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1=head1 NAME
2
a5222a85 3perldelta - what's new for perl v5.6 (as of v5.005_62)
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4
5=head1 DESCRIPTION
6
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7This is an unsupported alpha release, meant for intrepid Perl developers
8only. The included sources may not even build correctly on some platforms.
9Subscribing to perl5-porters is the best way to monitor and contribute
10to the progress of development releases (see www.perl.org for info).
11
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12This document describes differences between the 5.005 release and this one.
13
14=head1 Incompatible Changes
15
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16=head2 Perl Source Incompatibilities
17
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18Beware that any new warnings that have been added or enhanced old
19warnings are B<not> considered incompatible changes.
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20
21Since all new warnings must be explicitly requested via the C<-w>
22switch or the C<warnings> pragma, it is ultimately the programmer's
23responsibility to ensure that warnings are enabled judiciously.
e02fdbd2 24
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25=over 4
26
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27=item Treatment of list slices of undef has changed
28
29When taking a slice of a literal list (as opposed to a slice of
30an array or hash), Perl used to return an empty list if the
31result happened to be composed of all undef values.
32
33The new behavior is to produce an empty list if (and only if)
34the original list was empty. Consider the following example:
35
36 @a = (1,undef,undef,2)[2,1,2];
37
38The old behavior would have resulted in @a having no elements.
39The new behavior ensures it has three undefined elements.
40
41Note in particular that the behavior of slices of the following
42cases remains unchanged:
43
44 @a = ()[1,2];
45 @a = (getpwent)[7,0];
46 @a = (anything_returning_empty_list())[2,1,2];
47 @a = @b[2,1,2];
48 @a = @c{'a','b','c'};
49
50See L<perldata>.
51
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52=item Possibly changed pseudo-random number generator
53
54In 5.005_0x and earlier, perl's rand() function used the C library
55rand(3) function. As of 5.005_52, Configure tests for drand48(),
56random(), and rand() (in that order) and picks the first one it finds.
57Perl programs that depend on reproducing a specific set of pseudo-random
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58numbers will now likely produce different output. You can use
59C<sh Configure -Drandfunc=rand> to obtain the old behavior.
757edf6f 60
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61=item Hashing function for hash keys has changed
62
63Perl hashes are not order preserving. The apparently random order
64encountered when iterating on the contents of a hash is determined
65by the hashing algorithm used. To improve the distribution of lower
66bits in the hashed value, the algorithm has changed slightly as of
675.005_52. When iterating over hashes, this may yield a random order
68that is B<different> from that of previous versions.
69
70=item C<undef> fails on read only values
71
72Using the C<undef> operator on a readonly value (such as $1) has
73the same effect as assigning C<undef> to the readonly value--it
74throws an exception.
75
76=item Close-on-exec bit may be set on pipe() handles
77
78On systems that support a close-on-exec flag on filehandles, the
79flag will be set for any handles created by pipe(), if that is
80warranted by the value of $^F that may be in effect. Earlier
81versions neglected to set the flag for handles created with
82pipe(). See L<perlfunc/pipe> and L<perlvar/$^F>.
83
84=item Writing C<"$$1"> to mean C<"${$}1"> is unsupported
85
86Perl 5.004 deprecated the interpretation of C<$$1> and
87similar within interpolated strings to mean C<$$ . "1">,
88but still allowed it.
89
90In Perl 5.6 and later, C<"$$1"> always means C<"${$1}">.
91
92=item values(%h) and C<\(%h)> operate on aliases to values, not copies
93
94each(), values() and hashes in a list context return the actual
95values in the hash, instead of copies (as they used to in earlier
96versions). Typical idioms for using these constructs copy the
501fbaef 97returned values, but this can make a significant difference when
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98creating references to the returned values.
99
100Keys in the hash are still returned as copies when iterating on
08cd8952 101a hash.
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102
103=item vec(EXPR,OFFSET,BITS) enforces powers-of-two BITS
104
08cd8952 105vec() generates a run-time error if the BITS argument is not
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106a valid power-of-two integer.
107
108=item Text of some diagnostic output has changed
109
110Most references to internal Perl operations in diagnostics
111have been changed to be more descriptive. This may be an
112issue for programs that may incorrectly rely on the exact
113text of diagnostics for proper functioning.
114
115=item C<%@> has been removed
116
117The undocumented special variable C<%@> that used to accumulate
118"background" errors (such as those that happen in DESTROY())
119has been removed, because it could potentially result in memory
120leaks.
121
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122=back
123
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124=head2 C Source Incompatibilities
125
126=over 4
127
128=item C<PERL_POLLUTE>
129
130Release 5.005 grandfathered old global symbol names by providing preprocessor
87275199 131macros for extension source compatibility. As of release 5.6, these
e02fdbd2 132preprocessor definitions are not available by default. You need to explicitly
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133compile perl with C<-DPERL_POLLUTE> to get these definitions. For
134extensions still using the old symbols, this option can be
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135specified via MakeMaker:
136
14218588 137 perl Makefile.PL POLLUTE=1
e02fdbd2 138
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139=item C<PERL_IMPLICIT_CONTEXT>
140
141This new build option provides a set of macros for all API functions
142such that an implicit interpreter/thread context argument is passed to
143every API function. As a result of this, something like C<sv_setsv(foo,bar)>
2c2d71f5 144amounts to a macro invocation that actually translates to something like
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145C<Perl_sv_setsv(my_perl,foo,bar)>. While this is generally expected
146to not have any significant source compatibility issues, the difference
147between a macro and a real function call will need to be considered.
148
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149This means that there B<is> a source compatibility issue as a result of
150this if your extensions attempt to use pointers to any of the Perl API
151functions.
152
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153Note that the above issue is not relevant to the default build of
154Perl, whose interfaces continue to match those of prior versions
155(but subject to the other options described here).
156
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157PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
158with one of -Dusethreads, -Dusemultiplicity, or both.
f29c64d6 159
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160See L<perlguts/"The Perl API"> for detailed information on the
161ramifications of building Perl using this option.
162
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163=item C<PERL_POLLUTE_MALLOC>
164
14218588 165Enabling Perl's malloc in release 5.005 and earlier caused
86058a2d 166the namespace of system versions of the malloc family of functions to
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167be usurped by the Perl versions, since by default they used the
168same names.
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169
170Besides causing problems on platforms that do not allow these functions to
171be cleanly replaced, this also meant that the system versions could not
172be called in programs that used Perl's malloc. Previous versions of Perl
14218588 173have allowed this behaviour to be suppressed with the HIDEMYMALLOC and
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174EMBEDMYMALLOC preprocessor definitions.
175
87275199 176As of release 5.6, Perl's malloc family of functions have default names
86058a2d 177distinct from the system versions. You need to explicitly compile perl with
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178C<-DPERL_POLLUTE_MALLOC> to get the older behaviour. HIDEMYMALLOC
179and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now
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180the default.
181
182Note that these functions do B<not> constitute Perl's memory allocation API.
183See L<perlguts/"Memory Allocation"> for further information about that.
184
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185=back
186
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187=head2 Compatible C Source API Changes
188
189=over
190
191=item C<PATCHLEVEL> is now C<PERL_VERSION>
192
14218588 193The cpp macros C<PERL_REVISION>, C<PERL_VERSION>, and C<PERL_SUBVERSION>
cceca5ed 194are now available by default from perl.h, and reflect the base revision,
14218588 195patchlevel, and subversion respectively. C<PERL_REVISION> had no
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196prior equivalent, while C<PERL_VERSION> and C<PERL_SUBVERSION> were
197previously available as C<PATCHLEVEL> and C<SUBVERSION>.
198
14218588 199The new names cause less pollution of the B<cpp> namespace and reflect what
cceca5ed 200the numbers have come to stand for in common practice. For compatibility,
14218588 201the old names are still supported when F<patchlevel.h> is explicitly
cceca5ed 202included (as required before), so there is no source incompatibility
14218588 203from the change.
cceca5ed 204
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205=item Support for C++ exceptions
206
207change#3386, also needs perlguts documentation
208[TODO - Chip Salzenberg <chip@perlsupport.com>]
209
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210=back
211
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212=head2 Binary Incompatibilities
213
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214The default build of this release is binary compatible with the 5.005
215release or its maintenance versions.
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216
217The usethreads or usemultiplicity builds are B<not> binary compatible
218with the corresponding builds in 5.005.
e02fdbd2 219
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220=head1 Installation and Configuration Improvements
221
222=head2 New Configure flags
223
224The following new flags may be enabled on the Configure command line
225by running Configure with C<-Dflag>.
226
227 usemultiplicity
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228
229 uselongdouble
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230 usemorebits
231 uselargefiles
a5222a85 232
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233=head2 -Dusethreads and -Duse64bits now more daring
234
235The Configure options enabling the use of threads and the use of
23664-bitness are now more daring in the sense that they no more have
237an explicit list of operating systems of known threads/64-bit
238capabilities. In other words: if your operating system has the
239necessary APIs, you should be able just to go ahead and use them.
