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1 | =head1 NAME |
2 | |
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3 | perldelta - what's new for perl5.004 |
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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, |
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14 | QNX, AmigaOS, and Windows NT; once built on Windows NT, Perl runs |
15 | on Windows 95 as well. |
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16 | |
17 | =head1 Core Changes |
18 | |
19 | Most importantly, many bugs were fixed. See the F<Changes> |
20 | file in the distribution for details. |
21 | |
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22 | =head2 Compilation option: Binary compatibility with 5.003 |
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23 | |
24 | There is a new Configure question that asks if you want to maintain |
25 | binary compatibility with Perl 5.003. If you choose binary |
26 | compatibility, you do not have to recompile your extensions, but you |
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27 | might have symbol conflicts if you embed Perl in another application, |
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28 | just as in the 5.003 release. By default, binary compatibility |
29 | is preserved at the expense of symbol table pollution. |
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30 | |
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31 | =head2 $PERL5OPT environment variable |
32 | |
33 | You may now put Perl options in the $PERL5OPT environment variable. |
34 | Unless Perl is running with taint checks, it will interpret this |
35 | variable as if its contents had appeared on a "#!perl" line at the |
36 | beginning of your script, except that hyphens are optional. PERL5OPT |
37 | may only be used to set the following switches: B<-[DIMUdmw]>. |
38 | |
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39 | =head2 Limitations on B<-M>, and C<-m>, and B<-T> options |
40 | |
41 | The C<-M> and C<-m> options are no longer allowed on the C<#!> line of |
42 | a script. If a script needs a module, it should invoke it with the |
43 | C<use> pragma. |
44 | |
45 | The B<-T> option is also forbidden on the C<#!> line of a script, |
46 | unless it was present on the Perl command line. Due to the way C<#!> |
47 | works, this usually means that B<-T> must be in the first argument. |
48 | Thus: |
49 | |
50 | #!/usr/bin/perl -T -w |
51 | |
52 | will probably work for an executable script invoked as C<scriptname>, |
53 | while: |
54 | |
55 | #!/usr/bin/perl -w -T |
56 | |
57 | will probably fail under the same conditions. (Non-Unix systems will |
58 | probably not follow this rule.) But C<perl scriptname> is guaranteed |
59 | to fail, since then there is no chance of B<-T> being found on the |
60 | command line before it is found on the C<#!> line. |
61 | |
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62 | =head2 More precise warnings |
63 | |
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64 | If you removed the B<-w> option from your Perl 5.003 scripts because it |
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65 | made Perl too verbose, we recommend that you try putting it back when |
66 | you upgrade to Perl 5.004. Each new perl version tends to remove some |
67 | undesirable warnings, while adding new warnings that may catch bugs in |
68 | your scripts. |
69 | |
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70 | =head2 Deprecated: Inherited C<AUTOLOAD> for non-methods |
71 | |
72 | Before Perl 5.004, C<AUTOLOAD> functions were looked up as methods |
73 | (using the C<@ISA> hierarchy), even when the function to be autoloaded |
74 | was called as a plain function (e.g. C<Foo::bar()>), not a method |
75 | (e.g. C<Foo->bar()> or C<$obj->bar()>). |
76 | |
77 | Perl 5.005 will use method lookup only for methods' C<AUTOLOAD>s. |
78 | However, there is a significant base of existing code that may be using |
79 | the old behavior. So, as an interim step, Perl 5.004 issues an optional |
80 | warning when a non-method uses an inherited C<AUTOLOAD>. |
81 | |
82 | The simple rule is: Inheritance will not work when autoloading |
83 | non-methods. The simple fix for old code is: In any module that used to |
84 | depend on inheriting C<AUTOLOAD> for non-methods from a base class named |
85 | C<BaseClass>, execute C<*AUTOLOAD = \&BaseClass::AUTOLOAD> during startup. |
86 | |
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87 | =head2 Subroutine arguments created only when they're modified |
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88 | |
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89 | In Perl 5.004, nonexistent array and hash elements used as subroutine |
90 | parameters are brought into existence only if they are actually |
91 | assigned to (via C<@_>). |
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92 | |
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93 | Earlier versions of Perl vary in their handling of such arguments. |
94 | Perl versions 5.002 and 5.003 always brought them into existence. |
95 | Perl versions 5.000, 5.001, and 5.002 brought them into existence only |
96 | if they were not the first argument (which was almost certainly a |
97 | bug). Earlier versions of Perl never brought them into existence. |
98 | |
99 | For example, given this code: |
100 | |
101 | undef @a; undef %a; |
102 | sub show { print $_[0] }; |
103 | sub change { $_[0]++ }; |
104 | show($a[2]); |
105 | change($a{b}); |
106 | |
107 | After this code executes in Perl 5.004, $a{b} exists but $a[2] does |
108 | not. In Perl 5.002 and 5.003, both $a{b} and $a[2] would have existed |
109 | (but $a[2]'s value would have been undefined). |
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110 | |
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111 | =head2 Group vector changeable with C<$)> |
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112 | |
113 | The C<$)> special variable has always (well, in Perl 5, at least) |
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114 | reflected not only the current effective group, but also the group list |
115 | as returned by the C<getgroups()> C function (if there is one). |
116 | However, until this release, there has not been a way to call the |
117 | C<setgroups()> C function from Perl. |
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118 | |
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119 | In Perl 5.004, assigning to C<$)> is exactly symmetrical with examining |
120 | it: The first number in its string value is used as the effective gid; |
121 | if there are any numbers after the first one, they are passed to the |
122 | C<setgroups()> C function (if there is one). |
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123 | |
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124 | =head2 Fixed parsing of $$<digit>, &$<digit>, etc. |
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125 | |
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126 | Perl versions before 5.004 misinterpreted any type marker followed by |
127 | "$" and a digit. For example, "$$0" was incorrectly taken to mean |
128 | "${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004. |
129 | |
130 | However, the developers of Perl 5.004 could not fix this bug completely, |
131 | because at least two widely-used modules depend on the old meaning of |
132 | "$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the |
133 | old (broken) way inside strings; but it generates this message as a |
134 | warning. And in Perl 5.005, this special treatment will cease. |
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135 | |
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136 | =head2 No resetting of $. on implicit close |
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137 | |
138 | The documentation for Perl 5.0 has always stated that C<$.> is I<not> |
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139 | reset when an already-open file handle is reopened with no intervening |
140 | call to C<close>. Due to a bug, perl versions 5.000 through 5.003 |
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141 | I<did> reset C<$.> under that circumstance; Perl 5.004 does not. |
142 | |
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143 | =head2 C<wantarray> may return undef |
144 | |
145 | The C<wantarray> operator returns true if a subroutine is expected to |
146 | return a list, and false otherwise. In Perl 5.004, C<wantarray> can |
147 | also return the undefined value if a subroutine's return value will |
148 | not be used at all, which allows subroutines to avoid a time-consuming |
