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1 | =head1 NAME |
2 | |
3 | perl - Practical Extraction and Report Language |
4 | |
5 | =head1 SYNOPSIS |
6 | |
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7 | B<perl> S<[ B<-sTuU> ]> |
8 | S<[ B<-hv> ] [ B<-V>[:I<configvar>] ]> |
9 | S<[ B<-cw> ] [ B<-d>[:I<debugger>] ] [ B<-D>[I<number/list>] ]> |
10 | S<[ B<-pna> ] [ B<-F>I<pattern> ] [ B<-l>[I<octal>] ] [ B<-0>[I<octal>] ]> |
11 | S<[ B<-I>I<dir> ] [ B<-m>[B<->]I<module> ] [ B<-M>[B<->]I<'module...'> ]> |
12 | S<[ B<-P> ]> |
13 | S<[ B<-S> ]> |
14 | S<[ B<-x>[I<dir>] ]> |
15 | S<[ B<-i>[I<extension>] ]> |
16 | S<[ B<-e> I<'command'> ] [ B<--> ] [ I<programfile> ] [ I<argument> ]...> |
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17 | |
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18 | For ease of access, the Perl manual has been split up into a number |
19 | of sections: |
20 | |
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21 | perl Perl overview (this section) |
22 | perldelta Perl changes since previous version |
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23 | perl5005delta Perl changes in version 5.005 |
24 | perl5004delta Perl changes in version 5.004 |
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25 | perlfaq Perl frequently asked questions |
26 | perltoc Perl documentation table of contents |
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27 | |
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28 | perldata Perl data structures |
29 | perlsyn Perl syntax |
30 | perlop Perl operators and precedence |
31 | perlre Perl regular expressions |
32 | perlrun Perl execution and options |
33 | perlfunc Perl builtin functions |
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34 | perlopentut Perl open() tutorial |
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35 | perlvar Perl predefined variables |
36 | perlsub Perl subroutines |
37 | perlmod Perl modules: how they work |
38 | perlmodlib Perl modules: how to write and use |
39 | perlmodinstall Perl modules: how to install from CPAN |
40 | perlform Perl formats |
41 | perllocale Perl locale support |
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42 | |
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43 | perlref Perl references |
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44 | perlreftut Perl references short introduction |
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45 | perldsc Perl data structures intro |
46 | perllol Perl data structures: lists of lists |
47 | perltoot Perl OO tutorial |
48 | perlobj Perl objects |
49 | perltie Perl objects hidden behind simple variables |
50 | perlbot Perl OO tricks and examples |
51 | perlipc Perl interprocess communication |
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52 | perlthrtut Perl threads tutorial |
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53 | |
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54 | perldebug Perl debugging |
55 | perldiag Perl diagnostic messages |
56 | perlsec Perl security |
57 | perltrap Perl traps for the unwary |
58 | perlport Perl portability guide |
59 | perlstyle Perl style guide |
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60 | |
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61 | perlpod Perl plain old documentation |
62 | perlbook Perl book information |
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63 | |
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64 | perlembed Perl ways to embed perl in your C or C++ application |
65 | perlapio Perl internal IO abstraction interface |
66 | perlxs Perl XS application programming interface |
67 | perlxstut Perl XS tutorial |
68 | perlguts Perl internal functions for those doing extensions |
69 | perlcall Perl calling conventions from C |
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70 | |
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71 | perltodo Perl things to do |
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72 | perlhist Perl history records |
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73 | |
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74 | (If you're intending to read these straight through for the first time, |
75 | the suggested order will tend to reduce the number of forward references.) |
76 | |
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77 | By default, all of the above manpages are installed in the |
78 | F</usr/local/man/> directory. |
79 | |
80 | Extensive additional documentation for Perl modules is available. The |
81 | default configuration for perl will place this additional documentation |
82 | in the F</usr/local/lib/perl5/man> directory (or else in the F<man> |
83 | subdirectory of the Perl library directory). Some of this additional |
84 | documentation is distributed standard with Perl, but you'll also find |
85 | documentation for third-party modules there. |
86 | |
87 | You should be able to view Perl's documentation with your man(1) |
88 | program by including the proper directories in the appropriate start-up |
89 | files, or in the MANPATH environment variable. To find out where the |
90 | configuration has installed the manpages, type: |
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91 | |
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92 | perl -V:man.dir |
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93 | |
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94 | If the directories have a common stem, such as F</usr/local/man/man1> |
95 | and F</usr/local/man/man3>, you need only to add that stem |
96 | (F</usr/local/man>) to your man(1) configuration files or your MANPATH |
97 | environment variable. If they do not share a stem, you'll have to add |