240See also L<"64-bit support">.
241
242=head2 Long Doubles
243
244Some platforms have "long doubles", floating point numbers of even
437784d6 245larger range than ordinary "doubles". To enable using long doubles for
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246Perl's scalars, use -Duselongdouble.
247
248=head2 -Dusemorebits
249
250You can enable both -Duse64bits and -Dlongdouble by -Dusemorebits.
251See also L<"64-bit support">.
252
253=head2 -Duselargefiles
254
255Some platforms support large files, files larger than two gigabytes.
256See L<"Large file support"> for more information.
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257
258=head2 installusrbinperl
259
260You can use "Configure -Uinstallusrbinperl" which causes installperl
261to skip installing perl also as /usr/bin/perl. This is useful if you
262prefer not to modify /usr/bin for some reason or another but harmful
263because many scripts assume to find Perl in /usr/bin/perl.
264
265=head2 SOCKS support
266
267You can use "Configure -Dusesocks" which causes Perl to probe
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268for the SOCKS (v5, not v4) proxy protocol library,
269http://www.socks.nec.com/
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270
271=head2 C<-A> flag
272
273You can "post-edit" the Configure variables using the Configure C<-A>
274flag. The editing happens immediately after the platform specific
275hints files have been processed but before the actual configuration
276process starts. Run C<Configure -h> to find out the full C<-A> syntax.
277
c35dd67d 278=head2 Enhanced Installation Directories
67d3893f 279
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280The installation structure has been enriched to improve the support for
281maintaining multiple versions of perl, to provide locations for
282vendor-supplied modules and scripts, and to ease maintenance of
283locally-added modules and scripts. See the section on Installation
284Directories in the INSTALL file for complete details. For most users
285building and installing from source, the defaults should be fine.
67d3893f 286
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287=head1 Core Changes
288
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289=head2 Unicode and UTF-8 support
290
291Perl can optionally use UTF-8 as its internal representation for character
a5222a85 292strings. The C<utf8> pragma enables this support in the current lexical
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293scope. See L<utf8> for more information.
294
295=head2 Lexically scoped warning categories
296
297You can now control the granularity of warnings emitted by perl at a finer
4438c4b7 298level using the C<use warnings> pragma. See L<warnings> and L<perllexwarn>
0453d815 299for details.
9d73390d 300
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301=head2 Lvalue subroutines
302
303WARNING: This is an experimental feature.
304
305change#4081
306[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>,
307Tuomas Lukka <lukka@fas.harvard.edu>)]
308
309=head2 "our" declarations
310
311An "our" declaration introduces a value that can be best understood
312as a lexically scoped symbolic alias to a global variable in the
313current package. This is mostly useful as an alternative to the
314C<vars> pragma, but also provides the opportunity to introduce
315typing and other attributes for such variables. See L<perlfunc/our>.
316
317=head2 Weak references
318
319WARNING: This is an experimental feature.
320
321change#3385, also need perlguts documentation
322
323[TODO - Tuomas Lukka <lukka@fas.harvard.edu>]
324
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325=head2 File globbing implemented internally
326
327WARNING: This is currently an experimental feature. Interfaces and
328implementation are likely to change.
329
330Perl can be compiled with -DPERL_INTERNAL_GLOB to use the File::Glob
331implementation of the glob() operator. This avoids using an external
332csh process and the problems associated with it.
333
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334=head2 Binary numbers supported
335
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336Binary numbers are now supported as literals, in s?printf formats, and
337C<oct()>:
338
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339 $answer = 0b101010;
340 printf "The answer is: %b\n", oct("0b101010");
4f19785b 341
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342=head2 Some arrows may be omitted in calls through references
343
344Perl now allows the arrow to be omitted in many constructs
345involving subroutine calls through references. For example,
346C<$foo[10]->('foo')> may now be written C<$foo[10]('foo')>.
347This is rather similar to how the arrow may be omitted from
348C<$foo[10]->{'foo'}>. Note however, that the arrow is still
349required for C<foo(10)->('bar')>.
350
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351=head2 syswrite() ease-of-use
352
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353The length argument of C<syswrite()> has become optional.
354
355=head2 Filehandles can be autovivified
356
357The construct C<open(my $fh, ...)> can be used to create filehandles
358more easily. The filehandle will be automatically closed at the end
359of the scope of $fh, provided there are no other references to it. This
360largely eliminates the need for typeglobs when opening filehandles
361that must be passed around, as in the following example:
362
363 sub myopen {
364 open my $fh, "@_"
365 or die "Can't open '@_': $!";
366 return $fh;
367 }
368
369 {
370 my $f = myopen("</etc/motd");
371 print <$f>;
372 # $f implicitly closed here
373 }
374
375[TODO - this idiom needs more pod penetration]
6c67e1bb 376
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377=head2 64-bit support
378
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379All platforms that have 64-bit integers either (a) natively as longs
380or ints (b) via special compiler flags (c) using long long are able to
381use "quads" (64-integers) as follows:
382
383=over 4
384
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385=item *
386
387constants (decimal, hexadecimal, octal, binary) in the code
388
389=item *
9c107f78 390
a5222a85 391arguments to oct() and hex()
9c107f78 392
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393=item *
394
395arguments to print(), printf() and sprintf() (flag prefixes ll, L, q)
396
397=item *
9c107f78 398
a5222a85 399printed as such
9c107f78 400
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401=item *
402
403pack() and unpack() "q" and "Q" formats
404
405=item *
406
407in basic arithmetics: + - * / %
408
409=item *
1fad5d67 410
a5222a85 411vec() (but see the below note about bit arithmetics)
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412
413=back
414
415Note that unless you have the case (a) you will have to configure
416and compile Perl using the -Duse64bits Configure flag.
417
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418Unfortunately bit arithmetics (&, |, ^, ~, <<, >>) for numbers are not
41964-bit clean, they are explictly forced to be 32-bit. Bit arithmetics
420for bit vectors (created by vec()) are not limited in their width.
d0ba1bd2 421
2d4389e4 422Last but not least: note that due to Perl's habit of always using
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423floating point numbers the quads are still not true integers.
424When quads overflow their limits (0...18_446_744_073_709_551_615 unsigned,
425-9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they
426are silently promoted to floating point numbers, after which they will
427start losing precision (their lower digits).
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428
429=head2 Large file support
430
431If you have filesystems that support "large files" (files larger than
aa855319 4322 gigabytes), you may now also be able to create and access them from
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433Perl. You have to use Configure -Duselargefiles. Turning on the
434large file support turns on also the 64-bit support, for obvious reasons.
2d4389e4 435
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436Note that in addition to requiring a proper file system to do large
437files you may also need to adjust your per-process (or your
438per-system, or per-process-group, or per-user-group) maximum filesize
439limits before running Perl scripts that try to handle large files,
440especially if you intend to write such files.
441
442Finally, in addition to your process/process group maximum filesize
443limits, you may have quota limits on your filesystems that stop you
444(your user id or your user group id) from using large files.
445
446Adjusting your process/user/group/file system/operating system limits
447is outside the scope of Perl core language. For process limits, you
448may try increasing the limits using your shell's limits/limit/ulimit
449command before running Perl. The BSD::Resource extension (not
450included with the standard Perl distribution) may also be of use, it
451offers the getrlimit/setrlimit interface that can be used to adjust
452process resource usage limits, including the maximum filesize limit.
475d79b5 453
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454=head2 Long doubles
455
456In some systems you may be able to use long doubles to enhance the
457range of precision of your double precision floating point numbers
458(that is, Perl's numbers). Use Configure -Duselongdouble to enable
459this support (if it is available).
460
461=head2 "more bits"
462
463You can Configure -Dusemorebits to turn on both the 64-bit support
464and the long double support.
09bef843 465
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466=head2 Better syntax checks on parenthesized unary operators
467
468Expressions such as:
469
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470 print defined(&foo,&bar,&baz);
471 print uc("foo","bar","baz");
472 undef($foo,&bar);
62c18ce2 473
7711098a 474used to be accidentally allowed in earlier versions, and produced
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475unpredictable behaviour. Some produced ancillary warnings
476when used in this way; others silently did the wrong thing.
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477
478The parenthesized forms of most unary operators that expect a single
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479argument now ensure that they are not called with more than one
480argument, making the cases shown above syntax errors. The usual
481behaviour of:
62c18ce2 482
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483 print defined &foo, &bar, &baz;
484 print uc "foo", "bar", "baz";
485 undef $foo, &bar;
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486
487remains unchanged. See L<perlop>.
488
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489=head2 POSIX character class syntax [: :] supported
490
491For example to match alphabetic characters use /[[:alpha:]]/.
492See L<perlre> for details.