149 | calculation of a return value if it isn't going to be used. |
150 | |
151 | =head2 Changes to tainting checks |
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152 | |
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153 | A bug in previous versions may have failed to detect some insecure |
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154 | conditions when taint checks are turned on. (Taint checks are used |
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155 | in setuid or setgid scripts, or when explicitly turned on with the |
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156 | C<-T> invocation option.) Although it's unlikely, this may cause a |
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157 | previously-working script to now fail -- which should be construed |
158 | as a blessing, since that indicates a potentially-serious security |
159 | hole was just plugged. |
160 | |
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161 | =head2 New Opcode module and revised Safe module |
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162 | |
163 | A new Opcode module supports the creation, manipulation and |
164 | application of opcode masks. The revised Safe module has a new API |
165 | and is implemented using the new Opcode module. Please read the new |
166 | Opcode and Safe documentation. |
167 | |
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168 | =head2 Embedding improvements |
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169 | |
170 | In older versions of Perl it was not possible to create more than one |
171 | Perl interpreter instance inside a single process without leaking like a |
172 | sieve and/or crashing. The bugs that caused this behavior have all been |
173 | fixed. However, you still must take care when embedding Perl in a C |
174 | program. See the updated perlembed manpage for tips on how to manage |
175 | your interpreters. |
176 | |
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177 | =head2 Internal change: FileHandle class based on IO::* classes |
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178 | |
179 | File handles are now stored internally as type IO::Handle. The |
180 | FileHandle module is still supported for backwards compatibility, but |
181 | it is now merely a front end to the IO::* modules -- specifically, |
182 | IO::Handle, IO::Seekable, and IO::File. We suggest, but do not |
183 | require, that you use the IO::* modules in new code. |
184 | |
185 | In harmony with this change, C<*GLOB{FILEHANDLE}> is now a |
186 | backward-compatible synonym for C<*STDOUT{IO}>. |
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187 | |
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188 | =head2 Internal change: PerlIO abstraction interface |
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189 | |
190 | It is now possible to build Perl with AT&T's sfio IO package |
191 | instead of stdio. See L<perlapio> for more details, and |
192 | the F<INSTALL> file for how to use it. |
193 | |
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194 | =head2 New and changed syntax |
195 | |
196 | =over |
197 | |
198 | =item $coderef->(PARAMS) |
199 | |
200 | A subroutine reference may now be suffixed with an arrow and a |
201 | (possibly empty) parameter list. This syntax denotes a call of the |
202 | referenced subroutine, with the given parameters (if any). |
203 | |
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204 | This new syntax follows the pattern of S<C<$hashref-E<gt>{FOO}>> and |
205 | S<C<$aryref-E<gt>[$foo]>>: You may now write S<C<&$subref($foo)>> as |
206 | S<C<$subref-E<gt>($foo)>>. All of these arrow terms may be chained; |
207 | thus, S<C<&{$table-E<gt>{FOO}}($bar)>> may now be written |
208 | S<C<$table-E<gt>{FOO}-E<gt>($bar)>>. |
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209 | |
210 | =back |
211 | |
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212 | =head2 New and changed builtin constants |
213 | |
214 | =over |
215 | |
216 | =item __PACKAGE__ |
217 | |
218 | The current package name at compile time, or the undefined value if |
219 | there is no current package (due to a C<package;> directive). Like |
220 | C<__FILE__> and C<__LINE__>, C<__PACKAGE__> does I<not> interpolate |
221 | into strings. |
222 | |
223 | =back |
224 | |
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225 | =head2 New and changed builtin variables |
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226 | |
227 | =over |
228 | |
229 | =item $^E |
230 | |
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231 | Extended error message on some platforms. (Also known as |
232 | $EXTENDED_OS_ERROR if you C<use English>). |
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233 | |
234 | =item $^H |
235 | |
236 | The current set of syntax checks enabled by C<use strict>. See the |
237 | documentation of C<strict> for more details. Not actually new, but |
238 | newly documented. |
239 | Because it is intended for internal use by Perl core components, |
240 | there is no C<use English> long name for this variable. |
241 | |
242 | =item $^M |
243 | |
244 | By default, running out of memory it is not trappable. However, if |
245 | compiled for this, Perl may use the contents of C<$^M> as an emergency |
246 | pool after die()ing with this message. Suppose that your Perl were |
247 | compiled with -DEMERGENCY_SBRK and used Perl's malloc. Then |
248 | |
249 | $^M = 'a' x (1<<16); |
250 | |
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251 | would allocate a 64K buffer for use when in emergency. |
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252 | See the F<INSTALL> file for information on how to enable this option. |
253 | As a disincentive to casual use of this advanced feature, |
254 | there is no C<use English> long name for this variable. |
255 | |
256 | =back |
257 | |
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258 | =head2 New and changed builtin functions |
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259 | |
260 | =over |
261 | |
262 | =item delete on slices |
263 | |
264 | This now works. (e.g. C<delete @ENV{'PATH', 'MANPATH'}>) |
265 | |
266 | =item flock |
267 | |
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268 | is now supported on more platforms, prefers fcntl to lockf when |
269 | emulating, and always flushes before (un)locking. |
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270 | |
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271 | =item printf and sprintf |
272 | |
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273 | Perl now implements these functions itself; it doesn't use the C |
274 | library function sprintf() any more, except for floating-point |
275 | numbers, and even then only known flags are allowed. As a result, it |
276 | is now possible to know which conversions and flags will work, and |
277 | what they will do. |
278 | |
279 | The new conversions in Perl's sprintf() are: |
280 | |
281 | %i a synonym for %d |
282 | %p a pointer (the address of the Perl value, in hexadecimal) |
283 | %n special: B<stores> into the next variable in the parameter |
284 | list the number of characters printed so far |
285 | |
286 | The new flags that go between the C<%> and the conversion are: |
287 | |
288 | # prefix octal with "0", hex with "0x" |
289 | h interpret integer as C type "short" or "unsigned short" |
290 | V interpret integer as Perl's standard integer type |
291 | |
292 | Also, where a number would appear in the flags, an asterisk ("*") may |
293 | be used instead, in which case Perl uses the next item in the |
294 | parameter list as the given number (that is, as the field width or |
295 | precision). If a field width obtained through "*" is negative, it has |
296 | the same effect as the '-' flag: left-justification. |
297 | |
298 | See L<perlfunc/sprintf> for a complete list of conversion and flags. |
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299 | |
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300 | =item keys as an lvalue |
301 | |
302 | As an lvalue, C<keys> allows you to increase the number of hash buckets |
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303 | allocated for the given hash. This can gain you a measure of efficiency if |
304 | you know the hash is going to get big. (This is similar to pre-extending |
305 | an array by assigning a larger number to $#array.) If you say |
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306 | |
307 | keys %hash = 200; |
308 | |
309 | then C<%hash> will have at least 200 buckets allocated for it. These |
310 | buckets will be retained even if you do C<%hash = ()>; use C<undef |
