existence of a package
381 It was impossible to test for the existence of a package without
382 actually creating it before. Now C<exists $Foo::{Bar::}> can be
383 used to test if the C<Foo::Bar> namespace has been created.
385 =head2 Better locale support
389 =head2 Experimental support for 64-bit platforms
391 Perl5 has always had 64-bit support on systems with 64-bit longs.
392 Starting with 5.005, the beginnings of experimental support for systems
393 with 32-bit long and 64-bit 'long long' integers has been added.
394 If you add -DUSE_LONG_LONG to your ccflags in config.sh (or manually
395 define it in perl.h) then perl will be built with 'long long' support.
396 There will be many compiler warnings, and the resultant perl may not
397 work on all systems. There are many other issues related to
398 third-party extensions and libraries. This option exists to allow
399 people to work on those issues.
401 =head2 prototype() returns useful results on builtins
403 See L<perlfunc/prototype>.
405 =head2 Extended support for exception handling
407 C<die()> now accepts a reference value, and C<$@> gets set to that
408 value in exception traps. This makes it possible to propagate
409 exception objects. This is an undocumented B<experimental> feature.
411 =head2 Re-blessing in DESTROY() supported for chaining DESTROY() methods
413 See L<perlobj/Destructors>.
415 =head2 All C<printf> format conversions are handled internally
417 See L<perlfunc/printf>.
419 =head2 New C<INIT> keyword
421 C<INIT> subs are like C<BEGIN> and C<END>, but they get run just before
422 the perl runtime begins execution. e.g., the Perl Compiler makes use of
423 C<INIT> blocks to initialize and resolve pointers to XSUBs.
425 =head2 New C<lock> keyword
427 The C<lock> keyword is the fundamental synchronization primitive
428 in threaded perl. When threads are not enabled, it is currently a noop.
430 To minimize impact on source compatibility this keyword is "weak", i.e., any
431 user-defined subroutine of the same name overrides it, unless a C<use Thread>
434 =head2 New C<qr//> operator
436 The C<qr//> operator, which is syntactically similar to the other quote-like
437 operators, is used to create precompiled regular expressions. This compiled
438 form can now be explicitly passed around in variables, and interpolated in
439 other regular expressions. See L<perlop>.
441 =head2 C<our> is now a reserved word
443 Calling a subroutine with the name C<our> will now provoke a warning when
444 using the C<-w> switch.
446 =head2 Tied arrays are now fully supported
450 =head2 Tied handles support is better
452 Several missing hooks have been added. There is also a new base class for
453 TIEARRAY implementations. See L<Tie::Array>.
455 =head2 4th argument to substr
457 substr() can now both return and replace in one operation. The optional
458 4th argument is the replacement string. See L<perlfunc/substr>.
460 =head2 Negative LENGTH argument to splice
462 splice() with a negative LENGTH argument now work similar to what the
463 LENGTH did for substr(). Previously a negative LENGTH was treated as
464 0. See L<perlfunc/splice>.
466 =head2 Magic lvalues are now more magical
468 When you say something like C<substr($x, 5) = "hi">, the scalar returned
469 by substr() is special, in that any modifications to it affect $x.
470 (This is called a 'magic lvalue' because an 'lvalue' is something on
471 the left side of an assignment.) Normally, this is exactly what you
472 would expect to happen, but Perl uses the same magic if you use substr(),
473 pos(), or vec() in a context where they might be modified, like taking
474 a reference with C<\> or as an argument to a sub that modifies C<@_>.
475 In previous versions, this 'magic' only went one way, but now changes
476 to the scalar the magic refers to ($x in the above example) affect the
477 magic lvalue too. For instance, this code now acts differently:
484 printit(substr($x, 0, 5));
486 In previous versions, this would print "hello", but it now prints "g'bye".
488 =head2 E<lt>E<gt> now reads in records
490 If C<$/> is a referenence to an integer, or a scalar that holds an integer,
491 E<lt>E<gt> will read in records instead of lines. For more info, see
494 =head2 pack() format 'Z' supported
496 The new format type 'Z' is useful for packing and unpacking null-terminated
497 strings. See L<perlfunc/"pack">.