98 | both stems. |
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99 | |
100 | If that doesn't work for some reason, you can still use the |
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101 | supplied F<perldoc> script to view module information. You might |
102 | also look into getting a replacement man program. |
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103 | |
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104 | If something strange has gone wrong with your program and you're not |
105 | sure where you should look for help, try the B<-w> switch first. It |
106 | will often point out exactly where the trouble is. |
107 | |
108 | =head1 DESCRIPTION |
109 | |
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110 | Perl is a language optimized for scanning arbitrary |
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111 | text files, extracting information from those text files, and printing |
112 | reports based on that information. It's also a good language for many |
113 | system management tasks. The language is intended to be practical |
114 | (easy to use, efficient, complete) rather than beautiful (tiny, |
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115 | elegant, minimal). |
116 | |
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117 | Perl combines (in the author's opinion, anyway) some of the best |
118 | features of C, B<sed>, B<awk>, and B<sh>, so people familiar with |
119 | those languages should have little difficulty with it. (Language |
120 | historians will also note some vestiges of B<csh>, Pascal, and even |
121 | BASIC-PLUS.) Expression syntax corresponds quite closely to C |
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122 | expression syntax. Unlike most Unix utilities, Perl does not |
123 | arbitrarily limit the size of your data--if you've got the memory, |
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124 | Perl can slurp in your whole file as a single string. Recursion is of |
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125 | unlimited depth. And the tables used by hashes (sometimes called |
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126 | "associative arrays") grow as necessary to prevent degraded |
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127 | performance. Perl can use sophisticated pattern matching techniques to |
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128 | scan large amounts of data very quickly. Although optimized for |
129 | scanning text, Perl can also deal with binary data, and can make dbm |
130 | files look like hashes. Setuid Perl scripts are safer than C programs |
131 | through a dataflow tracing mechanism which prevents many stupid |
132 | security holes. |
133 | |
134 | If you have a problem that would ordinarily use B<sed> or B<awk> or |
135 | B<sh>, but it exceeds their capabilities or must run a little faster, |
136 | and you don't want to write the silly thing in C, then Perl may be for |
137 | you. There are also translators to turn your B<sed> and B<awk> |
138 | scripts into Perl scripts. |
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139 | |
140 | But wait, there's more... |
141 | |
142 | Perl version 5 is nearly a complete rewrite, and provides |
143 | the following additional benefits: |
144 | |
145 | =over 5 |
146 | |
147 | =item * Many usability enhancements |
148 | |
149 | It is now possible to write much more readable Perl code (even within |
150 | regular expressions). Formerly cryptic variable names can be replaced |
151 | by mnemonic identifiers. Error messages are more informative, and the |
152 | optional warnings will catch many of the mistakes a novice might make. |
153 | This cannot be stressed enough. Whenever you get mysterious behavior, |
154 | try the B<-w> switch!!! Whenever you don't get mysterious behavior, |
155 | try using B<-w> anyway. |
156 | |
157 | =item * Simplified grammar |
158 | |
159 | The new yacc grammar is one half the size of the old one. Many of the |
160 | arbitrary grammar rules have been regularized. The number of reserved |
161 | words has been cut by 2/3. Despite this, nearly all old Perl scripts |
162 | will continue to work unchanged. |
163 | |
164 | =item * Lexical scoping |
165 | |
166 | Perl variables may now be declared within a lexical scope, like "auto" |
167 | variables in C. Not only is this more efficient, but it contributes |
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168 | to better privacy for "programming in the large". Anonymous |
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169 | subroutines exhibit deep binding of lexical variables (closures). |
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170 | |
171 | =item * Arbitrarily nested data structures |
172 | |
173 | Any scalar value, including any array element, may now contain a |
174 | reference to any other variable or subroutine. You can easily create |
175 | anonymous variables and subroutines. Perl manages your reference |
176 | counts for you. |
177 | |
178 | =item * Modularity and reusability |
179 | |
180 | The Perl library is now defined in terms of modules which can be easily |
181 | shared among various packages. A package may choose to import all or a |
182 | portion of a module's published interface. Pragmas (that is, compiler |
183 | directives) are defined and used by the same mechanism. |
184 | |
185 | =item * Object-oriented programming |
186 | |
187 | A package can function as a class. Dynamic multiple inheritance and |
188 | virtual methods are supported in a straightforward manner and with very |
189 | little new syntax. Filehandles may now be treated as objects. |
190 | |