311 | %hash> if you want to free the storage while C<%hash> is still in scope. |
312 | You can't shrink the number of buckets allocated for the hash using |
313 | C<keys> in this way (but you needn't worry about doing this by accident, |
314 | as trying has no effect). |
315 | |
316 | =item my() in Control Structures |
317 | |
318 | You can now use my() (with or without the parentheses) in the control |
319 | expressions of control structures such as: |
320 | |
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321 | while (defined(my $line = <>)) { |
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322 | $line = lc $line; |
323 | } continue { |
324 | print $line; |
325 | } |
326 | |
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327 | if ((my $answer = <STDIN>) =~ /^y(es)?$/i) { |
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328 | user_agrees(); |
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329 | } elsif ($answer =~ /^n(o)?$/i) { |
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330 | user_disagrees(); |
331 | } else { |
332 | chomp $answer; |
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333 | die "`$answer' is neither `yes' nor `no'"; |
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334 | } |
335 | |
336 | Also, you can declare a foreach loop control variable as lexical by |
337 | preceding it with the word "my". For example, in: |
338 | |
339 | foreach my $i (1, 2, 3) { |
340 | some_function(); |
341 | } |
342 | |
343 | $i is a lexical variable, and the scope of $i extends to the end of |
344 | the loop, but not beyond it. |
345 | |
346 | Note that you still cannot use my() on global punctuation variables |
347 | such as $_ and the like. |
348 | |
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349 | =item pack() and unpack() |
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350 | |
351 | A new format 'w' represents a BER compressed integer (as defined in |
352 | ASN.1). Its format is a sequence of one or more bytes, each of which |
353 | provides seven bits of the total value, with the most significant |
354 | first. Bit eight of each byte is set, except for the last byte, in |
355 | which bit eight is clear. |
356 | |
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357 | Both pack() and unpack() now fail when their templates contain invalid |
358 | types. (Invalid types used to be ignored.) |
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359 | |
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360 | =item sysseek() |
361 | |
362 | The new sysseek() operator is a variant of seek() that sets and gets the |
363 | file's system read/write position, using the lseek(2) system call. It is |
364 | the only reliable way to seek before using sysread() or syswrite(). Its |
365 | return value is the new position, or the undefined value on failure. |
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366 | |
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367 | =item use VERSION |
368 | |
369 | If the first argument to C<use> is a number, it is treated as a version |
370 | number instead of a module name. If the version of the Perl interpreter |
371 | is less than VERSION, then an error message is printed and Perl exits |
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372 | immediately. Because C<use> occurs at compile time, this check happens |
373 | immediately during the compilation process, unlike C<require VERSION>, |
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374 | which waits until runtime for the check. This is often useful if you |
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375 | need to check the current Perl version before C<use>ing library modules |
376 | which have changed in incompatible ways from older versions of Perl. |
377 | (We try not to do this more than we have to.) |
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378 | |
379 | =item use Module VERSION LIST |
380 | |
381 | If the VERSION argument is present between Module and LIST, then the |
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382 | C<use> will call the VERSION method in class Module with the given |
383 | version as an argument. The default VERSION method, inherited from |
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384 | the UNIVERSAL class, croaks if the given version is larger than the |
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385 | value of the variable $Module::VERSION. (Note that there is not a |
386 | comma after VERSION!) |
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387 | |
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388 | This version-checking mechanism is similar to the one currently used |
389 | in the Exporter module, but it is faster and can be used with modules |
390 | that don't use the Exporter. It is the recommended method for new |
391 | code. |
392 | |
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393 | =item prototype(FUNCTION) |
394 | |
395 | Returns the prototype of a function as a string (or C<undef> if the |
396 | function has no prototype). FUNCTION is a reference to or the name of the |
397 | function whose prototype you want to retrieve. |
398 | (Not actually new; just never documented before.) |
399 | |
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400 | =item srand |
401 | |
402 | The default seed for C<srand>, which used to be C<time>, has been changed. |
403 | Now it's a heady mix of difficult-to-predict system-dependent values, |
404 | which should be sufficient for most everyday purposes. |
405 | |
406 | Previous to version 5.004, calling C<rand> without first calling C<srand> |
407 | would yield the same sequence of random numbers on most or all machines. |
408 | Now, when perl sees that you're calling C<rand> and haven't yet called |
409 | C<srand>, it calls C<srand> with the default seed. You should still call |
410 | C<srand> manually if your code might ever be run on a pre-5.004 system, |
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411 | of course, or if you want a seed other than the default. |
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412 | |
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413 | =item $_ as Default |
414 | |
415 | Functions documented in the Camel to default to $_ now in |
416 | fact do, and all those that do are so documented in L<perlfunc>. |
417 | |
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418 | =item C<m//g> does not reset search position on failure |
419 | |
420 | The C<m//g> match iteration construct used to reset its target string's |
421 | search position (which is visible through the C<pos> operator) when a |
422 | match failed; as a result, the next C<m//g> match would start at the |
423 | beginning of the string). With Perl 5.004, the search position must be |
424 | reset explicitly, as with C<pos $str = 0;>, or by modifying the target |
425 | string. This change in Perl makes it possible to chain matches together |
426 | in conjunction with the C<\G> zero-width assertion. See L<perlop> and |
427 | L<perlre>. |
428 | |
429 | Here is an illustration of what it takes to get the old behavior: |
430 | |
431 | for ( qw(this and that are not what you think you got) ) { |
432 | while ( /(\w*t\w*)/g ) { print "t word is: $1\n" } |
433 | pos = 0; # REQUIRED FOR 5.004 |
434 | while ( /(\w*a\w*)/g ) { print "a word is: $1\n" } |
435 | print "\n"; |
436 | } |
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437 | |
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438 | =item C<m//x> ignores whitespace before ?*+{} |
439 | |
440 | The C<m//x> construct has always been intended to ignore all unescaped |
441 | whitespace. However, before Perl 5.004, whitespace had the effect of |
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442 | escaping repeat modifiers like "*" or "?"; for example, C</a *b/x> was |
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443 | (mis)interpreted as C</a\*b/x>. This bug has been fixed in 5.004. |
444 | |
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445 | =item nested C<sub{}> closures work now |
446 | |
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447 | Prior to the 5.004 release, nested anonymous functions didn't work |
448 | right. They do now. |
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449 | |
450 | =item formats work right on changing lexicals |
451 | |
452 | Just like anonymous functions that contain lexical variables |
453 | that change (like a lexical index variable for a C<foreach> loop), |
454 | formats now work properly. For example, this silently failed |
455 | before, and is fine now: |
456 | |
457 | my $i; |