493
5a929a98 494=head2 Improved C<qw//> operator
8127e0e3 495
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496The C<qw//> operator is now evaluated at compile time into a true list
497instead of being replaced with a run time call to C<split()>. This
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498removes the confusing misbehaviour of C<qw//> in scalar context, which
499had inherited that behaviour from split().
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500
501Thus:
502
503 $foo = ($bar) = qw(a b c); print "$foo|$bar\n";
504
505now correctly prints "3|a", instead of "2|a".
8127e0e3 506
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507=head2 pack() format 'Z' supported
508
509The new format type 'Z' is useful for packing and unpacking null-terminated
510strings. See L<perlfunc/"pack">.
511
4d0c1c44 512=head2 pack() format modifier '!' supported
ee3907e2 513
14218588 514The new format type modifier '!' is useful for packing and unpacking
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515native shorts, ints, and longs. See L<perlfunc/"pack">.
516
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517=head2 pack() and unpack() support counted strings
518
a5222a85 519The template character '/' can be used to specify a counted string
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520type to be packed or unpacked. See L<perlfunc/"pack">.
521
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522=head2 Comments in pack() templates
523
524The '#' character in a template introduces a comment up to
525end of the line. This facilitates documentation of pack()
526templates.
527
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528=head2 $^X variables may now have names longer than one character
529
530Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax
531error. Now variable names that begin with a control character may be
532arbitrarily long. However, for compatibility reasons, these variables
533I<must> be written with explicit braces, as C<${^XY}> for example.
14218588 534C<${^XYZ}> is synonymous with ${"\cXYZ"}. Variable names with more
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535than one control character, such as C<${^XY^Z}>, are illegal.
536
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537The old syntax has not changed. As before, `^X' may be either a
538literal control-X character or the two-character sequence `caret' plus
539`X'. When braces are omitted, the variable name stops after the
2b92dfce 540control character. Thus C<"$^XYZ"> continues to be synonymous with
7711098a 541C<$^X . "YZ"> as before.
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542
543As before, lexical variables may not have names beginning with control
544characters. As before, variables whose names begin with a control
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545character are always forced to be in package `main'. All such variables
546are reserved for future extensions, except those that begin with
09bef843 547C<^_>, which may be used by user programs and are guaranteed not to
14218588 548acquire special meaning in any future version of Perl.
2b92dfce 549
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550=head2 C<use attrs> implicit in subroutine attributes
551
552Formerly, if you wanted to mark a subroutine as being a method call or
553as requiring an automatic lock() when it is entered, you had to declare
554that with a C<use attrs> pragma in the body of the subroutine.
555That can now be accomplished with a declaration syntax, like this:
556
557 sub mymethod : locked, method ;
558 ...
559 sub mymethod : locked, method {
560 ...
561 }
562
563F<AutoSplit.pm> and F<SelfLoader.pm> have been updated to keep the attributes
564with the stubs they provide. See L<attributes>.
565
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566=head2 Regular expression improvements
567
568change#2827,2373,2372,2365,1813,1800,4112,4158,4215,4301
569[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
570
571=head2 Overloading improvements
572
573change#2150
574[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
575
576=head2 open() with more than two arguments
577
578[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
579
580=head2 Support for interpolating named characters
581
582change#4052
583[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
584
08cd8952 585=head2 Experimental support for user-hooks in @INC
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586
587[TODO - Ken Fox <kfox@ford.com>]
588
589=head2 C<require> and C<do> may be overridden
590
591C<require> and C<do 'file'> operations may be overridden locally
592by importing subroutines of the same name into the current package
593(or globally by importing them into the CORE::GLOBAL:: namespace).
594Overriding C<require> will also affect C<use>, provided the override
595is visible at compile-time.
596See L<perlsub/"Overriding Built-in Functions">.
597
598=head2 New variable $^C reflects C<-c> switch
599
08cd8952 600C<$^C> has a boolean value that reflects whether perl is being run
a5222a85
GS
601in compile-only mode (i.e. via the C<-c> switch). Since
602BEGIN blocks are executed under such conditions, this variable
603enables perl code to determine whether actions that make sense
604only during normal running are warranted. See L<perlvar>.
605
606=head2 Optional Y2K warnings
607
608If Perl is built with the cpp macro C<PERL_Y2KWARN> defined,
609it emits optional warnings when concatenating the number 19
610with another number.
611
612This behavior must be specifically enabled when running Configure.
613See L<INSTALL> and L<README.Y2K>.
614
fbad3eb5
GS
615=head1 Significant bug fixes
616
617=head2 E<lt>HANDLEE<gt> on empty files
618
619With C<$/> set to C<undef>, slurping an empty file returns a string of
14218588
GS
620zero length (instead of C<undef>, as it used to) the first time the
621HANDLE is read. Further reads yield C<undef>.
fbad3eb5
GS
622
623This means that the following will append "foo" to an empty file (it used
14218588 624to do nothing):
fbad3eb5
GS
625
626 perl -0777 -pi -e 's/^/foo/' empty_file
627
14218588 628The behaviour of:
fbad3eb5
GS
629
630 perl -pi -e 's/^/foo/' empty_file
631
632is unchanged (it continues to leave the file empty).
633
0244c3a4
GS
634=head2 C<eval '...'> improvements
635
636Line numbers (as reflected by caller() and most diagnostics) within
637C<eval '...'> were often incorrect when here documents were involved.
638This has been corrected.
639
640Lexical lookups for variables appearing in C<eval '...'> within
641functions that were themselves called within an C<eval '...'> were
14218588
GS
642searching the wrong place for lexicals. The lexical search now
643correctly ends at the subroutine's block boundary.
0244c3a4
GS
644
645Parsing of here documents used to be flawed when they appeared as
646the replacement expression in C<eval 's/.../.../e'>. This has
647been fixed.
648
a5222a85
GS
649=head2 All compilation errors are true errors
650
651Some "errors" encountered at compile time were by neccessity
652generated as warnings followed by eventual termination of the
653program. This enabled more such errors to be reported in a
654single run, rather than causing a hard stop at the first error
655that was encountered.
656
657The mechanism for reporting such errors has been reimplemented
658to queue compile-time errors and report them at the end of the
659compilation as true errors rather than as warnings. This fixes
08cd8952
GS
660cases where error messages leaked through in the form of warnings
661when code was compiled at run time using C<eval STRING>, and
662also allows such errors to be reliably trapped using __DIE__ hooks.
a5222a85 663
45bc9206
GS
664=head2 Automatic flushing of output buffers
665
14218588
GS
666fork(), exec(), system(), qx//, and pipe open()s now flush buffers
667of all files opened for output when the operation
668was attempted. This mostly eliminates confusing
45bc9206 669buffering mishaps suffered by users unaware of how Perl internally
14218588 670handles I/O.
45bc9206 671
af8c498a
GS
672=head2 Better diagnostics on meaningless filehandle operations
673
674Constructs such as C<open(E<lt>FHE<gt>)> and C<close(E<lt>FHE<gt>)>
675are compile time errors. Attempting to read from filehandles that
676were opened only for writing will now produce warnings (just as
677writing to read-only filehandles does).
678
a5222a85
GS
679=head2 Where possible, buffered data discarded from duped input filehandle
680
681C<open(NEW, "E<lt>&OLD")> now attempts to discard any data that
682was previously read and buffered in C<OLD> before duping the handle.
683On platforms where doing this is allowed, the next read operation
684on C<NEW> will return the same data as the corresponding operation
685on C<OLD>. Formerly, it would have returned the data from the start
686of the following disk block instead.
687
688=head2 system(), backticks and pipe open now reflect exec() failure
689
690On Unix and similar platforms, system(), qx() and open(FOO, "cmd |")
691etc., are implemented via fork() and exec(). When the underlying
692exec() fails, earlier versions did not report the error properly,
693since the exec() happened to be in a different process.
694
695The child process now communicates with the parent about the
437784d6 696error in launching the external command, which allows these
a5222a85
GS
697constructs to return with their usual error value and set $!.
698
699=head2 Implicitly closed filehandles are safer
700
701Sometimes implicitly closed filehandles (as when they are localized,
702and Perl automatically closes them on exiting the scope) could
703inadvertently set $? or $!. This has been corrected.
704
705=head2 C<(\$)> prototype and C<$foo{a}>
706
707An scalar reference prototype now correctly allows a hash or
708array element in that slot.
709
710=head2 Pseudo-hashes work better
711
712Dereferencing some types of reference values in a pseudo-hash,
713such as C<$ph->{foo}[1]>, was accidentally disallowed. This has
714been corrected.
715
716When applied to a pseudo-hash element, exists() now reports whether
717the specified value exists, not merely if the key is valid.
718
719=head2 C<goto &sub> and AUTOLOAD
720
08cd8952 721The C<goto &sub> construct works correctly when C<&sub> happens
a5222a85
GS
722to be autoloaded.
723
724=head2 C<-bareword> allowed under C<use integer>
725
726The autoquoting of barewords preceded by C<-> did not work
727in prior versions when the C<integer> pragma was enabled.