499 =head1 Significant bug fixes
501 =head2 E<lt>HANDLEE<gt> on empty files
503 With C<$/> set to C<undef>, slurping an empty file returns a string of
504 zero length (instead of C<undef>, as it used to) for the first time the
505 HANDLE is read. Subsequent reads yield C<undef>.
507 This means that the following will append "foo" to an empty file (it used
508 to not do anything before):
510 perl -0777 -pi -e 's/^/foo/' empty_file
512 Note that the behavior of:
514 perl -pi -e 's/^/foo/' empty_file
516 is unchanged (it continues to leave the file empty).
518 =head1 Supported Platforms
520 Configure has many incremental improvements. Site-wide policy for building
521 perl can now be made persistent, via Policy.sh. Configure also records
522 the command-line arguments used in F<config.sh>.
526 BeOS is now supported. See L<README.beos>.
528 DOS is now supported under the DJGPP tools. See L<README.dos>.
530 GNU/Hurd is now supported.
532 MiNT is now supported. See L<README.mint>.
534 MPE/iX is now supported. See L<README.mpeix>.
536 MVS (aka OS390, aka Open Edition) is now supported. See L<README.os390>.
538 Stratus VOS is now supported. See L<README.vos>.
540 =head2 Changes in existing support
542 Win32 support has been vastly enhanced. Support for Perl Object, a C++
543 encapsulation of Perl. GCC and EGCS are now supported on Win32.
544 See F<README.win32>, aka L<perlwin32>.
546 VMS configuration system has been rewritten. See L<README.vms>.
548 The hints files for most Unix platforms have seen incremental improvements.
550 =head1 Modules and Pragmata
558 Perl compiler and tools. See L<B>.
562 A module to pretty print Perl data. See L<Data::Dumper>.
566 A module to dump perl values to the screen. See L<Dumpvalue>.
570 A module to look up errors more conveniently. See L<Errno>.
574 A portable API for file operations.
576 =item ExtUtils::Installed
578 Query and manage installed modules.
580 =item ExtUtils::Packlist
582 Manipulate .packlist files.
586 Make functions/builtins succeed or die.
590 Constants and other support infrastructure for System V IPC operations
595 A framework for writing testsuites.
599 Base class for tied arrays.
603 Base class for tied handles.
607 Perl thread creation, manipulation, and support.
611 Set subroutine attributes.
615 Compile-time class fields.
619 Various pragmata to control behavior of regular expressions.
623 =head2 Changes in existing modules
629 You can now run tests for I<n> seconds instead of guessing the right
630 number of tests to run: e.g. timethese(-5, ...) will run each of the
631 codes for at least 5 CPU seconds. Zero as the "number of repetitions"
632 means "for at least 3 CPU seconds". The output format has also
633 changed. For example:
635 use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
637 will now output something like this:
639 Benchmark: running a, b, each for at least 5 CPU seconds...
640 a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
641 b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
643 New features: "each for at least N CPU seconds...", "wallclock secs",
644 and the "@ operations/CPU second (n=operations)".
648 Carp has a new function cluck(). cluck() warns, like carp(), but also adds
649 a stack backtrace to the error message, like confess().
653 CGI has been updated to version 2.42.
657 More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for
658 large (more than 4G) file access (the 64-bit support is not yet
659 working, though, so no need to get overly excited), Free/Net/OpenBSD
660 locking behaviour flags F_FLOCK, F_POSIX, Linux F_SHLCK, and
661 O_ACCMODE: the mask of O_RDONLY, O_WRONLY, and O_RDWR.
665 The accessor methods Re, Im, arg, abs, rho, and theta, can now also
666 act as mutators (accessor $z->Re(), mutator $z->Re(3)).
670 A little bit of radial trigonometry (cylindrical and spherical) added:
671 radial coordinate conversions and the great circle distance.