458 | foreach $i ( 1 .. 10 ) { |
459 | format = |
460 | my i is @# |
461 | $i |
462 | . |
463 | write; |
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464 | } |
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465 | |
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466 | =back |
467 | |
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468 | =head2 New builtin methods |
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469 | |
470 | The C<UNIVERSAL> package automatically contains the following methods that |
471 | are inherited by all other classes: |
472 | |
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473 | =over |
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474 | |
475 | =item isa(CLASS) |
476 | |
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477 | C<isa> returns I<true> if its object is blessed into a subclass of C<CLASS> |
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478 | |
479 | C<isa> is also exportable and can be called as a sub with two arguments. This |
480 | allows the ability to check what a reference points to. Example: |
481 | |
482 | use UNIVERSAL qw(isa); |
483 | |
484 | if(isa($ref, 'ARRAY')) { |
485 | ... |
486 | } |
487 | |
488 | =item can(METHOD) |
489 | |
490 | C<can> checks to see if its object has a method called C<METHOD>, |
491 | if it does then a reference to the sub is returned; if it does not then |
492 | I<undef> is returned. |
493 | |
494 | =item VERSION( [NEED] ) |
495 | |
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496 | C<VERSION> returns the version number of the class (package). If the |
497 | NEED argument is given then it will check that the current version (as |
498 | defined by the $VERSION variable in the given package) not less than |
499 | NEED; it will die if this is not the case. This method is normally |
500 | called as a class method. This method is called automatically by the |
501 | C<VERSION> form of C<use>. |
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502 | |
503 | use A 1.2 qw(some imported subs); |
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504 | # implies: |
505 | A->VERSION(1.2); |
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506 | |
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507 | =back |
508 | |
509 | B<NOTE:> C<can> directly uses Perl's internal code for method lookup, and |
774d564b |
510 | C<isa> uses a very similar method and caching strategy. This may cause |
5f05dabc |
511 | strange effects if the Perl code dynamically changes @ISA in any package. |
512 | |
513 | You may add other methods to the UNIVERSAL class via Perl or XS code. |
514 | You do not need to C<use UNIVERSAL> in order to make these methods |
515 | available to your program. This is necessary only if you wish to |
516 | have C<isa> available as a plain subroutine in the current package. |
517 | |
54310121 |
518 | =head2 TIEHANDLE now supported |
5f05dabc |
519 | |
774d564b |
520 | See L<perltie> for other kinds of tie()s. |
521 | |
5f05dabc |
522 | =over |
523 | |
524 | =item TIEHANDLE classname, LIST |
525 | |
526 | This is the constructor for the class. That means it is expected to |
527 | return an object of some sort. The reference can be used to |
528 | hold some internal information. |
529 | |
2ae324a7 |
530 | sub TIEHANDLE { |
531 | print "<shout>\n"; |
532 | my $i; |
774d564b |
533 | return bless \$i, shift; |
534 | } |
5f05dabc |
535 | |
536 | =item PRINT this, LIST |
537 | |
538 | This method will be triggered every time the tied handle is printed to. |
539 | Beyond its self reference it also expects the list that was passed to |
540 | the print function. |
541 | |
2ae324a7 |
542 | sub PRINT { |
543 | $r = shift; |
544 | $$r++; |
774d564b |
545 | return print join( $, => map {uc} @_), $\; |
546 | } |
5f05dabc |
547 | |
46fc3d4c |
548 | =item PRINTF this, LIST |
549 | |
550 | This method will be triggered every time the tied handle is printed to |
551 | with the C<printf()> function. |
552 | Beyond its self reference it also expects the format and list that was |
553 | passed to the printf function. |
554 | |
555 | sub PRINTF { |
556 | shift; |
557 | my $fmt = shift; |
558 | print sprintf($fmt, @_)."\n"; |
559 | } |
560 | |
2ae324a7 |
561 | =item READ this LIST |
562 | |
563 | This method will be called when the handle is read from via the C<read> |
564 | or C<sysread> functions. |
565 | |
566 | sub READ { |
567 | $r = shift; |
568 | my($buf,$len,$offset) = @_; |
569 | print "READ called, \$buf=$buf, \$len=$len, \$offset=$offset"; |
570 | } |
571 | |
5f05dabc |
572 | =item READLINE this |
573 | |
574 | This method will be called when the handle is read from. The method |
575 | should return undef when there is no more data. |
576 | |
2ae324a7 |
577 | sub READLINE { |
578 | $r = shift; |
579 | return "PRINT called $$r times\n" |
774d564b |
580 | } |
5f05dabc |
581 | |
2ae324a7 |
582 | =item GETC this |
583 | |
584 | This method will be called when the C<getc> function is called. |
585 | |
586 | sub GETC { print "Don't GETC, Get Perl"; return "a"; } |
587 | |
5f05dabc |
588 | =item DESTROY this |
589 | |
590 | As with the other types of ties, this method will be called when the |
591 | tied handle is about to be destroyed. This is useful for debugging and |
592 | possibly for cleaning up. |
593 | |
2ae324a7 |
594 | sub DESTROY { |
774d564b |
595 | print "</shout>\n"; |
596 | } |
5f05dabc |
597 | |
598 | =back |
599 | |
54310121 |
600 | =head2 Malloc enhancements |
aa689395 |
601 | |
2ae324a7 |
602 | Four new compilation flags are recognized by malloc.c. (They have no |
603 | effect if perl is compiled with system malloc().) |
604 | |
605 | =over |
606 | |
607 | =item -DDEBUGGING_MSTATS |
608 | |
609 | If perl is compiled with C<DEBUGGING_MSTATS> defined, you can print |
610 | memory statistics at runtime by running Perl thusly: |
aa689395 |
611 | |
612 | env PERL_DEBUG_MSTATS=2 perl your_script_here |
613 | |
614 | The value of 2 means to print statistics after compilation and on |
615 | exit; with a value of 1, the statistics ares printed only on exit. |
616 | (If you want the statistics at an arbitrary time, you'll need to |
617 | install the optional module Devel::Peek.) |
618 | |
aa689395 |
619 | =item -DEMERGENCY_SBRK |
620 | |
621 | If this macro is defined, running out of memory need not be a fatal |
622 | error: a memory pool can allocated by assigning to the special |
623 | variable C<$^M>. See L<"$^M">. |
774d564b |
624 | |
aa689395 |
625 | =item -DPACK_MALLOC |
626 | |
627 | Perl memory allocation is by bucket with sizes close to powers of two. |
628 | Because of these malloc overhead may be big, especially for data of |
629 | size exactly a power of two. If C<PACK_MALLOC> is defined, perl uses |
630 | a slightly different algorithm for small allocations (up to 64 bytes |
631 | long), which makes it possible to have overhead down to 1 byte for |
632 | allocations which are powers of two (and appear quite often). |
633 | |
634 | Expected memory savings (with 8-byte alignment in C<alignbytes>) is |
635 | about 20% for typical Perl usage. Expected slowdown due to additional |
636 | malloc overhead is in fractions of a percent (hard to measure, because |
637 | of the effect of saved memory on speed). |
638 | |
639 | =item -DTWO_POT_OPTIMIZE |
640 | |
641 | Similarly to C<PACK_MALLOC>, this macro improves allocations of data |
642 | with size close to a power of two; but this works for big allocations |
643 | (starting with 16K by default). Such allocations are typical for big |
644 | hashes and special-purpose scripts, especially image processing. |
645 | |
646 | On recent systems, the fact that perl requires 2M from system for 1M |
647 | allocation will not affect speed of execution, since the tail of such |
648 | a chunk is not going to be touched (and thus will not require real |
649 | memory). However, it may result in a premature out-of-memory error. |
650 | So if you will be manipulating very large blocks with sizes close to |
651 | powers of two, it would be wise to define this macro. |
652 | |
653 | Expected saving of memory is 0-100% (100% in applications which |
654 | require most memory in such 2**n chunks); expected slowdown is |
655 | negligible. |
656 | |
657 | =back |
658 | |
54310121 |
659 | =head2 Miscellaneous efficiency enhancements |
774d564b |
660 | |
661 | Functions that have an empty prototype and that do nothing but return |
662 | a fixed value are now inlined (e.g. C<sub PI () { 3.14159 }>). |
663 | |
aa689395 |
664 | Each unique hash key is only allocated once, no matter how many hashes |
665 | have an entry with that key. So even if you have 100 copies of the |
68dc0745 |