728This has been fixed.
729
730=head2 Boolean assignment operators are legal lvalues
731
732Constructs such as C<($a ||= 2) += 1> are now allowed.
733
734=head2 C<sort $coderef @foo> allowed
735
736sort() did not accept a subroutine reference as the comparison
08cd8952 737function in earlier versions. This is now permitted.
a5222a85
GS
738
739=head2 Failures in DESTROY()
740
741When code in a destructor threw an exception, it went unnoticed
742in earlier versions of Perl, unless someone happened to be
743looking in $@ just after the point the destructor happened to
744run. Such failures are now visible as warnings when warnings are
745enabled.
746
747=head2 Locale bugs fixed
54195c32 748
437784d6 749printf() and sprintf() previously reset the numeric locale
67d3893f
JH
750back to the default "C" locale. This has been fixed.
751
752Numbers formatted according to the local numeric locale
753(such as using a decimal comma instead of a decimal dot) caused
754"isn't numeric" warnings, even while the operations accessing
755those numbers produced correct results. The warnings are gone.
54195c32 756
a5222a85
GS
757=head2 Memory leaks
758
759The C<eval 'return sub {...}'> construct could sometimes leak
760memory. This has been fixed.
761
762Operations that aren't filehandle constructors used to leak memory
763when used on invalid filehandles. This has been fixed.
764
765Constructs that modified C<@_> could fail to deallocate values
766in C<@_> and thus leak memory. This has been corrected.
767
768=head2 Spurious subroutine stubs after failed subroutine calls
769
770Perl could sometimes create empty subroutine stubs when a
771subroutine was not found in the package. Such cases stopped
772later method lookups from progressing into base packages.
773This has been corrected.
774
775=head2 Consistent numeric conversions
776
777change#3378,3318
778[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
779
780=head2 Taint failures under C<-U>
781
782When running in unsafe mode, taint violations could sometimes
783cause silent failures. This has been fixed.
784
785=head2 END blocks and the C<-c> switch
786
787Prior versions used to run BEGIN B<and> END blocks when Perl was
788run in compile-only mode. Since this is typically not the expected
08cd8952 789behavior, END blocks are not executed anymore when the C<-c> switch
a5222a85
GS
790is used.
791
792Note that something resembling the previous behavior can still be
f5daac4a 793obtained by putting C<BEGIN { $^C = 0; exit; }> at the very end of
a5222a85
GS
794the top level source file.
795
796=head2 Potential to leak DATA filehandles
797
798Using the C<__DATA__> token creates an implicit filehandle to
799the file that contains the token. It is the program's
800responsibility to close it when it is done reading from it.
801
802This caveat is now better explained in the documentation.
803See L<perldata>.
804
805=head2 Diagnostics follow STDERR
806
807Diagnostic output now goes to whichever file the C<STDERR> handle
808is pointing at, instead of always going to the underlying C runtime
809library's C<stderr>.
810
811=head2 Other fixes for better diagnostics
812
437784d6 813Line numbers are no longer suppressed (under most likely circumstances)
a5222a85
GS
814during the global destruction phase.
815
816Diagnostics emitted from code running in threads other than the main
817thread are now accompanied by the thread ID.
818
819Embedded null characters in diagnostics now actually show up. They
820used to truncate the message in prior versions.
821
822$foo::a and $foo::b are now exempt from "possible typo" warnings only
823if sort() is encountered in package foo.
824
501fbaef 825Unrecognized alphabetic escapes encountered when parsing quote
a5222a85
GS
826constructs now generate a warning, since they may take on new
827semantics in later versions of Perl.
828
829=head1 Performance enhancements
830
831=head2 Simple sort() using { $a <=> $b } and the like are optimized
832
08cd8952 833Many common sort() operations using a simple inlined block are now
a5222a85
GS
834optimized for faster performance.
835
836=head2 Optimized assignments to lexical variables
837
838Certain operations in the RHS of assignment statements have been
839optimized to directly set the lexical variable on the LHS,
840eliminating redundant copying overheads.
841
842=head2 Method lookups optimized
843
844[TODO - Chip Salzenberg <chip@perlsupport.com>]
845
846=head2 Faster mechanism to invoke XSUBs
847
848change#4044,4125
849[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
850
851=head2 Perl_malloc() improvements
852
853change#4237
854[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
855
856=head2 Faster subroutine calls
857
858Minor changes in how subroutine calls are handled internally
859provide marginal improvements in performance.
860
861=head1 Platform specific changes
862
863=head2 Additional supported platforms
ba8251e8 864
5fdc711f
GS
865=over 4
866
867=item *
868
6c67e1bb
TC
869VM/ESA is now supported.
870
5fdc711f
GS
871=item *
872
ee3907e2
JH
873Siemens BS2000 is now supported under the POSIX Shell.
874
875=item *
876
2bb14304
JH
877The Mach CThreads (NEXTSTEP, OPENSTEP) are now supported by the Thread
878extension.
6c67e1bb 879
5fdc711f
GS
880=item *
881
ee3907e2 882GNU/Hurd is now supported.
6c67e1bb 883
00ad96e1
JH
884=item *
885
886Rhapsody is now supported.
887
27806c82
JH
888=item *
889
890EPOC is is now supported (on Psion 5).
891
5fdc711f
GS
892=back
893
a5222a85
GS
894=head2 DOS
895
896[TODO - Laszlo Molnar <laszlo.molnar@eth.ericsson.se>]
897
898=head2 OS/2
899
900[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
901
902=head2 VMS
903
904[TODO - Charles Bailey <bailey@newman.upenn.edu>]
905
906=head2 Win32
907
908Site library searches failed to look for ".../site/5.XXX/lib"
909if ".../site/5.XXXYY/lib" wasn't found. This has been corrected.
910
911When given a pathname that consists only of a drivename, such
912as C<A:>, opendir() and stat() now use the current working
913directory for the drive rather than the drive root.
914
915The builtin XSUB functions in the Win32:: namespace are
916documented. See L<Win32>.
917
918$^X now contains the full path name of the running executable.
919
920A Win32::GetLongPathName() function is provided to complement
921Win32::GetFullPathName() and Win32::GetShortPathName(). See L<Win32>.
922
923POSIX::uname() is supported.
924
925system(1,...) now returns true process IDs rather than process
926handles. kill() accepts any real process id, rather than strictly
927return values from system(1,...).
928
929The C<Shell> module is supported.
930
883d36a6
GS
931Rudimentary support for building under command.com in Windows 95
932has been added.
933
a5222a85
GS
934[TODO - GSAR]
935
6c67e1bb
TC
936=head1 New tests
937
938=over 4
939
09bef843
SB
940=item lib/attrs
941
942Compatibility tests for C<sub : attrs> vs the older C<use attrs>.
943
944=item lib/io_const
6c67e1bb
TC
945
946IO constants (SEEK_*, _IO*).
14218588 947
09bef843 948=item lib/io_dir
6c67e1bb
TC
949
950Directory-related IO methods (new, read, close, rewind, tied delete).
951
09bef843 952=item lib/io_multihomed
6c67e1bb
TC
953
954INET sockets with multi-homed hosts.
955
09bef843 956=item lib/io_poll
6c67e1bb
TC
957
958IO poll().
959
09bef843 960=item lib/io_unix
6c67e1bb
TC
961
962UNIX sockets.
963
09bef843
SB
964=item op/attrs
965
966Regression tests for C<my ($x,@y,%z) : attrs> and <sub : attrs>.
967
6c67e1bb
TC
968=item op/filetest
969
970File test operators.
971
972=item op/lex_assign
973
5fdc711f 974Verify operations that access pad objects (lexicals and temporaries).
6c67e1bb
TC
975
976=back
e02fdbd2 977
ba8251e8
GS
978=head1 Modules and Pragmata
979
3e8c4fa0
JH
980=head2 Modules
981
b7d8191e
JH
982=over 4
983
09bef843
SB
984=item attributes
985
986While used internally by Perl as a pragma, this module also
987provides a way to fetch subroutine and variable attributes.
988See L<attributes>.
989
a5222a85
GS
990=item B
991
501fbaef
GS
992The Perl Compiler suite has been extensively reworked for this
993release.
994
a5222a85
GS
995[TODO - Vishal Bhatia <vishal@gol.com>,
996Nick Ing-Simmons <nick@ni-s.u-net.com>]
997
f29c64d6
GS
998=item ByteLoader
999
a5222a85 1000The ByteLoader is a dedicated extension to generate and run
f29c64d6
GS
1001Perl bytecode. See L<ByteLoader>.
1002
a5222a85
GS
1003=item constant
1004
1005References can now be used. See L<constant>.
1006
1007=item charnames
1008
1009change#4052
1010[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1011
1012=item Data::Dumper
1013
1014A C<Maxdepth> setting can be specified to avoid venturing
73b437c8 1015too deeply into deep data structures. See L<Data::Dumper>.
a5222a85
GS
1016
1017Dumping C<qr//> objects works correctly.
