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1 | =head1 NAME |
2 | |
3 | perlnews - what's new for perl5.004 |
4 | |
5 | =head1 DESCRIPTION |
6 | |
7 | This document describes differences between the 5.003 release (as |
8 | documented in I<Programming Perl>, second edition--the Camel Book) and |
9 | this one. |
10 | |
11 | =head1 Supported Environments |
12 | |
13 | Perl5.004 builds out of the box on Unix, Plan9, LynxOS, VMS, OS/2, |
14 | QNX, and AmigaOS. |
15 | |
16 | =head1 Core Changes |
17 | |
18 | Most importantly, many bugs were fixed. See the F<Changes> |
19 | file in the distribution for details. |
20 | |
21 | =head2 Compilation Option: Binary Compatibility With 5.003 |
22 | |
23 | There is a new Configure question that asks if you want to maintain |
24 | binary compatibility with Perl 5.003. If you choose binary |
25 | compatibility, you do not have to recompile your extensions, but you |
26 | might have symbol conflicts if you embed Perl in another application. |
27 | |
28 | =head2 Internal Change: FileHandle Deprecated |
29 | |
30 | Filehandles are now stored internally as type IO::Handle. |
31 | Although C<use FileHandle> and C<*STDOUT{FILEHANDLE}> |
32 | are still supported for backwards compatibility |
33 | C<use IO::Handle> (or C<IO::Seekable> or C<IO::File>) and |
34 | C<*STDOUT{IO}> are the way of the future. |
35 | |
36 | =head2 Internal Change: Safe Module Absorbed into Opcode |
37 | |
38 | A new Opcode module subsumes 5.003's Safe module. The Safe |
39 | interface is still available, so existing scripts should still |
40 | work, but users are encouraged to read the new Opcode documentation. |
41 | |
42 | =head2 Internal Change: PerlIO internal IO abstraction interface. |
43 | |
44 | It is now possible to build Perl with AT&T's sfio IO package |
45 | instead of stdio. See L<perlapio> for more details, and |
46 | the F<INSTALL> file for how to use it. |
47 | |
48 | =head2 New and Changed Built-in Variables |
49 | |
50 | =over |
51 | |
52 | =item $^E |
53 | |
54 | Extended error message under some platforms ($EXTENDED_OS_ERROR |
55 | if you C<use English>). |
56 | |
57 | =item $^H |
58 | |
59 | The current set of syntax checks enabled by C<use strict>. See the |
60 | documentation of C<strict> for more details. Not actually new, but |
61 | newly documented. |
62 | Because it is intended for internal use by Perl core components, |
63 | there is no C<use English> long name for this variable. |
64 | |
65 | =item $^M |
66 | |
67 | By default, running out of memory it is not trappable. However, if |
68 | compiled for this, Perl may use the contents of C<$^M> as an emergency |
69 | pool after die()ing with this message. Suppose that your Perl were |
70 | compiled with -DEMERGENCY_SBRK and used Perl's malloc. Then |
71 | |
72 | $^M = 'a' x (1<<16); |
73 | |
74 | would allocate 64K buffer for use when in emergency. |
75 | See the F<INSTALL> file for information on how to enable this option. |
76 | As a disincentive to casual use of this advanced feature, |
77 | there is no C<use English> long name for this variable. |
78 | |
79 | =back |
80 | |
81 | =head2 New and Changed Built-in Functions |
82 | |
83 | =over |
84 | |
85 | =item delete on slices |
86 | |
87 | This now works. (e.g. C<delete @ENV{'PATH', 'MANPATH'}>) |
88 | |
89 | =item flock |
90 | |
91 | is now supported on more platforms, and prefers fcntl |
92 | to lockf when emulating. |
93 | |
94 | =item keys as an lvalue |
95 | |
96 | As an lvalue, C<keys> allows you to increase the number of hash buckets |
97 | allocated for the given associative array. This can gain you a measure |
98 | of efficiency if you know the hash is going to get big. (This is |
99 | similar to pre-extending an array by assigning a larger number to |
100 | $#array.) If you say |
101 | |
102 | keys %hash = 200; |
103 | |
104 | then C<%hash> will have at least 200 buckets allocated for it. These |
105 | buckets will be retained even if you do C<%hash = ()>; use C<undef |
106 | %hash> if you want to free the storage while C<%hash> is still in scope. |
107 | You can't shrink the number of buckets allocated for the hash using |