666 | same hash, the hash keys never have to be reallocated. |
aa689395 |
667 | |
5f05dabc |
668 | =head1 Pragmata |
669 | |
54310121 |
670 | Six new pragmatic modules exist: |
5f05dabc |
671 | |
672 | =over |
673 | |
54310121 |
674 | =item use autouse MODULE => qw(sub1 sub2 sub3) |
675 | |
676 | Defers C<require MODULE> until someone calls one of the specified |
677 | subroutines (which must be exported by MODULE). This pragma should be |
678 | used with caution, and only when necessary. |
679 | |
5f05dabc |
680 | =item use blib |
681 | |
774d564b |
682 | =item use blib 'dir' |
683 | |
5f05dabc |
684 | Looks for MakeMaker-like I<'blib'> directory structure starting in |
685 | I<dir> (or current directory) and working back up to five levels of |
686 | parent directories. |
687 | |
688 | Intended for use on command line with B<-M> option as a way of testing |
689 | arbitrary scripts against an uninstalled version of a package. |
690 | |
54310121 |
691 | =item use constant NAME => VALUE |
692 | |
693 | Provides a convenient interface for creating compile-time constants, |
694 | See L<perlsub/"Constant Functions">. |
695 | |
5f05dabc |
696 | =item use locale |
697 | |
698 | Tells the compiler to enable (or disable) the use of POSIX locales for |
54310121 |
699 | builtin operations. |
5f05dabc |
700 | |
701 | When C<use locale> is in effect, the current LC_CTYPE locale is used |
702 | for regular expressions and case mapping; LC_COLLATE for string |
703 | ordering; and LC_NUMERIC for numeric formating in printf and sprintf |
704 | (but B<not> in print). LC_NUMERIC is always used in write, since |
705 | lexical scoping of formats is problematic at best. |
706 | |
707 | Each C<use locale> or C<no locale> affects statements to the end of |
708 | the enclosing BLOCK or, if not inside a BLOCK, to the end of the |
709 | current file. Locales can be switched and queried with |
710 | POSIX::setlocale(). |
711 | |
712 | See L<perllocale> for more information. |
713 | |
714 | =item use ops |
715 | |
7cfe7857 |
716 | Disable unsafe opcodes, or any named opcodes, when compiling Perl code. |
5f05dabc |
717 | |
ff0cee69 |
718 | =item use vmsish |
719 | |
720 | Enable VMS-specific language features. Currently, there are three |
aa689395 |
721 | VMS-specific features available: 'status', which makes C<$?> and |
ff0cee69 |
722 | C<system> return genuine VMS status values instead of emulating POSIX; |
723 | 'exit', which makes C<exit> take a genuine VMS status value instead of |
724 | assuming that C<exit 1> is an error; and 'time', which makes all times |
725 | relative to the local time zone, in the VMS tradition. |
726 | |
5f05dabc |
727 | =back |
728 | |
729 | =head1 Modules |
730 | |
5cd24f17 |
731 | =head2 Required Updates |
732 | |
733 | Though Perl 5.004 is compatible with almost all modules that work |
734 | with Perl 5.003, there are a few exceptions: |
735 | |
736 | Module Required Version for Perl 5.004 |
737 | ------ ------------------------------- |
137443ea |
738 | Filter Filter-1.12 |
739 | LWP libwww-perl-5.08 |
5cd24f17 |
740 | Tk Tk400.202 (-w makes noise) |
741 | |
137443ea |
742 | Also, the majordomo mailing list program, version 1.94.1, doesn't work |
743 | with Perl 5.004 (nor with perl 4), because it executes an invalid |
744 | regular expression. This bug is fixed in majordomo version 1.94.2. |
745 | |
54310121 |
746 | =head2 Installation directories |
f86702cc |
747 | |
748 | The I<installperl> script now places the Perl source files for |
749 | extensions in the architecture-specific library directory, which is |
750 | where the shared libraries for extensions have always been. This |
751 | change is intended to allow administrators to keep the Perl 5.004 |
752 | library directory unchanged from a previous version, without running |
753 | the risk of binary incompatibility between extensions' Perl source and |
754 | shared libraries. |
755 | |
54310121 |
756 | =head2 Module information summary |
5f05dabc |
757 | |
774d564b |
758 | Brand new modules, arranged by topic rather than strictly |
759 | alphabetically: |
760 | |
137443ea |
761 | CGI.pm Web server interface ("Common Gateway Interface") |
762 | CGI/Apache.pm Support for Apache's Perl module |
763 | CGI/Carp.pm Log server errors with helpful context |
764 | CGI/Fast.pm Support for FastCGI (persistent server process) |
765 | CGI/Push.pm Support for server push |
766 | CGI/Switch.pm Simple interface for multiple server types |
767 | |
768 | CPAN Interface to Comprehensive Perl Archive Network |
769 | CPAN::FirstTime Utility for creating CPAN configuration file |
770 | CPAN::Nox Runs CPAN while avoiding compiled extensions |
5f05dabc |
771 | |
772 | IO.pm Top-level interface to IO::* classes |
773 | IO/File.pm IO::File extension Perl module |
774 | IO/Handle.pm IO::Handle extension Perl module |
775 | IO/Pipe.pm IO::Pipe extension Perl module |
776 | IO/Seekable.pm IO::Seekable extension Perl module |
777 | IO/Select.pm IO::Select extension Perl module |
778 | IO/Socket.pm IO::Socket extension Perl module |
779 | |
780 | Opcode.pm Disable named opcodes when compiling Perl code |
781 | |
782 | ExtUtils/Embed.pm Utilities for embedding Perl in C programs |
783 | ExtUtils/testlib.pm Fixes up @INC to use just-built extension |
784 | |
5f05dabc |
785 | FindBin.pm Find path of currently executing program |
786 | |
8cc95fdb |
787 | Class/Struct.pm Declare struct-like datatypes as Perl classes |
46fc3d4c |
788 | File/stat.pm By-name interface to Perl's builtin stat |
789 | Net/hostent.pm By-name interface to Perl's builtin gethost* |
790 | Net/netent.pm By-name interface to Perl's builtin getnet* |
791 | Net/protoent.pm By-name interface to Perl's builtin getproto* |
792 | Net/servent.pm By-name interface to Perl's builtin getserv* |
793 | Time/gmtime.pm By-name interface to Perl's builtin gmtime |
794 | Time/localtime.pm By-name interface to Perl's builtin localtime |
8cc95fdb |
795 | Time/tm.pm Internal object for Time::{gm,local}time |
46fc3d4c |
796 | User/grent.pm By-name interface to Perl's builtin getgr* |
797 | User/pwent.pm By-name interface to Perl's builtin getpw* |
5f05dabc |
798 | |
774d564b |
799 | Tie/RefHash.pm Base class for tied hashes with references as keys |
7a4c00b4 |
800 | |
5f05dabc |
801 | UNIVERSAL.pm Base class for *ALL* classes |
802 | |
54310121 |
803 | =head2 Fcntl |
804 | |
805 | New constants in the existing Fcntl modules are now supported, |
806 | provided that your operating system happens to support them: |
807 | |
808 | F_GETOWN F_SETOWN |
809 | O_ASYNC O_DEFER O_DSYNC O_FSYNC O_SYNC |
810 | O_EXLOCK O_SHLOCK |
811 | |
812 | These constants are intended for use with the Perl operators sysopen() |
813 | and fcntl() and the basic database modules like SDBM_File. For the |
814 | exact meaning of these and other Fcntl constants please refer to your |
815 | operating system's documentation for fcntl() and open(). |
816 | |
817 | In addition, the Fcntl module now provides these constants for use |
818 | with the Perl operator flock(): |
819 | |
820 | LOCK_SH LOCK_EX LOCK_NB LOCK_UN |
821 | |
822 | These constants are defined in all environments (because where there is |
823 | no flock() system call, Perl emulates it). However, for historical |
824 | reasons, these constants are not exported unless they are explicitly |
825 | requested with the ":flock" tag (e.g. C<use Fcntl ':flock'>). |
826 | |
5f05dabc |
827 | =head2 IO |
828 | |
829 | The IO module provides a simple mechanism to load all of the IO modules at one |
830 | go. Currently this includes: |
831 | |
832 | IO::Handle |
833 | IO::Seekable |
834 | IO::File |
835 | IO::Pipe |
836 | IO::Socket |
837 | |
838 | For more information on any of these modules, please see its |
839 | respective documentation. |
840 | |
841 | =head2 Math::Complex |
842 | |
843 | The Math::Complex module has been totally rewritten, and now supports |
844 | more operations. These are overloaded: |
845 | |
846 | + - * / ** <=> neg ~ abs sqrt exp log sin cos atan2 "" (stringify) |
847 | |
848 | And these functions are now exported: |
849 | |
850 | pi i Re Im arg |
5cd24f17 |
851 | log10 logn ln cbrt root |
852 | tan |
853 | csc sec cot |
854 | asin acos atan |
855 | acsc asec acot |
856 | sinh cosh tanh |
857 | csch sech coth |
858 | asinh acosh atanh |
859 | acsch asech acoth |
5f05dabc |
860 | cplx cplxe |
861 | |
5aabfad6 |
862 | =head2 Math::Trig |
863 | |
5cd24f17 |
864 | This new module provides a simpler interface to parts of Math::Complex for |
5aabfad6 |
865 | those who need trigonometric functions only for real numbers. |
866 | |
0a753a76 |
867 | =head2 DB_File |
868 | |
869 | There have been quite a few changes made to DB_File. Here are a few of |
870 | the highlights: |