675 POSIX now has its own platform-specific hints files.
679 DB_File supports version 2.x of Berkeley DB. See C<ext/DB_File/Changes>.
683 MakeMaker now supports writing empty makefiles, provides a way to
684 specify that site umask() policy should be honored. There is also
685 better support for manipulation of .packlist files, and getting
686 information about installed modules.
688 Extensions that have both architecture-dependent and
689 architecture-independent files are now always installed completely in
690 the architecture-dependent locations. Previously, the shareable parts
691 were shared both across architectures and across perl versions and were
692 therefore liable to be overwritten with newer versions that might have
693 subtle incompatibilities.
697 See <perlmodinstall> and L<CPAN>.
701 Cwd::cwd is faster on most platforms.
709 =head1 Utility Changes
711 C<h2ph> and related utilities have been vastly overhauled.
713 C<perlcc>, a new experimental front end for the compiler is available.
715 The crude GNU C<configure> emulator is now called C<configure.gnu> to
716 avoid trampling on C<Configure> under case-insensitive filesystems.
718 C<perldoc> used to be rather slow. The slower features are now optional.
719 In particular, case-insensitive searches need the C<-i> switch, and
720 recursive searches need C<-r>. You can set these switches in the
721 C<PERLDOC> environment variable to get the old behavior.
723 =head1 Documentation Changes
725 Config.pm now has a glossary of variables.
727 F<Porting/patching.pod> has detailed instructions on how to create and
728 submit patches for perl.
730 L<perlport> specifies guidelines on how to write portably.
732 L<perlmodinstall> describes how to fetch and install modules from C<CPAN>
735 Some more Perl traps are documented now. See L<perltrap>.
737 L<perlopentut> gives a tutorial on using open().
739 L<perlreftut> gives a tutorial on references.
741 L<perlthrtut> gives a tutorial on threads.
743 =head1 New Diagnostics
747 =item Ambiguous call resolved as CORE::%s(), qualify as such or use &
749 (W) A subroutine you have declared has the same name as a Perl keyword,
750 and you have used the name without qualification for calling one or the
751 other. Perl decided to call the builtin because the subroutine is
754 To force interpretation as a subroutine call, either put an ampersand
755 before the subroutine name, or qualify the name with its package.
756 Alternatively, you can import the subroutine (or pretend that it's
757 imported with the C<use subs> pragma).
759 To silently interpret it as the Perl operator, use the C<CORE::> prefix
760 on the operator (e.g. C<CORE::log($x)>) or by declaring the subroutine
761 to be an object method (see L<attrs>).
763 =item Bad index while coercing array into hash
765 (F) The index looked up in the hash found as the 0'th element of a
766 pseudo-hash is not legal. Index values must be at 1 or greater.
769 =item Bareword "%s" refers to nonexistent package
771 (W) You used a qualified bareword of the form C<Foo::>, but
772 the compiler saw no other uses of that namespace before that point.
773 Perhaps you need to predeclare a package?
775 =item Can't call method "%s" on an undefined value
777 (F) You used the syntax of a method call, but the slot filled by the
778 object reference or package name contains an undefined value.
779 Something like this will reproduce the error:
782 process $BADREF 1,2,3;
783 $BADREF->process(1,2,3);
785 =item Can't check filesystem of script "%s" for nosuid
787 (P) For some reason you can't check the filesystem of the script for nosuid.
789 =item Can't coerce array into hash
791 (F) You used an array where a hash was expected, but the array has no
792 information on how to map from keys to array indices. You can do that
793 only with arrays that have a hash reference at index 0.
795 =item Can't goto subroutine from an eval-string
797 (F) The "goto subroutine" call can't be used to jump out of an eval "string".
798 (You can use it to jump out of an eval {BLOCK}, but you probably don't want to.)
800 =item Can't localize pseudo-hash element
802 (F) You said something like C<local $ar-E<gt>{'key'}>, where $ar is
803 a reference to a pseudo-hash. That hasn't been implemented yet, but
804 you can get a similar effect by localizing the corresponding array
805 element directly -- C<local $ar-E<gt>[$ar-E<gt>[0]{'key'}]>.