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191 | =item * Embeddable and Extensible |
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192 | |
193 | Perl may now be embedded easily in your C or C++ application, and can |
194 | either call or be called by your routines through a documented |
195 | interface. The XS preprocessor is provided to make it easy to glue |
196 | your C or C++ routines into Perl. Dynamic loading of modules is |
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197 | supported, and Perl itself can be made into a dynamic library. |
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198 | |
199 | =item * POSIX compliant |
200 | |
201 | A major new module is the POSIX module, which provides access to all |
202 | available POSIX routines and definitions, via object classes where |
203 | appropriate. |
204 | |
205 | =item * Package constructors and destructors |
206 | |
207 | The new BEGIN and END blocks provide means to capture control as |
208 | a package is being compiled, and after the program exits. As a |
209 | degenerate case they work just like awk's BEGIN and END when you |
210 | use the B<-p> or B<-n> switches. |
211 | |
212 | =item * Multiple simultaneous DBM implementations |
213 | |
214 | A Perl program may now access DBM, NDBM, SDBM, GDBM, and Berkeley DB |
215 | files from the same script simultaneously. In fact, the old dbmopen |
216 | interface has been generalized to allow any variable to be tied |
217 | to an object class which defines its access methods. |
218 | |
219 | =item * Subroutine definitions may now be autoloaded |
220 | |
221 | In fact, the AUTOLOAD mechanism also allows you to define any arbitrary |
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222 | semantics for undefined subroutine calls. It's not for just autoloading. |
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223 | |
224 | =item * Regular expression enhancements |
225 | |
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226 | You can now specify nongreedy quantifiers. You can now do grouping |
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227 | without creating a backreference. You can now write regular expressions |
228 | with embedded whitespace and comments for readability. A consistent |
229 | extensibility mechanism has been added that is upwardly compatible with |
230 | all old regular expressions. |
231 | |
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232 | =item * Innumerable Unbundled Modules |
233 | |
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234 | The Comprehensive Perl Archive Network described in L<perlmodlib> |
235 | contains hundreds of plug-and-play modules full of reusable code. |
236 | See F<http://www.perl.com/CPAN> for a site near you. |
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237 | |
238 | =item * Compilability |
239 | |
240 | While not yet in full production mode, a working perl-to-C compiler |
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241 | does exist. It can generate portable byte code, simple C, or |
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242 | optimized C code. |
243 | |
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244 | =back |
245 | |
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246 | Okay, that's I<definitely> enough hype. |
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247 | |
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248 | =head1 AVAILABILITY |
249 | |
250 | Perl is available for the vast majority of operating system platforms, |
251 | including most Unix-like platforms. The following situation is as of |
252 | February 1999 and Perl 5.005_03. |
253 | |
254 | The following platforms are able to build Perl from the standard |
255 | source code distribution available at |
256 | F<http://www.perl.com/CPAN/src/index.html> |
257 | |
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258 | AIX Linux SCO ODT/OSR |
259 | A/UX MachTen Solaris |
260 | BeOS MPE/iX SunOS |
261 | BSD/OS NetBSD SVR4 |
262 | DG/UX NextSTEP Tru64 UNIX 3) |
263 | DomainOS OpenBSD Ultrix |
264 | DOS DJGPP 1) OpenSTEP UNICOS |
265 | DYNIX/ptx OS/2 VMS |
266 | FreeBSD OS390 2) VOS |
267 | HP-UX PowerMAX Windows 3.1 1) |
268 | Hurd QNX Windows 95 1) 4) |
269 | IRIX Windows 98 1) 4) |
270 | Windows NT 1) 4) |
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271 | |
272 | 1) in DOS mode either the DOS or OS/2 ports can be used |
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273 | 2) formerly known as MVS |
274 | 3) formerly known as Digital UNIX and before that DEC OSF/1 |
275 | 4) compilers: Borland, Cygwin32, Mingw32 EGCS/GCC, VC++ |
276 | |
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277 | The following platforms have been known to build Perl from the source |
278 | but for the Perl release 5.005_03 we haven't been able to verify them, |
279 | either because the hardware/software platforms are rather rare or |
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280 | because we don't have an active champion on these platforms, or both. |
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281 | |
282 | 3b1 FPS Plan 9 |
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283 | AmigaOS GENIX PowerUX |
284 | ConvexOS Greenhills RISC/os |
285 | CX/UX ISC Stellar |
286 | DC/OSx MachTen 68k SVR2 |
287 | DDE SMES MiNT TI1500 |
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288 | DOS EMX MPC TitanOS |
289 | Dynix NEWS-OS UNICOS/mk |
290 | EP/IX Opus Unisys Dynix |
291 | ESIX Unixware |
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292 | |
293 | The following platforms are planned to be supported in the standard |
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294 | source code distribution of the Perl release 5.006 but are not |