871 | |
872 | =over |
873 | |
874 | =item * |
875 | |
876 | Fixed a handful of bugs. |
877 | |
878 | =item * |
879 | |
880 | By public demand, added support for the standard hash function exists(). |
881 | |
882 | =item * |
883 | |
884 | Made it compatible with Berkeley DB 1.86. |
885 | |
886 | =item * |
887 | |
888 | Made negative subscripts work with RECNO interface. |
889 | |
890 | =item * |
891 | |
892 | Changed the default flags from O_RDWR to O_CREAT|O_RDWR and the default |
893 | mode from 0640 to 0666. |
894 | |
895 | =item * |
896 | |
897 | Made DB_File automatically import the open() constants (O_RDWR, |
898 | O_CREAT etc.) from Fcntl, if available. |
899 | |
900 | =item * |
901 | |
902 | Updated documentation. |
903 | |
904 | =back |
905 | |
906 | Refer to the HISTORY section in DB_File.pm for a complete list of |
907 | changes. Everything after DB_File 1.01 has been added since 5.003. |
908 | |
909 | =head2 Net::Ping |
910 | |
911 | Major rewrite - support added for both udp echo and real icmp pings. |
912 | |
54310121 |
913 | =head2 Object-oriented overrides for builtin operators |
5f05dabc |
914 | |
54310121 |
915 | Many of the Perl builtins returning lists now have |
5f05dabc |
916 | object-oriented overrides. These are: |
917 | |
918 | File::stat |
919 | Net::hostent |
920 | Net::netent |
921 | Net::protoent |
922 | Net::servent |
923 | Time::gmtime |
924 | Time::localtime |
925 | User::grent |
926 | User::pwent |
927 | |
928 | For example, you can now say |
929 | |
930 | use File::stat; |
931 | use User::pwent; |
932 | $his = (stat($filename)->st_uid == pwent($whoever)->pw_uid); |
933 | |
774d564b |
934 | =head1 Utility Changes |
5f05dabc |
935 | |
774d564b |
936 | =head2 xsubpp |
5f05dabc |
937 | |
0a753a76 |
938 | =over |
939 | |
774d564b |
940 | =item C<void> XSUBs now default to returning nothing |
941 | |
942 | Due to a documentation/implementation bug in previous versions of |
943 | Perl, XSUBs with a return type of C<void> have actually been |
944 | returning one value. Usually that value was the GV for the XSUB, |
945 | but sometimes it was some already freed or reused value, which would |
946 | sometimes lead to program failure. |
947 | |
948 | In Perl 5.004, if an XSUB is declared as returning C<void>, it |
949 | actually returns no value, i.e. an empty list (though there is a |
950 | backward-compatibility exception; see below). If your XSUB really |
951 | does return an SV, you should give it a return type of C<SV *>. |
952 | |
953 | For backward compatibility, I<xsubpp> tries to guess whether a |
954 | C<void> XSUB is really C<void> or if it wants to return an C<SV *>. |
955 | It does so by examining the text of the XSUB: if I<xsubpp> finds |
956 | what looks like an assignment to C<ST(0)>, it assumes that the |
957 | XSUB's return type is really C<SV *>. |
5f05dabc |
958 | |
0a753a76 |
959 | =back |
960 | |
961 | =head1 C Language API Changes |
962 | |
963 | =over |
964 | |
965 | =item C<gv_fetchmethod> and C<perl_call_sv> |
966 | |
967 | The C<gv_fetchmethod> function finds a method for an object, just like |
968 | in Perl 5.003. The GV it returns may be a method cache entry. |
969 | However, in Perl 5.004, method cache entries are not visible to users; |
970 | therefore, they can no longer be passed directly to C<perl_call_sv>. |
971 | Instead, you should use the C<GvCV> macro on the GV to extract its CV, |
972 | and pass the CV to C<perl_call_sv>. |
973 | |
974 | The most likely symptom of passing the result of C<gv_fetchmethod> to |
975 | C<perl_call_sv> is Perl's producing an "Undefined subroutine called" |
976 | error on the I<second> call to a given method (since there is no cache |
977 | on the first call). |
978 | |
137443ea |
979 | =item C<perl_eval_pv> |
980 | |
8903cb82 |
981 | A new function handy for eval'ing strings of Perl code inside C code. |
137443ea |
982 | This function returns the value from the eval statement, which can |
983 | be used instead of fetching globals from the symbol table. See |
984 | L<perlguts>, L<perlembed> and L<perlcall> for details and examples. |
985 | |
1e422769 |
986 | =item Extended API for manipulating hashes |
987 | |
988 | Internal handling of hash keys has changed. The old hashtable API is |
989 | still fully supported, and will likely remain so. The additions to the |
990 | API allow passing keys as C<SV*>s, so that C<tied> hashes can be given |
54310121 |
991 | real scalars as keys rather than plain strings (nontied hashes still |
1e422769 |
992 | can only use strings as keys). New extensions must use the new hash |
993 | access functions and macros if they wish to use C<SV*> keys. These |
994 | additions also make it feasible to manipulate C<HE*>s (hash entries), |
995 | which can be more efficient. See L<perlguts> for details. |
996 | |
0a753a76 |
997 | =back |
998 | |
5f05dabc |
999 | =head1 Documentation Changes |
1000 | |
1001 | Many of the base and library pods were updated. These |
1002 | new pods are included in section 1: |
1003 | |
0a753a76 |
1004 | =over |
5f05dabc |
1005 | |
774d564b |
1006 | =item L<perldelta> |
5f05dabc |
1007 | |
71be2cbc |
1008 | This document. |
5f05dabc |
1009 | |
71be2cbc |
1010 | =item L<perllocale> |
5f05dabc |
1011 | |
71be2cbc |
1012 | Locale support (internationalization and localization). |
5f05dabc |
1013 | |
1014 | =item L<perltoot> |
1015 | |
1016 | Tutorial on Perl OO programming. |
1017 | |
71be2cbc |
1018 | =item L<perlapio> |
1019 | |
1020 | Perl internal IO abstraction interface. |
1021 | |
5f05dabc |
1022 | =item L<perldebug> |
1023 | |
1024 | Although not new, this has been massively updated. |
1025 | |
1026 | =item L<perlsec> |
1027 | |
1028 | Although not new, this has been massively updated. |
1029 | |
1030 | =back |
1031 | |
1032 | =head1 New Diagnostics |
1033 | |
1034 | Several new conditions will trigger warnings that were |
1035 | silent before. Some only affect certain platforms. |
2ae324a7 |
1036 | The following new warnings and errors outline these. |
774d564b |
1037 | These messages are classified as follows (listed in |
1038 | increasing order of desperation): |
1039 | |
1040 | (W) A warning (optional). |
1041 | (D) A deprecation (optional). |
1042 | (S) A severe warning (mandatory). |
1043 | (F) A fatal error (trappable). |
1044 | (P) An internal error you should never see (trappable). |
54310121 |
1045 | (X) A very fatal error (nontrappable). |
774d564b |
1046 | (A) An alien error message (not generated by Perl). |
5f05dabc |
1047 | |
0a753a76 |
1048 | =over |
5f05dabc |
1049 | |
1050 | =item "my" variable %s masks earlier declaration in same scope |
1051 | |
1052 | (S) A lexical variable has been redeclared in the same scope, effectively |
1053 | eliminating all access to the previous instance. This is almost always |
1054 | a typographical error. Note that the earlier variable will still exist |
1055 | until the end of the scope or until all closure referents to it are |
1056 | destroyed. |
1057 | |
774d564b |
1058 | =item %s argument is not a HASH element or slice |
1059 | |
1060 | (F) The argument to delete() must be either a hash element, such as |
1061 | |
1062 | $foo{$bar} |
1063 | $ref->[12]->{"susie"} |
1064 | |
1065 | or a hash slice, such as |
1066 | |
1067 | @foo{$bar, $baz, $xyzzy} |
1068 | @{$ref->[12]}{"susie", "queue"} |
1069 | |
5f05dabc |
1070 | =item Allocation too large: %lx |
1071 | |
54310121 |
1072 | (X) You can't allocate more than 64K on an MS-DOS machine. |
5f05dabc |
1073 | |
1074 | =item Allocation too large |
1075 | |
1076 | (F) You can't allocate more than 2^31+"small amount" bytes. |
1077 | |
54310121 |
1078 | =item Applying %s to %s will act on scalar(%s) |
1079 | |
1080 | (W) The pattern match (//), substitution (s///), and translation (tr///) |
1081 | operators work on scalar values. If you apply one of them to an array |
1082 | or a hash, it will convert the array or hash to a scalar value -- the |
1083 | length of an array, or the population info of a hash -- and then work on |
1084 | that scalar value. This is probably not what you meant to do. See |
1085 | L<perlfunc/grep> and L<perlfunc/map> for alternatives. |
1086 | |
1087 | =item Attempt to free nonexistent shared string |
5f05dabc |
1088 | |
1089 | (P) Perl maintains a reference counted internal table of strings to |
1090 | optimize the storage and access of hash keys and other strings. This |
1091 | indicates someone tried to decrement the reference count of a string |
1092 | that can no longer be found in the table. |
1093 | |
1094 | =item Attempt to use reference as lvalue in substr |
1095 | |
1096 | (W) You supplied a reference as the first argument to substr() used |
1097 | as an lvalue, which is pretty strange. Perhaps you forgot to |