807 =item Can't use %%! because Errno.pm is not available
809 (F) The first time the %! hash is used, perl automatically loads the
810 Errno.pm module. The Errno module is expected to tie the %! hash to
811 provide symbolic names for C<$!> errno values.
813 =item Cannot find an opnumber for "%s"
815 (F) A string of a form C<CORE::word> was given to prototype(), but
816 there is no builtin with the name C<word>.
818 =item Character class syntax [. .] is reserved for future extensions
820 (W) Within regular expression character classes ([]) the syntax beginning
821 with "[." and ending with ".]" is reserved for future extensions.
822 If you need to represent those character sequences inside a regular
823 expression character class, just quote the square brackets with the
824 backslash: "\[." and ".\]".
826 =item Character class syntax [: :] is reserved for future extensions
828 (W) Within regular expression character classes ([]) the syntax beginning
829 with "[:" and ending with ":]" is reserved for future extensions.
830 If you need to represent those character sequences inside a regular
831 expression character class, just quote the square brackets with the
832 backslash: "\[:" and ":\]".
834 =item Character class syntax [= =] is reserved for future extensions
836 (W) Within regular expression character classes ([]) the syntax
837 beginning with "[=" and ending with "=]" is reserved for future extensions.
838 If you need to represent those character sequences inside a regular
839 expression character class, just quote the square brackets with the
840 backslash: "\[=" and "=\]".
842 =item %s: Eval-group in insecure regular expression
844 (F) Perl detected tainted data when trying to compile a regular expression
845 that contains the C<(?{ ... })> zero-width assertion, which is unsafe.
846 See L<perlre/(?{ code })>, and L<perlsec>.
848 =item %s: Eval-group not allowed, use re 'eval'
850 (F) A regular expression contained the C<(?{ ... })> zero-width assertion,
851 but that construct is only allowed when the C<use re 'eval'> pragma is
852 in effect. See L<perlre/(?{ code })>.
854 =item %s: Eval-group not allowed at run time
856 (F) Perl tried to compile a regular expression containing the C<(?{ ... })>
857 zero-width assertion at run time, as it would when the pattern contains
858 interpolated values. Since that is a security risk, it is not allowed.
859 If you insist, you may still do this by explicitly building the pattern
860 from an interpolated string at run time and using that in an eval().
861 See L<perlre/(?{ code })>.
863 =item Explicit blessing to '' (assuming package main)
865 (W) You are blessing a reference to a zero length string. This has
866 the effect of blessing the reference into the package main. This is
867 usually not what you want. Consider providing a default target
868 package, e.g. bless($ref, $p || 'MyPackage');
870 =item Illegal hex digit ignored
872 (W) You may have tried to use a character other than 0 - 9 or A - F in a
873 hexadecimal number. Interpretation of the hexadecimal number stopped
874 before the illegal character.
876 =item No such array field
878 (F) You tried to access an array as a hash, but the field name used is
879 not defined. The hash at index 0 should map all valid field names to
880 array indices for that to work.
882 =item No such field "%s" in variable %s of type %s
884 (F) You tried to access a field of a typed variable where the type
885 does not know about the field name. The field names are looked up in
886 the %FIELDS hash in the type package at compile time. The %FIELDS hash
887 is usually set up with the 'fields' pragma.
889 =item Out of memory during ridiculously large request
891 (F) You can't allocate more than 2^31+"small amount" bytes. This error
892 is most likely to be caused by a typo in the Perl program. e.g., C<$arr[time]>
893 instead of C<$arr[$time]>.
895 =item Range iterator outside integer range
897 (F) One (or both) of the numeric arguments to the range operator ".."
898 are outside the range which can be represented by integers internally.
899 One possible workaround is to force Perl to use magical string
900 increment by prepending "0" to your numbers.
902 =item Recursive inheritance detected while looking for method '%s' in package '%s'
904 (F) More than 100 levels of inheritance were encountered while invoking a
905 method. Probably indicates an unintended loop in your inheritance hierarchy.
907 =item Reference found where even-sized list expected
909 (W) You gave a single reference where Perl was expecting a list with
910 an even number of elements (for assignment to a hash). This
911 usually means that you used the anon hash constructor when you meant
912 to use parens. In any case, a hash requires key/value B<pairs>.