108 | C<keys> in this way (but you needn't worry about doing this by accident, |
109 | as trying has no effect). |
110 | |
111 | =item my() in Control Structures |
112 | |
113 | You can now use my() (with or without the parentheses) in the control |
114 | expressions of control structures such as: |
115 | |
116 | while (my $line = <>) { |
117 | $line = lc $line; |
118 | } continue { |
119 | print $line; |
120 | } |
121 | |
122 | if ((my $answer = <STDIN>) =~ /^yes$/i) { |
123 | user_agrees(); |
124 | } elsif ($answer =~ /^no$/i) { |
125 | user_disagrees(); |
126 | } else { |
127 | chomp $answer; |
128 | die "'$answer' is neither 'yes' nor 'no'"; |
129 | } |
130 | |
131 | Also, you can declare a foreach loop control variable as lexical by |
132 | preceding it with the word "my". For example, in: |
133 | |
134 | foreach my $i (1, 2, 3) { |
135 | some_function(); |
136 | } |
137 | |
138 | $i is a lexical variable, and the scope of $i extends to the end of |
139 | the loop, but not beyond it. |
140 | |
141 | Note that you still cannot use my() on global punctuation variables |
142 | such as $_ and the like. |
143 | |
144 | =item unpack() and pack() |
145 | |
146 | A new format 'w' represents a BER compressed integer (as defined in |
147 | ASN.1). Its format is a sequence of one or more bytes, each of which |
148 | provides seven bits of the total value, with the most significant |
149 | first. Bit eight of each byte is set, except for the last byte, in |
150 | which bit eight is clear. |
151 | |
152 | =item use VERSION |
153 | |
154 | If the first argument to C<use> is a number, it is treated as a version |
155 | number instead of a module name. If the version of the Perl interpreter |
156 | is less than VERSION, then an error message is printed and Perl exits |
157 | immediately. This is often useful if you need to check the current |
158 | Perl version before C<use>ing library modules which have changed in |
159 | incompatible ways from older versions of Perl. (We try not to do |
160 | this more than we have to.) |
161 | |
162 | =item use Module VERSION LIST |
163 | |
164 | If the VERSION argument is present between Module and LIST, then the |
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165 | C<use> will call the VERSION method in class Module with the given |
166 | version as an argument. The default VERSION method, inherited from |
167 | the Universal class, croaks if the given version is larger than the |
168 | value of the variable $Module::VERSION. (Note that there is not a |
169 | comma after VERSION!) |
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170 | |
171 | =item prototype(FUNCTION) |
172 | |
173 | Returns the prototype of a function as a string (or C<undef> if the |
174 | function has no prototype). FUNCTION is a reference to or the name of the |
175 | function whose prototype you want to retrieve. |
176 | (Not actually new; just never documented before.) |
177 | |
178 | =item $_ as Default |
179 | |
180 | Functions documented in the Camel to default to $_ now in |
181 | fact do, and all those that do are so documented in L<perlfunc>. |
182 | |
183 | =back |
184 | |
185 | =head2 New Built-in Methods |
186 | |
187 | The C<UNIVERSAL> package automatically contains the following methods that |
188 | are inherited by all other classes: |
189 | |
190 | =over 4 |
191 | |
192 | =item isa(CLASS) |
193 | |
194 | C<isa> returns I<true> if its object is blessed into a sub-class of C<CLASS> |
195 | |
196 | C<isa> is also exportable and can be called as a sub with two arguments. This |
197 | allows the ability to check what a reference points to. Example: |
198 | |
199 | use UNIVERSAL qw(isa); |
200 | |
201 | if(isa($ref, 'ARRAY')) { |
202 | ... |
203 | } |
204 | |
205 | =item can(METHOD) |
206 | |
207 | C<can> checks to see if its object has a method called C<METHOD>, |
208 | if it does then a reference to the sub is returned; if it does not then |
209 | I<undef> is returned. |
210 | |
211 | =item VERSION( [NEED] ) |
212 | |
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213 | C<VERSION> returns the version number of the class (package). If the |