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295 | supported in the Perl release 5.005_03: |
296 | |
297 | BS2000 |
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298 | Netware |
299 | Rhapsody |
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300 | VM/ESA |
301 | |
302 | The following platforms have their own source code distributions and |
303 | binaries available via F<http://www.perl.com/CPAN/ports/index.html>. |
304 | |
305 | Perl release |
306 | |
307 | AS/400 5.003 |
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308 | MacOS 5.004 |
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309 | Netware 5.003_07 |
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310 | Tandem Guardian 5.004 |
311 | |
312 | The following platforms have only binaries available via |
313 | F<http://www.perl.com/CPAN/ports/index.html>. |
314 | |
315 | Perl release |
316 | |
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317 | Acorn RISCOS 5.005_02 |
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318 | AOS 5.002 |
319 | LynxOS 5.004_02 |
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320 | |
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321 | =head1 ENVIRONMENT |
322 | |
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323 | See L<perlrun>. |
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324 | |
325 | =head1 AUTHOR |
326 | |
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327 | Larry Wall <F<larry@wall.org>>, with the help of oodles of other folks. |
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328 | |
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329 | If your Perl success stories and testimonials may be of help to others |
330 | who wish to advocate the use of Perl in their applications, |
331 | or if you wish to simply express your gratitude to Larry and the |
332 | Perl developers, please write to <F<perl-thanks@perl.org>>. |
333 | |
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334 | =head1 FILES |
335 | |
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336 | "@INC" locations of perl libraries |
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337 | |
338 | =head1 SEE ALSO |
339 | |
340 | a2p awk to perl translator |
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341 | |
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342 | s2p sed to perl translator |
343 | |
344 | =head1 DIAGNOSTICS |
345 | |
346 | The B<-w> switch produces some lovely diagnostics. |
347 | |
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348 | See L<perldiag> for explanations of all Perl's diagnostics. The C<use |
349 | diagnostics> pragma automatically turns Perl's normally terse warnings |
350 | and errors into these longer forms. |
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351 | |
352 | Compilation errors will tell you the line number of the error, with an |
353 | indication of the next token or token type that was to be examined. |
354 | (In the case of a script passed to Perl via B<-e> switches, each |
355 | B<-e> is counted as one line.) |
356 | |
357 | Setuid scripts have additional constraints that can produce error |
358 | messages such as "Insecure dependency". See L<perlsec>. |
359 | |
360 | Did we mention that you should definitely consider using the B<-w> |
361 | switch? |
362 | |
363 | =head1 BUGS |
364 | |
365 | The B<-w> switch is not mandatory. |
366 | |
367 | Perl is at the mercy of your machine's definitions of various |
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368 | operations such as type casting, atof(), and floating-point |
369 | output with sprintf(). |
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370 | |
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371 | If your stdio requires a seek or eof between reads and writes on a |
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372 | particular stream, so does Perl. (This doesn't apply to sysread() |
373 | and syswrite().) |
374 | |
375 | While none of the built-in data types have any arbitrary size limits |
376 | (apart from memory size), there are still a few arbitrary limits: a |
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377 | given variable name may not be longer than 251 characters. Line numbers |
378 | displayed by diagnostics are internally stored as short integers, |
379 | so they are limited to a maximum of 65535 (higher numbers usually being |
380 | affected by wraparound). |
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381 | |
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382 | You may mail your bug reports (be sure to include full configuration |
383 | information as output by the myconfig program in the perl source tree, |
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384 | or by C<perl -V>) to <F<perlbug@perl.com>>. |
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385 | If you've succeeded in compiling perl, the perlbug script in the utils/ |
386 | subdirectory can be used to help mail in a bug report. |
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387 | |
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388 | Perl actually stands for Pathologically Eclectic Rubbish Lister, but |
389 | don't tell anyone I said that. |
390 | |
391 | =head1 NOTES |
392 | |
393 | The Perl motto is "There's more than one way to do it." Divining |
394 | how many more is left as an exercise to the reader. |
395 | |
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396 | The three principal virtues of a programmer are Laziness, |
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397 | Impatience, and Hubris. See the Camel Book for why. |
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398 | |