914 %hash = { one => 1, two => 2, }; # WRONG
915 %hash = [ qw/ an anon array / ]; # WRONG
916 %hash = ( one => 1, two => 2, ); # right
917 %hash = qw( one 1 two 2 ); # also fine
919 =item Undefined value assigned to typeglob
921 (W) An undefined value was assigned to a typeglob, a la C<*foo = undef>.
922 This does nothing. It's possible that you really mean C<undef *foo>.
924 =item Use of reserved word "%s" is deprecated
926 (D) The indicated bareword is a reserved word. Future versions of perl
927 may use it as a keyword, so you're better off either explicitly quoting
928 the word in a manner appropriate for its context of use, or using a
929 different name altogether. The warning can be suppressed for subroutine
930 names by either adding a C<&> prefix, or using a package qualifier,
931 e.g. C<&our()>, or C<Foo::our()>.
933 =item perl: warning: Setting locale failed.
935 (S) The whole warning message will look something like:
937 perl: warning: Setting locale failed.
938 perl: warning: Please check that your locale settings:
941 are supported and installed on your system.
942 perl: warning: Falling back to the standard locale ("C").
944 Exactly what were the failed locale settings varies. In the above the
945 settings were that the LC_ALL was "En_US" and the LANG had no value.
946 This error means that Perl detected that you and/or your system
947 administrator have set up the so-called variable system but Perl could
948 not use those settings. This was not dead serious, fortunately: there
949 is a "default locale" called "C" that Perl can and will use, the
950 script will be run. Before you really fix the problem, however, you
951 will get the same error message each time you run Perl. How to really
952 fix the problem can be found in L<perllocale/"LOCALE PROBLEMS">.
957 =head1 Obsolete Diagnostics
963 (F) The mktemp() routine failed for some reason while trying to process
964 a B<-e> switch. Maybe your /tmp partition is full, or clobbered.
966 Removed because B<-e> doesn't use temporary files any more.
968 =item Can't write to temp file for B<-e>: %s
970 (F) The write routine failed for some reason while trying to process
971 a B<-e> switch. Maybe your /tmp partition is full, or clobbered.
973 Removed because B<-e> doesn't use temporary files any more.
975 =item Cannot open temporary file
977 (F) The create routine failed for some reason while trying to process
978 a B<-e> switch. Maybe your /tmp partition is full, or clobbered.
980 Removed because B<-e> doesn't use temporary files any more.
984 (F) The current implementation of regular expressions uses shorts as
985 address offsets within a string. Unfortunately this means that if
986 the regular expression compiles to longer than 32767, it'll blow up.
987 Usually when you want a regular expression this big, there is a better
988 way to do it with multiple statements. See L<perlre>.
992 =head1 Configuration Changes
994 You can use "Configure -Uinstallusrbinperl" which causes installperl
995 to skip installing perl also as /usr/bin/perl. This is useful if you
996 prefer not to modify /usr/bin for some reason or another but harmful
997 because many scripts assume to find Perl in /usr/bin/perl.
1001 If you find what you think is a bug, you might check the headers of
1002 recently posted articles in the comp.lang.perl.misc newsgroup.
1003 There may also be information at http://www.perl.com/perl/, the Perl
1006 If you believe you have an unreported bug, please run the B<perlbug>
1007 program included with your release. Make sure you trim your bug down
1008 to a tiny but sufficient test case. Your bug report, along with the
1009 output of C<perl -V>, will be sent off to <F<perlbug@perl.com>> to be
1010 analysed by the Perl porting team.
1014 The F<Changes> file for exhaustive details on what changed.
1016 The F<INSTALL> file for how to build Perl.
1018 The F<README> file for general stuff.
1020 The F<Artistic> and F<Copying> files for copyright information.
1024 Written by Gurusamy Sarathy <F<gsar@umich.edu>>, with many contributions
1025 from The Perl Porters.
1027 Send omissions or corrections to <F<perlbug@perl.com>>.