214 | NEED argument is given then it will check that the current version (as |
215 | defined by the $VERSION variable in the given package) not less than |
216 | NEED; it will die if this is not the case. This method is normally |
217 | called as a class method. This method is called automatically by the |
218 | C<VERSION> form of C<use>. |
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219 | |
220 | use A 1.2 qw(some imported subs); |
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221 | # implies: |
222 | A->VERSION(1.2); |
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223 | |
224 | =item class() |
225 | |
226 | C<class> returns the class name of its object. |
227 | |
228 | =item is_instance() |
229 | |
230 | C<is_instance> returns true if its object is an instance of some |
231 | class, false if its object is the class (package) itself. Example |
232 | |
233 | A->is_instance(); # False |
234 | |
235 | $var = 'A'; |
236 | $var->is_instance(); # False |
237 | |
238 | $ref = bless [], 'A'; |
239 | $ref->is_instance(); # True |
240 | |
241 | =back |
242 | |
243 | B<NOTE:> C<can> directly uses Perl's internal code for method lookup, and |
244 | C<isa> uses a very similar method and cache-ing strategy. This may cause |
245 | strange effects if the Perl code dynamically changes @ISA in any package. |
246 | |
247 | You may add other methods to the UNIVERSAL class via Perl or XS code. |
248 | You do not need to C<use UNIVERSAL> in order to make these methods |
249 | available to your program. This is necessary only if you wish to |
250 | have C<isa> available as a plain subroutine in the current package. |
251 | |
252 | =head2 TIEHANDLE Now Supported |
253 | |
254 | =over |
255 | |
256 | =item TIEHANDLE classname, LIST |
257 | |
258 | This is the constructor for the class. That means it is expected to |
259 | return an object of some sort. The reference can be used to |
260 | hold some internal information. |
261 | |
262 | sub TIEHANDLE { print "<shout>\n"; my $i; bless \$i, shift } |
263 | |
264 | =item PRINT this, LIST |
265 | |
266 | This method will be triggered every time the tied handle is printed to. |
267 | Beyond its self reference it also expects the list that was passed to |
268 | the print function. |
269 | |
270 | sub PRINT { $r = shift; $$r++; print join($,,map(uc($_),@_)),$\ } |
271 | |
272 | =item READLINE this |
273 | |
274 | This method will be called when the handle is read from. The method |
275 | should return undef when there is no more data. |
276 | |
277 | sub READLINE { $r = shift; "PRINT called $$r times\n"; } |
278 | |
279 | =item DESTROY this |
280 | |
281 | As with the other types of ties, this method will be called when the |
282 | tied handle is about to be destroyed. This is useful for debugging and |
283 | possibly for cleaning up. |
284 | |
285 | sub DESTROY { print "</shout>\n" } |
286 | |
287 | =back |
288 | |
289 | =head1 Pragmata |
290 | |
291 | Three new pragmatic modules exist: |
292 | |
293 | =over |
294 | |
295 | =item use blib |
296 | |
297 | Looks for MakeMaker-like I<'blib'> directory structure starting in |
298 | I<dir> (or current directory) and working back up to five levels of |
299 | parent directories. |
300 | |
301 | Intended for use on command line with B<-M> option as a way of testing |
302 | arbitrary scripts against an uninstalled version of a package. |
303 | |
304 | =item use locale |
305 | |
306 | Tells the compiler to enable (or disable) the use of POSIX locales for |
307 | built-in operations. |
308 | |
309 | When C<use locale> is in effect, the current LC_CTYPE locale is used |
310 | for regular expressions and case mapping; LC_COLLATE for string |
311 | ordering; and LC_NUMERIC for numeric formating in printf and sprintf |
312 | (but B<not> in print). LC_NUMERIC is always used in write, since |
313 | lexical scoping of formats is problematic at best. |
314 | |
315 | Each C<use locale> or C<no locale> affects statements to the end of |
316 | the enclosing BLOCK or, if not inside a BLOCK, to the end of the |
317 | current file. Locales can be switched and queried with |
318 | POSIX::setlocale(). |
319 | |
320 | See L<perllocale> for more information. |