1018
1019=item DB
1020
1021C<DB> is an experimental module that exposes a clean abstraction
1022to Perl's debugging API.
1023
1024=item DB_File
1025
1026[TODO - Paul Marquess <paul.marquess@bt.com>]
1027
f29c64d6
GS
1028=item Devel::DProf
1029
9e107c59
GS
1030Devel::DProf, a Perl source code profiler has been added. See
1031L<Devel::DProf> and L<dprofpp>.
f29c64d6 1032
b7d8191e
JH
1033=item Dumpvalue
1034
437784d6 1035The Dumpvalue module provides screen dumps of Perl data.
b7d8191e
JH
1036
1037=item Benchmark
1038
54e82ce5
GS
1039Overall, Benchmark results exhibit lower average error and better timing
1040accuracy.
1041
868cb350 1042You can now run tests for I<n> seconds instead of guessing the right
14218588
GS
1043number of tests to run: e.g. timethese(-5, ...) will run each
1044code for at least 5 CPU seconds. Zero as the "number of repetitions"
155776c0 1045means "for at least 3 CPU seconds". The output format has also
14218588 1046changed. For example:
155776c0 1047
54e82ce5 1048 use Benchmark;$x=3;timethese(-5,{a=>sub{$x*$x},b=>sub{$x**2}})
155776c0
JH
1049
1050will now output something like this:
1051
54e82ce5
GS
1052 Benchmark: running a, b, each for at least 5 CPU seconds...
1053 a: 5 wallclock secs ( 5.77 usr + 0.00 sys = 5.77 CPU) @ 200551.91/s (n=1156516)
1054 b: 4 wallclock secs ( 5.00 usr + 0.02 sys = 5.02 CPU) @ 159605.18/s (n=800686)
155776c0
JH
1055
1056New features: "each for at least N CPU seconds...", "wallclock secs",
1057and the "@ operations/CPU second (n=operations)".
b7d8191e 1058
54e82ce5
GS
1059timethese() now returns a reference to a hash of Benchmark objects containing
1060the test results, keyed on the names of the tests.
1061
1062timethis() now returns the iterations field in the Benchmark result object
1063instead of 0.
1064
1065timethese(), timethis(), and the new cmpthese() (see below) can also take
1066a format specifier of 'none' to suppress output.
1067
1068A new function countit() is just like timeit() except that it takes a
1069TIME instead of a COUNT.
1070
1071A new function cmpthese() prints a chart comparing the results of each test
1072returned from a timethese() call. For each possible pair of tests, the
1073percentage speed difference (iters/sec or seconds/iter) is shown.
1074
1075For other details, see L<Benchmark>.
a5222a85 1076
f505c983
GS
1077=item Devel::Peek
1078
1079The Devel::Peek module provides access to the internal representation
14218588 1080of Perl variables and data. It is a data debugging tool for the XS programmer.
f505c983 1081
a5222a85
GS
1082=item ExtUtils::MakeMaker
1083
1084change#4135, also needs docs in module pod
1085[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
1086
b7d8191e
JH
1087=item Fcntl
1088
1089More Fcntl constants added: F_SETLK64, F_SETLKW64, O_LARGEFILE for
14218588 1090large (more than 4G) file access (64-bit support is not yet
b7d8191e
JH
1091working, though, so no need to get overly excited), Free/Net/OpenBSD
1092locking behaviour flags F_FLOCK, F_POSIX, Linux F_SHLCK, and
1093O_ACCMODE: the mask of O_RDONLY, O_WRONLY, and O_RDWR.
1094
a5222a85
GS
1095=item File::Compare
1096
1097A compare_text() function has been added, which allows custom
1098comparison functions. See L<File::Compare>.
1099
1100=item File::Find
1101
1102File::Find now works correctly when the wanted() function is either
1103autoloaded or is a symbolic reference.
1104
08cd8952 1105A bug that caused File::Find to lose track of the working directory
a5222a85
GS
1106when pruning top-level directories has been fixed.
1107
becf2bd3
GS
1108=item File::Glob
1109
1110This extension implements BSD-style file globbing. It will also be
1111used for the internal implementation of the glob() operator if
1112Perl was compiled with -DPERL_INTERNAL_GLOB. See L<File::Glob>.
1113
f505c983
GS
1114=item File::Spec
1115
1116New methods have been added to the File::Spec module: devnull() returns
19799a22 1117the name of the null device (/dev/null on Unix) and tmpdir() the name of
14218588 1118the temp directory (normally /tmp on Unix). There are now also methods
f505c983 1119to convert between absolute and relative filenames: abs2rel() and
14218588
GS
1120rel2abs(). For compatibility with operating systems that specify volume
1121names in file paths, the splitpath(), splitdir(), and catdir() methods
f505c983
GS
1122have been added.
1123
1124=item File::Spec::Functions
1125
1126The new File::Spec::Functions modules provides a function interface
14218588 1127to the File::Spec module. Allows shorthand
f505c983 1128
14218588 1129 $fullname = catfile($dir1, $dir2, $file);
f505c983
GS
1130
1131instead of
1132
14218588 1133 $fullname = File::Spec->catfile($dir1, $dir2, $file);
f505c983 1134
a5222a85
GS
1135=item Getopt::Long
1136
c6edd1b7
GS
1137Getopt::Long licensing has changed to allow the Perl Artistic License
1138as well as the GPL. It used to be GPL only, which got in the way of
1139non-GPL applications that wanted to use Getopt::Long.
1140
1141Getopt::Long encourages the use of Pod::Usage to produce help
1142messages. For example:
1143
1144 use Getopt::Long;
1145 use Pod::Usage;
1146 my $man = 0;
1147 my $help = 0;
1148 GetOptions('help|?' => \$help, man => \$man) or pod2usage(2);
1149 pod2usage(1) if $help;
1150 pod2usage(-exitstatus => 0, -verbose => 2) if $man;
1151
1152 __END__
1153
1154 =head1 NAME
1155
1156 sample - Using GetOpt::Long and Pod::Usage
1157
1158 =head1 SYNOPSIS
1159
1160 sample [options] [file ...]
1161
1162 Options:
1163 -help brief help message
1164 -man full documentation
1165
1166 =head1 OPTIONS
1167
1168 =over 8
1169
1170 =item B<-help>
1171
1172 Print a brief help message and exits.
1173
1174 =item B<-man>
1175
1176 Prints the manual page and exits.
1177
1178 =back
1179
1180 =head1 DESCRIPTION
1181
1182 B<This program> will read the given input file(s) and do someting
1183 useful with the contents thereof.
1184
1185 =cut
1186
1187See L<Pod::Usage> for details.
1188
1189A bug that prevented the non-option call-back E<lt>E<gt> from being
1190specified as the first argument has been fixed.
1191
1192To specify the characters E<lt> and E<gt> as option starters, use
1193E<gt>E<lt>. Note, however, that changing option starters is strongly
1194deprecated.
a5222a85
GS
1195
1196=item IO
1197
1198write() and syswrite() will now accept a single-argument
1199form of the call, for consistency with Perl's syswrite().
1200
1201You can now create a TCP-based IO::Socket::INET without forcing
1202a connect attempt. This allows you to configure its options
1203(like making it non-blocking) and then call connect() manually.
1204
1205A bug that prevented the IO::Socket::protocol() accessor
1206from ever returning the correct value has been corrected.
1207
1208=item JPL
1209
1210Java Perl Lingo is now distributed with Perl. See jpl/README
1211for more information.
1212
883d36a6
GS
1213=item lib
1214
1215C<use lib> now weeds out any trailing duplicate entries.
1216C<no lib> removes all named entries.
1217
e16b8f49
WM
1218=item Math::BigInt
1219
437784d6 1220The bitwise operations C<E<lt>E<lt>>, C<E<gt>E<gt>>, C<&>, C<|>,
e16b8f49
WM
1221and C<~> are now supported on bigints.
1222
b7d8191e 1223=item Math::Complex
7711098a 1224
14218588 1225The accessor methods Re, Im, arg, abs, rho, and theta can now also
868cb350 1226act as mutators (accessor $z->Re(), mutator $z->Re(3)).
b7d8191e
JH
1227
1228=item Math::Trig
1229
14218588
GS
1230A little bit of radial trigonometry (cylindrical and spherical),
1231radial coordinate conversions, and the great circle distance were added.
b7d8191e 1232
a5222a85
GS
1233=item Pod::Parser
1234
1235[TODO - Brad Appleton <bradapp@enteract.com>]
1236
1237=item Pod::Text and Pod::Man
1238
1239[TODO - Russ Allbery <rra@stanford.edu>]
1240
f4b9d880
RA
1241=item SDBM_File
1242
1243An EXISTS method has been added to this module (and sdbm_exists() has
1244been added to the underlying sdbm library), so one can now call exists
14218588 1245on an SDBM_File tied hash and get the correct result, rather than a
f4b9d880
RA
1246runtime error.