1098 | dereference it first. See L<perlfunc/substr>. |
1099 | |
774d564b |
1100 | =item Can't use bareword ("%s") as %s ref while "strict refs" in use |
1101 | |
1102 | (F) Only hard references are allowed by "strict refs". Symbolic references |
1103 | are disallowed. See L<perlref>. |
1104 | |
54310121 |
1105 | =item Cannot resolve method `%s' overloading `%s' in package `%s' |
1106 | |
1107 | (P) Internal error trying to resolve overloading specified by a method |
1108 | name (as opposed to a subroutine reference). |
1109 | |
774d564b |
1110 | =item Constant subroutine %s redefined |
1111 | |
1112 | (S) You redefined a subroutine which had previously been eligible for |
dc848c6f |
1113 | inlining. See L<perlsub/"Constant Functions"> for commentary and |
54310121 |
1114 | workarounds. |
1115 | |
1116 | =item Constant subroutine %s undefined |
1117 | |
1118 | (S) You undefined a subroutine which had previously been eligible for |
774d564b |
1119 | inlining. See L<perlsub/"Constant Functions"> for commentary and |
1120 | workarounds. |
1121 | |
54310121 |
1122 | =item Copy method did not return a reference |
1123 | |
1124 | (F) The method which overloads "=" is buggy. See L<overload/Copy Constructor>. |
1125 | |
774d564b |
1126 | =item Died |
1127 | |
1128 | (F) You passed die() an empty string (the equivalent of C<die "">) or |
1129 | you called it with no args and both C<$@> and C<$_> were empty. |
1130 | |
54310121 |
1131 | =item Exiting pseudo-block via %s |
1132 | |
1133 | (W) You are exiting a rather special block construct (like a sort block or |
1134 | subroutine) by unconventional means, such as a goto, or a loop control |
1135 | statement. See L<perlfunc/sort>. |
1136 | |
8903cb82 |
1137 | =item Identifier too long |
1138 | |
1139 | (F) Perl limits identifiers (names for variables, functions, etc.) to |
1140 | 252 characters for simple names, somewhat more for compound names (like |
1141 | C<$A::B>). You've exceeded Perl's limits. Future versions of Perl are |
1142 | likely to eliminate these arbitrary limitations. |
1143 | |
54310121 |
1144 | =item Illegal character %s (carriage return) |
1145 | |
1146 | (F) A carriage return character was found in the input. This is an |
1147 | error, and not a warning, because carriage return characters can break |
1148 | multi-line strings, including here documents (e.g., C<print E<lt>E<lt>EOF;>). |
1149 | |
1150 | =item Illegal switch in PERL5OPT: %s |
1151 | |
1152 | (X) The PERL5OPT environment variable may only be used to set the |
1153 | following switches: B<-[DIMUdmw]>. |
1154 | |
5f05dabc |
1155 | =item Integer overflow in hex number |
1156 | |
1157 | (S) The literal hex number you have specified is too big for your |
1158 | architecture. On a 32-bit architecture the largest hex literal is |
1159 | 0xFFFFFFFF. |
1160 | |
1161 | =item Integer overflow in octal number |
1162 | |
1163 | (S) The literal octal number you have specified is too big for your |
1164 | architecture. On a 32-bit architecture the largest octal literal is |
1165 | 037777777777. |
1166 | |
5cd24f17 |
1167 | =item internal error: glob failed |
1168 | |
1169 | (P) Something went wrong with the external program(s) used for C<glob> |
1170 | and C<E<lt>*.cE<gt>>. This may mean that your csh (C shell) is |
1171 | broken. If so, you should change all of the csh-related variables in |
1172 | config.sh: If you have tcsh, make the variables refer to it as if it |
1173 | were csh (e.g. C<full_csh='/usr/bin/tcsh'>); otherwise, make them all |
1174 | empty (except that C<d_csh> should be C<'undef'>) so that Perl will |
1175 | think csh is missing. In either case, after editing config.sh, run |
1176 | C<./Configure -S> and rebuild Perl. |
1177 | |
878e08df |
1178 | =item Invalid conversion in %s: "%s" |
1179 | |
1180 | (W) Perl does not understand the given format conversion. |
1181 | See L<perlfunc/sprintf>. |
1182 | |
8903cb82 |
1183 | =item Invalid type in pack: '%s' |
1184 | |
1185 | (F) The given character is not a valid pack type. See L<perlfunc/pack>. |
1186 | |
1187 | =item Invalid type in unpack: '%s' |
1188 | |
1189 | (F) The given character is not a valid unpack type. See L<perlfunc/unpack>. |
1190 | |
774d564b |
1191 | =item Name "%s::%s" used only once: possible typo |
1192 | |
1193 | (W) Typographical errors often show up as unique variable names. |
1194 | If you had a good reason for having a unique name, then just mention |
1195 | it again somehow to suppress the message (the C<use vars> pragma is |
1196 | provided for just this purpose). |
1197 | |
5f05dabc |
1198 | =item Null picture in formline |
1199 | |
1200 | (F) The first argument to formline must be a valid format picture |
1201 | specification. It was found to be empty, which probably means you |
1202 | supplied it an uninitialized value. See L<perlform>. |
1203 | |
1204 | =item Offset outside string |
1205 | |
1206 | (F) You tried to do a read/write/send/recv operation with an offset |
1207 | pointing outside the buffer. This is difficult to imagine. |
1208 | The sole exception to this is that C<sysread()>ing past the buffer |
1209 | will extend the buffer and zero pad the new area. |
1210 | |
1211 | =item Out of memory! |
1212 | |
1213 | (X|F) The malloc() function returned 0, indicating there was insufficient |
1214 | remaining memory (or virtual memory) to satisfy the request. |
1215 | |
1216 | The request was judged to be small, so the possibility to trap it |
1217 | depends on the way Perl was compiled. By default it is not trappable. |
1218 | However, if compiled for this, Perl may use the contents of C<$^M> as |
1219 | an emergency pool after die()ing with this message. In this case the |
1220 | error is trappable I<once>. |
1221 | |
1222 | =item Out of memory during request for %s |
1223 | |
1224 | (F) The malloc() function returned 0, indicating there was insufficient |
1225 | remaining memory (or virtual memory) to satisfy the request. However, |
1226 | the request was judged large enough (compile-time default is 64K), so |
1227 | a possibility to shut down by trapping this error is granted. |
1228 | |
878e08df |
1229 | =item panic: frexp |
1230 | |
1231 | (P) The library function frexp() failed, making printf("%f") impossible. |
1232 | |
5f05dabc |
1233 | =item Possible attempt to put comments in qw() list |
1234 | |
774d564b |
1235 | (W) qw() lists contain items separated by whitespace; as with literal |
1236 | strings, comment characters are not ignored, but are instead treated |
1237 | as literal data. (You may have used different delimiters than the |
1238 | exclamation marks parentheses shown here; braces are also frequently |
1239 | used.) |
1240 | |
1241 | You probably wrote something like this: |
5f05dabc |
1242 | |
2ae324a7 |
1243 | @list = qw( |
774d564b |
1244 | a # a comment |
5f05dabc |
1245 | b # another comment |
774d564b |
1246 | ); |
5f05dabc |
1247 | |
1248 | when you should have written this: |
1249 | |
774d564b |
1250 | @list = qw( |
2ae324a7 |
1251 | a |
5f05dabc |
1252 | b |
774d564b |
1253 | ); |
1254 | |
1255 | If you really want comments, build your list the |
1256 | old-fashioned way, with quotes and commas: |
1257 | |
1258 | @list = ( |
1259 | 'a', # a comment |
1260 | 'b', # another comment |
1261 | ); |
5f05dabc |
1262 | |
1263 | =item Possible attempt to separate words with commas |
1264 | |
774d564b |
1265 | (W) qw() lists contain items separated by whitespace; therefore commas |
1266 | aren't needed to separate the items. (You may have used different |
1267 | delimiters than the parentheses shown here; braces are also frequently |
1268 | used.) |
5f05dabc |
1269 | |
2ae324a7 |
1270 | You probably wrote something like this: |
5f05dabc |
1271 | |
774d564b |
1272 | qw! a, b, c !; |
1273 | |
1274 | which puts literal commas into some of the list items. Write it without |
1275 | commas if you don't want them to appear in your data: |
1276 | |
1277 | qw! a b c !; |
5f05dabc |
1278 | |
774d564b |
1279 | =item Scalar value @%s{%s} better written as $%s{%s} |
1280 | |
1281 | (W) You've used a hash slice (indicated by @) to select a single element of |
1282 | a hash. Generally it's better to ask for a scalar value (indicated by $). |
1283 | The difference is that C<$foo{&bar}> always behaves like a scalar, both when |
1284 | assigning to it and when evaluating its argument, while C<@foo{&bar}> behaves |
1285 | like a list when you assign to it, and provides a list context to its |
1286 | subscript, which can do weird things if you're expecting only one subscript. |
5f05dabc |
1287 | |
54310121 |
1288 | =item Stub found while resolving method `%s' overloading `%s' in package `%s' |
1289 | |