321 | |
322 | =item use ops |
323 | |
324 | Restricts unsafe operations when compiling. |
325 | |
326 | =back |
327 | |
328 | =head1 Modules |
329 | |
330 | =head2 Module Information Summary |
331 | |
332 | Brand new modules: |
333 | |
334 | IO.pm Top-level interface to IO::* classes |
335 | IO/File.pm IO::File extension Perl module |
336 | IO/Handle.pm IO::Handle extension Perl module |
337 | IO/Pipe.pm IO::Pipe extension Perl module |
338 | IO/Seekable.pm IO::Seekable extension Perl module |
339 | IO/Select.pm IO::Select extension Perl module |
340 | IO/Socket.pm IO::Socket extension Perl module |
341 | |
342 | Opcode.pm Disable named opcodes when compiling Perl code |
343 | |
344 | ExtUtils/Embed.pm Utilities for embedding Perl in C programs |
345 | ExtUtils/testlib.pm Fixes up @INC to use just-built extension |
346 | |
347 | Fatal.pm Make do-or-die equivalents of functions |
348 | FindBin.pm Find path of currently executing program |
349 | |
350 | Class/Template.pm Structure/member template builder |
351 | File/stat.pm Object-oriented wrapper around CORE::stat |
352 | Net/hostent.pm Object-oriented wrapper around CORE::gethost* |
353 | Net/netent.pm Object-oriented wrapper around CORE::getnet* |
354 | Net/protoent.pm Object-oriented wrapper around CORE::getproto* |
355 | Net/servent.pm Object-oriented wrapper around CORE::getserv* |
356 | Time/gmtime.pm Object-oriented wrapper around CORE::gmtime |
357 | Time/localtime.pm Object-oriented wrapper around CORE::localtime |
358 | Time/tm.pm Perl implementation of "struct tm" for {gm,local}time |
359 | User/grent.pm Object-oriented wrapper around CORE::getgr* |
360 | User/pwent.pm Object-oriented wrapper around CORE::getpw* |
361 | |
362 | UNIVERSAL.pm Base class for *ALL* classes |
363 | |
364 | =head2 IO |
365 | |
366 | The IO module provides a simple mechanism to load all of the IO modules at one |
367 | go. Currently this includes: |
368 | |
369 | IO::Handle |
370 | IO::Seekable |
371 | IO::File |
372 | IO::Pipe |
373 | IO::Socket |
374 | |
375 | For more information on any of these modules, please see its |
376 | respective documentation. |
377 | |
378 | =head2 Math::Complex |
379 | |
380 | The Math::Complex module has been totally rewritten, and now supports |
381 | more operations. These are overloaded: |
382 | |
383 | + - * / ** <=> neg ~ abs sqrt exp log sin cos atan2 "" (stringify) |
384 | |
385 | And these functions are now exported: |
386 | |
387 | pi i Re Im arg |
388 | log10 logn cbrt root |
389 | tan cotan asin acos atan acotan |
390 | sinh cosh tanh cotanh asinh acosh atanh acotanh |
391 | cplx cplxe |
392 | |
393 | =head2 Overridden Built-ins |
394 | |
395 | Many of the Perl built-ins returning lists now have |
396 | object-oriented overrides. These are: |
397 | |
398 | File::stat |
399 | Net::hostent |
400 | Net::netent |
401 | Net::protoent |
402 | Net::servent |
403 | Time::gmtime |
404 | Time::localtime |
405 | User::grent |
406 | User::pwent |
407 | |
408 | For example, you can now say |
409 | |
410 | use File::stat; |
411 | use User::pwent; |
412 | $his = (stat($filename)->st_uid == pwent($whoever)->pw_uid); |
413 | |
414 | =head1 Efficiency Enhancements |
415 | |
416 | All hash keys with the same string are only allocated once, so |
417 | even if you have 100 copies of the same hash, the immutable keys |
418 | never have to be re-allocated. |
419 | |
420 | Functions that do nothing but return a fixed value are now inlined. |
421 | |
422 | =head1 Documentation Changes |
423 | |
424 | Many of the base and library pods were updated. These |
425 | new pods are included in section 1: |
426 | |
427 | =over 4 |
428 | |
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429 | =item L<perlnews> |
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430 | |
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431 | This document. |
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432 | |
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433 | =item L<perllocale> |
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434 | |
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435 | Locale support (internationalization and localization). |