1247
a5222a85
GS
1248A bug that may have caused data loss when more than one disk block
1249happens to be read from the database in a single FETCH() has been
1250fixed.
1251
06ef4121
PC
1252=item Time::Local
1253
1254The timelocal() and timegm() functions used to silently return bogus
437784d6 1255results when the date fell outside the machine's integer range. They
a5222a85 1256now consistently croak() if the date falls in an unsupported range.
06ef4121 1257
8fe0a5c4
JD
1258=item Win32
1259
1260The error return value in list context has been changed for all functions
14218588
GS
1261that return a list of values. Previously these functions returned a list
1262with a single element C<undef> if an error occurred. Now these functions
1263return the empty list in these situations. This applies to the following
8fe0a5c4
JD
1264functions:
1265
14218588
GS
1266 Win32::FsType
1267 Win32::GetOSVersion
8fe0a5c4
JD
1268
1269The remaining functions are unchanged and continue to return C<undef> on
1270error even in list context.
1271
1272The Win32::SetLastError(ERROR) function has been added as a complement
1273to the Win32::GetLastError() function.
1274
1275The new Win32::GetFullPathName(FILENAME) returns the full absolute
14218588
GS
1276pathname for FILENAME in scalar context. In list context it returns
1277a two-element list containing the fully qualified directory name and
501fbaef 1278the filename. See L<Win32>.
8fe0a5c4 1279
9fe6733a
PM
1280=item DBM Filters
1281
1282A new feature called "DBM Filters" has been added to all the
14218588
GS
1283DBM modules--DB_File, GDBM_File, NDBM_File, ODBM_File, and SDBM_File.
1284DBM Filters add four new methods to each DBM module:
9fe6733a
PM
1285
1286 filter_store_key
1287 filter_store_value
1288 filter_fetch_key
1289 filter_fetch_value
1290
14218588 1291These can be used to filter key-value pairs before the pairs are
9fe6733a
PM
1292written to the database or just after they are read from the database.
1293See L<perldbmfilter> for further information.
1294
b7d8191e 1295=back
3e8c4fa0
JH
1296
1297=head2 Pragmata
1298
437784d6 1299C<use attrs> is now obsolete, and is only provided for
09bef843
SB
1300backward-compatibility. It's been replaced by the C<sub : attributes>
1301syntax. See L<perlsub/"Subroutine Attributes"> and L<attributes>.
1302
14218588 1303C<use utf8> to enable UTF-8 and Unicode support.
43165c05
GS
1304
1305C<use caller 'encoding'> allows modules to inherit pragmatic attributes
1306from the caller's context. C<encoding> is currently the only supported
1307attribute.
9d73390d 1308
4438c4b7 1309Lexical warnings pragma, C<use warnings;>, to control optional warnings.
a5222a85 1310See L<perllexwarn>.
6c67e1bb 1311
67d3893f
JH
1312C<use filetest> to control the behaviour of filetests (C<-r> C<-w>
1313...). Currently only one subpragma implemented, "use filetest
1314'access';", that uses access(2) or equivalent to check permissions
1315instead of using stat(2) as usual. This matters in filesystems
1316where there are ACLs (access control lists): the stat(2) might lie,
1317but access(2) knows better.
6c67e1bb 1318
ba8251e8
GS
1319=head1 Utility Changes
1320
a5222a85
GS
1321=head2 h2ph
1322
1323[TODO - Kurt Starsinic <kstar@chapin.edu>]
1324
1325=head2 perlcc
1326
1327C<perlcc> now supports the C and Bytecode backends. By default,
1328it generates output from the simple C backend rather than the
1329optimized C backend.
1330
1331Support for non-Unix platforms has been improved.
1332
1333=head2 h2xs
1334
1335change#4232
1336[TODO - Ilya Zakharevich <ilya@math.ohio-state.edu>]
e02fdbd2 1337
ba8251e8
GS
1338=head1 Documentation Changes
1339
5fdc711f
GS
1340=over 4
1341
883d36a6
GS
1342=item perlcompile.pod
1343
1344An introduction to using the Perl Compiler suite.
1345
c7c04614
GS
1346=item perlfilter.pod
1347
1348An introduction to writing Perl source filters.
1349
883d36a6
GS
1350=item perlhack.pod
1351
1352Some guidelines for hacking the Perl source code.
1353
5fdc711f 1354=item perlopentut.pod
f8284313 1355
5fdc711f
GS
1356A tutorial on using open() effectively.
1357
1358=item perlreftut.pod
1359
1360A tutorial that introduces the essentials of references.
1361
14218588
GS
1362=item perltootc.pod
1363
1364A tutorial on managing class data for object modules.
1365
5fdc711f 1366=back
e02fdbd2 1367
73b437c8 1368=head1 New or Changed Diagnostics
ba8251e8 1369
a99ba403
GS
1370=over 4
1371
09bef843
SB
1372=item "my sub" not yet implemented
1373
1374(F) Lexically scoped subroutines are not yet implemented. Don't try that
1375yet.
1376
a99ba403
GS
1377=item '!' allowed only after types %s
1378
1379(F) The '!' is allowed in pack() and unpack() only after certain types.
1380See L<perlfunc/pack>.
1381
1382=item / cannot take a count
1383
1384(F) You had an unpack template indicating a counted-length string,
1385but you have also specified an explicit size for the string.
1386See L<perlfunc/pack>.
1387
1388=item / must be followed by a, A or Z
1389
1390(F) You had an unpack template indicating a counted-length string,
1391which must be followed by one of the letters a, A or Z
1392to indicate what sort of string is to be unpacked.
1393See L<perlfunc/pack>.
1394
1395=item / must be followed by a*, A* or Z*
1396
437784d6 1397(F) You had a pack template indicating a counted-length string,
a99ba403
GS
1398Currently the only things that can have their length counted are a*, A* or Z*.
1399See L<perlfunc/pack>.
1400
1401=item / must follow a numeric type
1402
1403(F) You had an unpack template that contained a '#',
1404but this did not follow some numeric unpack specification.
1405See L<perlfunc/pack>.
1406
1407=item Repeat count in pack overflows
1408
1409(F) You can't specify a repeat count so large that it overflows
1410your signed integers. See L<perlfunc/pack>.
1411
1412=item Repeat count in unpack overflows
1413
1414(F) You can't specify a repeat count so large that it overflows
1415your signed integers. See L<perlfunc/unpack>.
1416
1417=item /%s/: Unrecognized escape \\%c passed through
1418
1419(W) You used a backslash-character combination which is not recognized
1420by Perl. This combination appears in an interpolated variable or a
1028017a
JH
1421C<'>-delimited regular expression. The character was understood literally.
1422
1423=item /%s/: Unrecognized escape \\%c in character class passed through
1424
1425(W) You used a backslash-character combination which is not recognized
1426by Perl inside character classes. The character was understood literally.
a99ba403
GS
1427
1428=item /%s/ should probably be written as "%s"
1429
1430(W) You have used a pattern where Perl expected to find a string,
437784d6 1431as in the first argument to C<join>. Perl will treat the true
a99ba403
GS
1432or false result of matching the pattern against $_ as the string,
1433which is probably not what you had in mind.
1434
1435=item %s() called too early to check prototype
1436
1437(W) You've called a function that has a prototype before the parser saw a
1438definition or declaration for it, and Perl could not check that the call
1439conforms to the prototype. You need to either add an early prototype
1440declaration for the subroutine in question, or move the subroutine
1441definition ahead of the call to get proper prototype checking. Alternatively,
1442if you are certain that you're calling the function correctly, you may put
1443an ampersand before the name to avoid the warning. See L<perlsub>.
1444
09bef843
SB
1445=item %s package attribute may clash with future reserved word: %s
1446
1447(W) A lowercase attribute name was used that had a package-specific handler.
1448That name might have a meaning to Perl itself some day, even though it
1449doesn't yet. Perhaps you should use a mixed-case attribute name, instead.
1450See L<attributes>.
1451
a99ba403 1452=item (in cleanup) %s
6b121555 1453
a99ba403
GS
1454(W) This prefix usually indicates that a DESTROY() method raised
1455the indicated exception. Since destructors are usually called by
1456the system at arbitrary points during execution, and often a vast
1457number of times, the warning is issued only once for any number
1458of failures that would otherwise result in the same message being
1459repeated.
1460
1461Failure of user callbacks dispatched using the C<G_KEEPERR> flag
1462could also result in this warning. See L<perlcall/G_KEEPERR>.
1463
1464=item <> should be quotes
1465
1466(F) You wrote C<require E<lt>fileE<gt>> when you should have written
1467C<require 'file'>.
1468
1469=item Attempt to join self
1470
1471(F) You tried to join a thread from within itself, which is an
1472impossible task. You may be joining the wrong thread, or you may
1473need to move the join() to some other thread.