1290 | (P) Overloading resolution over @ISA tree may be broken by importing stubs. |
1291 | Stubs should never be implicitely created, but explicit calls to C<can> |
1292 | may break this. |
1293 | |
1294 | =item Too late for "B<-T>" option |
1295 | |
1296 | (X) The #! line (or local equivalent) in a Perl script contains the |
1297 | B<-T> option, but Perl was not invoked with B<-T> in its argument |
1298 | list. This is an error because, by the time Perl discovers a B<-T> in |
1299 | a script, it's too late to properly taint everything from the |
1300 | environment. So Perl gives up. |
1301 | |
5f05dabc |
1302 | =item untie attempted while %d inner references still exist |
1303 | |
1304 | (W) A copy of the object returned from C<tie> (or C<tied>) was still |
1305 | valid when C<untie> was called. |
1306 | |
54310121 |
1307 | =item Unrecognized character %s |
1308 | |
1309 | (F) The Perl parser has no idea what to do with the specified character |
1310 | in your Perl script (or eval). Perhaps you tried to run a compressed |
1311 | script, a binary program, or a directory as a Perl program. |
1312 | |
1313 | =item Unsupported function fork |
1314 | |
1315 | (F) Your version of executable does not support forking. |
1316 | |
1317 | Note that under some systems, like OS/2, there may be different flavors of |
1318 | Perl executables, some of which may support fork, some not. Try changing |
1319 | the name you call Perl by to C<perl_>, C<perl__>, and so on. |
1320 | |
5cd24f17 |
1321 | =item Use of "$$<digit>" to mean "${$}<digit>" is deprecated |
1322 | |
1323 | (D) Perl versions before 5.004 misinterpreted any type marker followed |
1324 | by "$" and a digit. For example, "$$0" was incorrectly taken to mean |
1325 | "${$}0" instead of "${$0}". This bug is (mostly) fixed in Perl 5.004. |
1326 | |
1327 | However, the developers of Perl 5.004 could not fix this bug completely, |
1328 | because at least two widely-used modules depend on the old meaning of |
1329 | "$$0" in a string. So Perl 5.004 still interprets "$$<digit>" in the |
1330 | old (broken) way inside strings; but it generates this message as a |
1331 | warning. And in Perl 5.005, this special treatment will cease. |
1332 | |
54310121 |
1333 | =item Value of %s can be "0"; test with defined() |
774d564b |
1334 | |
54310121 |
1335 | (W) In a conditional expression, you used <HANDLE>, <*> (glob), C<each()>, |
1336 | or C<readdir()> as a boolean value. Each of these constructs can return a |
1337 | value of "0"; that would make the conditional expression false, which is |
1338 | probably not what you intended. When using these constructs in conditional |
1339 | expressions, test their values with the C<defined> operator. |
774d564b |
1340 | |
1341 | =item Variable "%s" may be unavailable |
1342 | |
1343 | (W) An inner (nested) I<anonymous> subroutine is inside a I<named> |
1344 | subroutine, and outside that is another subroutine; and the anonymous |
1345 | (innermost) subroutine is referencing a lexical variable defined in |
1346 | the outermost subroutine. For example: |
1347 | |
1348 | sub outermost { my $a; sub middle { sub { $a } } } |
1349 | |
1350 | If the anonymous subroutine is called or referenced (directly or |
1351 | indirectly) from the outermost subroutine, it will share the variable |
1352 | as you would expect. But if the anonymous subroutine is called or |
1353 | referenced when the outermost subroutine is not active, it will see |
1354 | the value of the shared variable as it was before and during the |
1355 | *first* call to the outermost subroutine, which is probably not what |
1356 | you want. |
1357 | |
1358 | In these circumstances, it is usually best to make the middle |
1359 | subroutine anonymous, using the C<sub {}> syntax. Perl has specific |
1360 | support for shared variables in nested anonymous subroutines; a named |
1361 | subroutine in between interferes with this feature. |
1362 | |
1363 | =item Variable "%s" will not stay shared |
1364 | |
1365 | (W) An inner (nested) I<named> subroutine is referencing a lexical |
1366 | variable defined in an outer subroutine. |
1367 | |
1368 | When the inner subroutine is called, it will probably see the value of |
1369 | the outer subroutine's variable as it was before and during the |
1370 | *first* call to the outer subroutine; in this case, after the first |
1371 | call to the outer subroutine is complete, the inner and outer |
1372 | subroutines will no longer share a common value for the variable. In |
1373 | other words, the variable will no longer be shared. |
1374 | |
1375 | Furthermore, if the outer subroutine is anonymous and references a |
1376 | lexical variable outside itself, then the outer and inner subroutines |
1377 | will I<never> share the given variable. |
1378 | |
1379 | This problem can usually be solved by making the inner subroutine |
1380 | anonymous, using the C<sub {}> syntax. When inner anonymous subs that |
1381 | reference variables in outer subroutines are called or referenced, |
54310121 |
1382 | they are automatically rebound to the current values of such |
774d564b |
1383 | variables. |
1384 | |
1385 | =item Warning: something's wrong |
1386 | |
1387 | (W) You passed warn() an empty string (the equivalent of C<warn "">) or |
1388 | you called it with no args and C<$_> was empty. |
1389 | |
54310121 |
1390 | =item Ill-formed logical name |%s| in prime_env_iter |
1391 | |
1392 | (W) A warning peculiar to VMS. A logical name was encountered when preparing |
1393 | to iterate over %ENV which violates the syntactic rules governing logical |
1394 | names. Since it cannot be translated normally, it is skipped, and will not |
1395 | appear in %ENV. This may be a benign occurrence, as some software packages |
1396 | might directly modify logical name tables and introduce nonstandard names, |
1397 | or it may indicate that a logical name table has been corrupted. |
1398 | |
774d564b |
1399 | =item Got an error from DosAllocMem |
5f05dabc |
1400 | |
774d564b |
1401 | (P) An error peculiar to OS/2. Most probably you're using an obsolete |
1402 | version of Perl, and this should not happen anyway. |
5f05dabc |
1403 | |
1404 | =item Malformed PERLLIB_PREFIX |
1405 | |
dc848c6f |
1406 | (F) An error peculiar to OS/2. PERLLIB_PREFIX should be of the form |
5f05dabc |
1407 | |
1408 | prefix1;prefix2 |
1409 | |
1410 | or |
1411 | |
1412 | prefix1 prefix2 |
1413 | |
dc848c6f |
1414 | with nonempty prefix1 and prefix2. If C<prefix1> is indeed a prefix |
1415 | of a builtin library search path, prefix2 is substituted. The error |
1416 | may appear if components are not found, or are too long. See |
1417 | "PERLLIB_PREFIX" in F<README.os2>. |
5f05dabc |
1418 | |
1419 | =item PERL_SH_DIR too long |
1420 | |
1421 | (F) An error peculiar to OS/2. PERL_SH_DIR is the directory to find the |
dc848c6f |
1422 | C<sh>-shell in. See "PERL_SH_DIR" in F<README.os2>. |
5f05dabc |
1423 | |
1424 | =item Process terminated by SIG%s |
1425 | |
1426 | (W) This is a standard message issued by OS/2 applications, while *nix |
dc848c6f |
1427 | applications die in silence. It is considered a feature of the OS/2 |
1428 | port. One can easily disable this by appropriate sighandlers, see |
1429 | L<perlipc/"Signals">. See also "Process terminated by SIGTERM/SIGINT" |
1430 | in F<README.os2>. |
5f05dabc |
1431 | |
1432 | =back |
1433 | |
1434 | =head1 BUGS |
1435 | |
774d564b |
1436 | If you find what you think is a bug, you might check the headers of |
1437 | recently posted articles in the comp.lang.perl.misc newsgroup. |
1438 | There may also be information at http://www.perl.com/perl/, the Perl |
1439 | Home Page. |
5f05dabc |
1440 | |
1441 | If you believe you have an unreported bug, please run the B<perlbug> |
9607fc9c |
1442 | program included with your release. Make sure you trim your bug down |
1443 | to a tiny but sufficient test case. Your bug report, along with the |
1444 | output of C<perl -V>, will be sent off to <F<perlbug@perl.com>> to be |
1445 | analysed by the Perl porting team. |
5f05dabc |
1446 | |
1447 | =head1 SEE ALSO |
1448 | |
1449 | The F<Changes> file for exhaustive details on what changed. |
1450 | |
1451 | The F<INSTALL> file for how to build Perl. This file has been |
1452 | significantly updated for 5.004, so even veteran users should |
1453 | look through it. |
1454 | |
1455 | The F<README> file for general stuff. |
1456 | |
1457 | The F<Copying> file for copyright information. |
1458 | |
1459 | =head1 HISTORY |
1460 | |
1461 | Constructed by Tom Christiansen, grabbing material with permission |
1462 | from innumerable contributors, with kibitzing by more than a few Perl |
1463 | porters. |
1464 | |
2ae324a7 |
1465 | Last update: Sat Mar 8 19:51:26 EST 1997 |