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436 | |
437 | =item L<perltoot> |
438 | |
439 | Tutorial on Perl OO programming. |
440 | |
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441 | =item L<perlapio> |
442 | |
443 | Perl internal IO abstraction interface. |
444 | |
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445 | =item L<perldebug> |
446 | |
447 | Although not new, this has been massively updated. |
448 | |
449 | =item L<perlsec> |
450 | |
451 | Although not new, this has been massively updated. |
452 | |
453 | =back |
454 | |
455 | =head1 New Diagnostics |
456 | |
457 | Several new conditions will trigger warnings that were |
458 | silent before. Some only affect certain platforms. |
459 | The following new warnings and errors |
460 | outline these: |
461 | |
462 | =over 4 |
463 | |
464 | =item "my" variable %s masks earlier declaration in same scope |
465 | |
466 | (S) A lexical variable has been redeclared in the same scope, effectively |
467 | eliminating all access to the previous instance. This is almost always |
468 | a typographical error. Note that the earlier variable will still exist |
469 | until the end of the scope or until all closure referents to it are |
470 | destroyed. |
471 | |
472 | =item Allocation too large: %lx |
473 | |
474 | (X) You can't allocate more than 64K on an MSDOS machine. |
475 | |
476 | =item Allocation too large |
477 | |
478 | (F) You can't allocate more than 2^31+"small amount" bytes. |
479 | |
480 | =item Attempt to free non-existent shared string |
481 | |
482 | (P) Perl maintains a reference counted internal table of strings to |
483 | optimize the storage and access of hash keys and other strings. This |
484 | indicates someone tried to decrement the reference count of a string |
485 | that can no longer be found in the table. |
486 | |
487 | =item Attempt to use reference as lvalue in substr |
488 | |
489 | (W) You supplied a reference as the first argument to substr() used |
490 | as an lvalue, which is pretty strange. Perhaps you forgot to |
491 | dereference it first. See L<perlfunc/substr>. |
492 | |
493 | =item Unsupported function fork |
494 | |
495 | (F) Your version of executable does not support forking. |
496 | |
497 | Note that under some systems, like OS/2, there may be different flavors of |
498 | Perl executables, some of which may support fork, some not. Try changing |
499 | the name you call Perl by to C<perl_>, C<perl__>, and so on. |
500 | |
501 | =item Ill-formed logical name |%s| in prime_env_iter |
502 | |
503 | (W) A warning peculiar to VMS. A logical name was encountered when preparing |
504 | to iterate over %ENV which violates the syntactic rules governing logical |
505 | names. Since it cannot be translated normally, it is skipped, and will not |
506 | appear in %ENV. This may be a benign occurrence, as some software packages |
507 | might directly modify logical name tables and introduce non-standard names, |
508 | or it may indicate that a logical name table has been corrupted. |
509 | |
510 | =item Integer overflow in hex number |
511 | |
512 | (S) The literal hex number you have specified is too big for your |
513 | architecture. On a 32-bit architecture the largest hex literal is |
514 | 0xFFFFFFFF. |
515 | |
516 | =item Integer overflow in octal number |
517 | |
518 | (S) The literal octal number you have specified is too big for your |
519 | architecture. On a 32-bit architecture the largest octal literal is |
520 | 037777777777. |
521 | |
522 | =item Null picture in formline |
523 | |
524 | (F) The first argument to formline must be a valid format picture |
525 | specification. It was found to be empty, which probably means you |
526 | supplied it an uninitialized value. See L<perlform>. |
527 | |
528 | =item Offset outside string |
529 | |
530 | (F) You tried to do a read/write/send/recv operation with an offset |
531 | pointing outside the buffer. This is difficult to imagine. |
532 | The sole exception to this is that C<sysread()>ing past the buffer |
533 | will extend the buffer and zero pad the new area. |
534 | |
535 | =item Out of memory! |