1474
1475=item Bad evalled substitution pattern
1476
1477(F) You've used the /e switch to evaluate the replacement for a
1478substitution, but perl found a syntax error in the code to evaluate,
1479most likely an unexpected right brace '}'.
1480
1481=item Bad realloc() ignored
1482
1483(S) An internal routine called realloc() on something that had never been
1484malloc()ed in the first place. Mandatory, but can be disabled by
1485setting environment variable C<PERL_BADFREE> to 1.
1486
1487=item Binary number > 0b11111111111111111111111111111111 non-portable
1488
1489(W) The binary number you specified is larger than 2**32-1
1490(4294967295) and therefore non-portable between systems. See
1491L<perlport> for more on portability concerns.
1492
1493=item Bit vector size > 32 non-portable
1494
1495(W) Using bit vector sizes larger than 32 is non-portable.
1496
1497=item Buffer overflow in prime_env_iter: %s
1498
1499(W) A warning peculiar to VMS. While Perl was preparing to iterate over
1500%ENV, it encountered a logical name or symbol definition which was too long,
1501so it was truncated to the string shown.
1502
1503=item Can't check filesystem of script "%s"
1504
1505(P) For some reason you can't check the filesystem of the script for nosuid.
1506
1507=item Can't modify non-lvalue subroutine call
1508
437784d6
GS
1509(F) Subroutines meant to be used in lvalue context should be declared as
1510such, see L<perlsub/"Lvalue subroutines">.
a99ba403
GS
1511
1512=item Can't read CRTL environ
1513
1514(S) A warning peculiar to VMS. Perl tried to read an element of %ENV
1515from the CRTL's internal environment array and discovered the array was
1516missing. You need to figure out where your CRTL misplaced its environ
1517or define F<PERL_ENV_TABLES> (see L<perlvms>) so that environ is not searched.
1518
1519=item Can't remove %s: %s, skipping file
1520
1521(S) You requested an inplace edit without creating a backup file. Perl
1522was unable to remove the original file to replace it with the modified
1523file. The file was left unmodified.
1524
1525=item Can't return %s from lvalue subroutine
1526
1527(F) Perl detected an attempt to return illegal lvalues (such
1528as temporary or readonly values) from a subroutine used as an lvalue.
1529This is not allowed.
1530
1531=item Can't weaken a nonreference
1532
1533(F) You attempted to weaken something that was not a reference. Only
1534references can be weakened.
1535
1536=item Character class [:%s:] unknown
1537
1538(F) The class in the character class [: :] syntax is unknown.
437784d6 1539See L<perlre>.
a99ba403
GS
1540
1541=item Character class syntax [%s] belongs inside character classes
1542
1543(W) The character class constructs [: :], [= =], and [. .] go
1544I<inside> character classes, the [] are part of the construct,
437784d6
GS
1545for example: /[012[:alpha:]345]/. Note that [= =] and [. .]
1546are not currently implemented; they are simply placeholders for
1547future extensions.
a99ba403
GS
1548
1549=item Constant is not %s reference
1550
1551(F) A constant value (perhaps declared using the C<use constant> pragma)
1552is being dereferenced, but it amounts to the wrong type of reference. The
1553message indicates the type of reference that was expected. This usually
1554indicates a syntax error in dereferencing the constant value.
1555See L<perlsub/"Constant Functions"> and L<constant>.
1556
1557=item constant(%s): %%^H is not localized
1558
1559(F) When setting compile-time-lexicalized hash %^H one should set the
1560corresponding bit of $^H as well.
1561
1562=item constant(%s): %s
1563
1564(F) Compile-time-substitutions (such as overloaded constants and
1565character names) were not correctly set up.
1566
1567=item defined(@array) is deprecated
1568
1569(D) defined() is not usually useful on arrays because it checks for an
1570undefined I<scalar> value. If you want to see if the array is empty,
1571just use C<if (@array) { # not empty }> for example.
1572
1573=item defined(%hash) is deprecated
1574
1575(D) defined() is not usually useful on hashes because it checks for an
1576undefined I<scalar> value. If you want to see if the hash is empty,
1577just use C<if (%hash) { # not empty }> for example.
1578
1579=item Did not produce a valid header
1580
1581See Server error.
1582
1583=item Document contains no data
1584
1585See Server error.
1586
1587=item entering effective %s failed
1588
1589(F) While under the C<use filetest> pragma, switching the real and
1590effective uids or gids failed.
6b121555 1591
73b437c8
JH
1592=item false [] range "%s" in regexp
1593
1594(W) A character class range must start and end at a literal character, not
1595another character class like C<\d> or C<[:alpha:]>. The "-" in your false
1596range is interpreted as a literal "-". Consider quoting the "-", "\-".
1597See L<perlre>.
1598
af8c498a 1599=item Filehandle %s opened only for output
6b121555 1600
af8c498a 1601(W) You tried to read from a filehandle opened only for writing. If you
437784d6 1602intended it to be a read/write filehandle, you needed to open it with
af8c498a
GS
1603"+E<lt>" or "+E<gt>" or "+E<gt>E<gt>" instead of with "E<lt>" or nothing. If
1604you intended only to read from the file, use "E<lt>". See
1605L<perlfunc/open>.
e02fdbd2 1606
a99ba403
GS
1607=item Hexadecimal number > 0xffffffff non-portable
1608
1609(W) The hexadecimal number you specified is larger than 2**32-1
1610(4294967295) and therefore non-portable between systems. See
1611L<perlport> for more on portability concerns.
1612
1613=item Ill-formed CRTL environ value "%s"
1614
1615(W) A warning peculiar to VMS. Perl tried to read the CRTL's internal
1616environ array, and encountered an element without the C<=> delimiter
1617used to spearate keys from values. The element is ignored.
1618
1619=item Ill-formed message in prime_env_iter: |%s|
1620
1621(W) A warning peculiar to VMS. Perl tried to read a logical name
1622or CLI symbol definition when preparing to iterate over %ENV, and
1623didn't see the expected delimiter between key and value, so the
1624line was ignored.
1625
1626=item Illegal binary digit %s
1627
437784d6 1628(F) You used a digit other than 0 or 1 in a binary number.
a99ba403
GS
1629
1630=item Illegal binary digit %s ignored
1631
1632(W) You may have tried to use a digit other than 0 or 1 in a binary number.
1633Interpretation of the binary number stopped before the offending digit.
1634
1635=item Illegal number of bits in vec
1636
1637(F) The number of bits in vec() (the third argument) must be a power of
1638two from 1 to 32 (or 64, if your platform supports that).
1639
1640=item Integer overflow in %s number
1641
1642(W) The hexadecimal, octal or binary number you have specified either
c6edd1b7 1643as a literal or as an argument to hex() or oct() is too big for your
a99ba403
GS
1644architecture, and has been converted to a floating point number. On a
164532-bit architecture the largest hexadecimal, octal or binary number
1646representable without overflow is 0xFFFFFFFF, 037777777777, or
16470b11111111111111111111111111111111 respectively. Note that Perl
1648transparently promotes all numbers to a floating point representation
1649internally--subject to loss of precision errors in subsequent
1650operations.
1651
09bef843
SB
1652=item Invalid %s attribute: %s
1653
1654The indicated attribute for a subroutine or variable was not recognized
1655by Perl or by a user-supplied handler. See L<attributes>.
1656
1657=item Invalid %s attributes: %s
1658
1659The indicated attributes for a subroutine or variable were not recognized
1660by Perl or by a user-supplied handler. See L<attributes>.
1661
73b437c8
JH
1662=item invalid [] range "%s" in regexp
1663
1664The offending range is now explicitly displayed.
1665
09bef843
SB
1666=item Invalid separator character %s in attribute list
1667
1668(F) Something other than a comma or whitespace was seen between the
1669elements of an attribute list. If the previous attribute
1670had a parenthesised parameter list, perhaps that list was terminated
1671too soon. See L<attributes>.
1672
a99ba403
GS
1673=item Invalid separator character %s in subroutine attribute list
1674
1675(F) Something other than a comma or whitespace was seen between the
1676elements of a subroutine attribute list. If the previous attribute
1677had a parenthesised parameter list, perhaps that list was terminated
1678too soon.
1679
1680=item leaving effective %s failed
1681
1682(F) While under the C<use filetest> pragma, switching the real and
1683effective uids or gids failed.
1684
1685=item Lvalue subs returning %s not implemented yet
1686
1687(F) Due to limitations in the current implementation, array and hash
1688values cannot be returned in subroutines used in lvalue context.
1689See L<perlsub/"Lvalue subroutines">.
1690
1691=item Method %s not permitted
1692
1693See Server error.
1694
1695=item Missing %sbrace%s on \N{}
1696
1697(F) Wrong syntax of character name literal C<\N{charname}> within
1698double-quotish context.
1699
06eaf0bc
GS
1700=item Missing command in piped open
1701
1702(W) You used the C<open(FH, "| command")> or C<open(FH, "command |")>
1703construction, but the command was missing or blank.
1704
09bef843
SB
1705=item Missing name in "my sub"
1706
1707(F) The reserved syntax for lexically scoped subroutines requires that they
1708have a name with which they can be found.
1709
a99ba403
GS
1710=item no UTC offset information; assuming local time is UTC
1711
1712(S) A warning peculiar to VMS. Perl was unable to find the local
1713timezone offset, so it's assuming that local system time is equivalent
1714to UTC. If it's not, define the logical name F<SYS$TIMEZONE_DIFFERENTIAL>
1715to translate to the number of seconds which need to be added to UTC to
1716get local time.
1717
1718=item Octal number > 037777777777 non-portable
1719
1720(W) The octal number you specified is larger than 2**32-1 (4294967295)
1721and therefore non-portable between systems. See L<perlport> for more
1722on portability concerns.
1723
1724See also L<perlport> for writing portable code.
1725
1726=item panic: del_backref
1727
1728(P) Failed an internal consistency check while trying to reset a weak
1729reference.
1730
1731=item panic: kid popen errno read
1732
1733(F) forked child returned an incomprehensible message about its errno.
1734
1735=item panic: magic_killbackrefs
1736
1737(P) Failed an internal consistency check while trying to reset all weak
1738references to an object.
1739
1740=item Possible Y2K bug: %s
1741
1742(W) You are concatenating the number 19 with another number, which
1743could be a potential Year 2000 problem.
1744
1745=item Premature end of script headers
1746
1747See Server error.
1748
1749=item realloc() of freed memory ignored
1750
1751(S) An internal routine called realloc() on something that had already
1752been freed.
1753
1754=item Reference is already weak
1755
1756(W) You have attempted to weaken a reference that is already weak.
1757Doing so has no effect.
1758
1759=item setpgrp can't take arguments
1760
1761(F) Your system has the setpgrp() from BSD 4.2, which takes no arguments,
1762unlike POSIX setpgid(), which takes a process ID and process group ID.
1763
1764=item Strange *+?{} on zero-length expression
1765
1766(W) You applied a regular expression quantifier in a place where it
1767makes no sense, such as on a zero-width assertion.
1768Try putting the quantifier inside the assertion instead. For example,
1769the way to match "abc" provided that it is followed by three
1770repetitions of "xyz" is C</abc(?=(?:xyz){3})/>, not C</abc(?=xyz){3}/>.
1771
1772=item switching effective %s is not implemented
1773
1774(F) While under the C<use filetest> pragma, we cannot switch the
1775real and effective uids or gids.
1776
437784d6 1777=item This Perl can't reset CRTL environ elements (%s)
a99ba403
GS
1778
1779=item This Perl can't set CRTL environ elements (%s=%s)
1780
1781(W) Warnings peculiar to VMS. You tried to change or delete an element
1782of the CRTL's internal environ array, but your copy of Perl wasn't
1783built with a CRTL that contained the setenv() function. You'll need to
1784rebuild Perl with a CRTL that does, or redefine F<PERL_ENV_TABLES> (see
1785L<perlvms>) so that the environ array isn't the target of the change to
1786%ENV which produced the warning.
1787
1788=item Unknown open() mode '%s'
1789
437784d6
GS
1790(F) The second argument of 3-argument open() is not among the list
1791of valid modes: C<L<lt>>, C<L<gt>>, C<E<gt>E<gt>>, C<+L<lt>>,
1792C<+L<gt>>, C<+E<gt>E<gt>>, C<-|>, C<|->.
a99ba403
GS
1793
1794=item Unknown process %x sent message to prime_env_iter: %s
1795
1796(P) An error peculiar to VMS. Perl was reading values for %ENV before
1797iterating over it, and someone else stuck a message in the stream of
1798data Perl expected. Someone's very confused, or perhaps trying to
1799subvert Perl's population of %ENV for nefarious purposes.
1800
af8c498a
GS
1801=item Unrecognized escape \\%c passed through
1802
1803(W) You used a backslash-character combination which is not recognized
1028017a 1804by Perl. The character was understood literally.
af8c498a 1805
09bef843
SB
1806=item Unterminated attribute parameter in attribute list
1807
1808(F) The lexer saw an opening (left) parenthesis character while parsing an
1809attribute list, but the matching closing (right) parenthesis
1810character was not found. You may need to add (or remove) a backslash
1811character to get your parentheses to balance. See L<attributes>.
1812
1813=item Unterminated attribute list
1814
1815(F) The lexer found something other than a simple identifier at the start
1816of an attribute, and it wasn't a semicolon or the start of a
1817block. Perhaps you terminated the parameter list of the previous attribute
1818too soon. See L<attributes>.
1819
09bef843
SB
1820=item Unterminated attribute parameter in subroutine attribute list
1821
1822(F) The lexer saw an opening (left) parenthesis character while parsing a
1823subroutine attribute list, but the matching closing (right) parenthesis
1824character was not found. You may need to add (or remove) a backslash
1825character to get your parentheses to balance.
1826
1827=item Unterminated subroutine attribute list
1828
1829(F) The lexer found something other than a simple identifier at the start
1830of a subroutine attribute, and it wasn't a semicolon or the start of a
1831block. Perhaps you terminated the parameter list of the previous attribute
1832too soon.
1833
a99ba403 1834=item Value of CLI symbol "%s" too long
eb6e2d6f 1835
a99ba403
GS
1836(W) A warning peculiar to VMS. Perl tried to read the value of an %ENV
1837element from a CLI symbol table, and found a resultant string longer
1838than 1024 characters. The return value has been truncated to 1024
1839characters.
eb6e2d6f 1840
a99ba403 1841=item Version number must be a constant number
ba8251e8 1842
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1843(P) The attempt to translate a C<use Module n.n LIST> statement into
1844its equivalent C<BEGIN> block found an internal inconsistency with
1845the version number.
1846
1847=back
27806c82 1848
a5222a85 1849=head1 Obsolete Diagnostics
3175b8cd 1850
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1851=over 4
1852
1853=item Character class syntax [: :] is reserved for future extensions
1854
1855(W) Within regular expression character classes ([]) the syntax beginning
1856with "[:" and ending with ":]" is reserved for future extensions.
1857If you need to represent those character sequences inside a regular
1858expression character class, just quote the square brackets with the
1859backslash: "\[:" and ":\]".
1860
1861=item Ill-formed logical name |%s| in prime_env_iter
1862
1863(W) A warning peculiar to VMS. A logical name was encountered when preparing
1864to iterate over %ENV which violates the syntactic rules governing logical
1865names. Because it cannot be translated normally, it is skipped, and will not
1866appear in %ENV. This may be a benign occurrence, as some software packages
1867might directly modify logical name tables and introduce nonstandard names,
1868or it may indicate that a logical name table has been corrupted.
1869
1870=item regexp too big
1871
1872(F) The current implementation of regular expressions uses shorts as
1873address offsets within a string. Unfortunately this means that if
1874the regular expression compiles to longer than 32767, it'll blow up.
1875Usually when you want a regular expression this big, there is a better
1876way to do it with multiple statements. See L<perlre>.
1877
1878=item Use of "$$<digit>" to mean "${$}<digit>" is deprecated
1879
1880(D) Perl versions before 5.004 misinterpreted any type marker followed
1881by "$" and a digit. For example, "$$0" was incorrectly taken to mean
1882"${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004.
1883
1884However, the developers of Perl 5.004 could not fix this bug completely,
1885because at least two widely-used modules depend on the old meaning of
1886"$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the
1887old (broken) way inside strings; but it generates this message as a
1888warning. And in Perl 5.005, this special treatment will cease.
1889
1890=back
3175b8cd 1891
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1892=head1 BUGS
1893
437784d6 1894If you find what you think is a bug, you might check the
14218588 1895articles recently posted to the comp.lang.perl.misc newsgroup.
ba8251e8
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1896There may also be information at http://www.perl.com/perl/, the Perl
1897Home Page.
1898
1899If you believe you have an unreported bug, please run the B<perlbug>
14218588 1900program included with your release. Make sure to trim your bug down
ba8251e8 1901to a tiny but sufficient test case. Your bug report, along with the
14218588 1902output of C<perl -V>, will be sent off to perlbug@perl.com to be
ba8251e8
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1903analysed by the Perl porting team.
1904
1905=head1 SEE ALSO
1906
1907The F<Changes> file for exhaustive details on what changed.
1908
1909The F<INSTALL> file for how to build Perl.
1910
1911The F<README> file for general stuff.
1912
1913The F<Artistic> and F<Copying> files for copyright information.
1914
1915=head1 HISTORY
1916
a5222a85
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1917Written by Gurusamy Sarathy <F<gsar@activestate.com>>, with many
1918contributions from The Perl Porters.
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1919
1920Send omissions or corrections to <F<perlbug@perl.com>>.
1921
1922=cut