536 | |
537 | (X|F) The malloc() function returned 0, indicating there was insufficient |
538 | remaining memory (or virtual memory) to satisfy the request. |
539 | |
540 | The request was judged to be small, so the possibility to trap it |
541 | depends on the way Perl was compiled. By default it is not trappable. |
542 | However, if compiled for this, Perl may use the contents of C<$^M> as |
543 | an emergency pool after die()ing with this message. In this case the |
544 | error is trappable I<once>. |
545 | |
546 | =item Out of memory during request for %s |
547 | |
548 | (F) The malloc() function returned 0, indicating there was insufficient |
549 | remaining memory (or virtual memory) to satisfy the request. However, |
550 | the request was judged large enough (compile-time default is 64K), so |
551 | a possibility to shut down by trapping this error is granted. |
552 | |
553 | =item Possible attempt to put comments in qw() list |
554 | |
555 | (W) You probably wrote something like this: |
556 | |
557 | qw( a # a comment |
558 | b # another comment |
559 | ) ; |
560 | |
561 | when you should have written this: |
562 | |
563 | qw( a |
564 | b |
565 | ) ; |
566 | |
567 | =item Possible attempt to separate words with commas |
568 | |
569 | (W) You probably wrote something like this: |
570 | |
571 | qw( a, b, c ); |
572 | |
573 | when you should have written this: |
574 | |
575 | qw( a b c ); |
576 | |
577 | =item untie attempted while %d inner references still exist |
578 | |
579 | (W) A copy of the object returned from C<tie> (or C<tied>) was still |
580 | valid when C<untie> was called. |
581 | |
582 | =item Got an error from DosAllocMem: |
583 | |
584 | (P) An error peculiar to OS/2. Most probably you use an obsolete version |
585 | of Perl, and should not happen anyway. |
586 | |
587 | =item Malformed PERLLIB_PREFIX |
588 | |
589 | (F) An error peculiar to OS/2. PERLLIB_PREFIX should be of the form |
590 | |
591 | prefix1;prefix2 |
592 | |
593 | or |
594 | |
595 | prefix1 prefix2 |
596 | |
597 | with non-empty prefix1 and prefix2. If C<prefix1> is indeed a prefix of |
598 | a builtin library search path, prefix2 is substituted. The error may appear |
599 | if components are not found, or are too long. See L<perlos2/"PERLLIB_PREFIX">. |
600 | |
601 | =item PERL_SH_DIR too long |
602 | |
603 | (F) An error peculiar to OS/2. PERL_SH_DIR is the directory to find the |
604 | C<sh>-shell in. See L<perlos2/"PERL_SH_DIR">. |
605 | |
606 | =item Process terminated by SIG%s |
607 | |
608 | (W) This is a standard message issued by OS/2 applications, while *nix |
609 | applications die in silence. It is considered a feature of the OS/2 |
610 | port. One can easily disable this by appropriate sighandlers, see |
611 | L<perlipc/"Signals">. See L<perlos2/"Process terminated by SIGTERM/SIGINT">. |
612 | |
613 | =back |
614 | |
615 | =head1 BUGS |
616 | |
617 | If you find what you think is a bug, you might check the headers |
618 | of recently posted articles |
619 | in the comp.lang.perl.misc newsgroup. There may also be |
620 | information at http://www.perl.com/perl/, the Perl Home Page. |
621 | |
622 | If you believe you have an unreported bug, please run the B<perlbug> |
623 | program included with your release. Make sure you trim your bug |
624 | down to a tiny but sufficient test case. Your bug report, along |
625 | with the output of C<perl -V>, will be sent off to perlbug@perl.com |
626 | to be analysed by the Perl porting team. |
627 | |
628 | =head1 SEE ALSO |
629 | |
630 | The F<Changes> file for exhaustive details on what changed. |
631 | |
632 | The F<INSTALL> file for how to build Perl. This file has been |
633 | significantly updated for 5.004, so even veteran users should |
634 | look through it. |
635 | |
636 | The F<README> file for general stuff. |
637 | |
638 | The F<Copying> file for copyright information. |
639 | |
640 | =head1 HISTORY |
641 | |
642 | Constructed by Tom Christiansen, grabbing material with permission |
643 | from innumerable contributors, with kibitzing by more than a few Perl |
644 | porters. |
645 | |
646 | Last update: |
647 | Wed Dec 18 16:18:27 EST 1996 |