This is a live mirror of the Perl 5 development currently hosted at https://github.com/perl/perl5
Don't explicitly talk about our support for DBM files as a feature.
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1=head1 NAME
2
095a5c3e 3perl - The Perl 5 language interpreter
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4
5=head1 SYNOPSIS
6
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7B<perl> S<[ B<-sTtuUWX> ]>
8 S<[ B<-hv> ] [ B<-V>[:I<configvar>] ]>
9 S<[ B<-cw> ] [ B<-d>[B<t>][:I<debugger>] ] [ B<-D>[I<number/list>] ]>
10 S<[ B<-pna> ] [ B<-F>I<pattern> ] [ B<-l>[I<octal>] ] [ B<-0>[I<octal/hexadecimal>] ]>
11 S<[ B<-I>I<dir> ] [ B<-m>[B<->]I<module> ] [ B<-M>[B<->]I<'module...'> ] [ B<-f> ]>
df451b2a 12 S<[ B<-C [I<number/list>] >]>
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13 S<[ B<-S> ]>
14 S<[ B<-x>[I<dir>] ]>
15 S<[ B<-i>[I<extension>] ]>
eb1dd64e 16 S<[ [B<-e>|B<-E>] I<'command'> ] [ B<--> ] [ I<programfile> ] [ I<argument> ]...>
c07a80fd 17
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18=head1 GETTING HELP
19
20The F<perldoc> program gives you access to all the documentation that comes
21with Perl. You can get more documentation, tutorials and community support
22online at L<http://www.perl.org/>.
23
24If you're new to Perl, you should start by running C<perldoc perlintro>,
25which is a general intro for beginners and provides some background to help
26you navigate the rest of Perl's extensive documentation. Run C<perldoc
27perldoc> to learn more things you can do with F<perldoc>.
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28
29For ease of access, the Perl manual has been split up into several sections.
a0d0e21e 30
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31=head2 Overview
32
fb9cefb4 33 perl Perl overview (this section)
10151d09 34 perlintro Perl introduction for beginners
fb9cefb4 35 perltoc Perl documentation table of contents
760ac839 36
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37=head2 Tutorials
38
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39 perlreftut Perl references short introduction
40 perldsc Perl data structures intro
41 perllol Perl data structures: arrays of arrays
7a2320f0 42
41630250 43 perlrequick Perl regular expressions quick start
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44 perlretut Perl regular expressions tutorial
45
46 perlboot Perl OO tutorial for beginners
47 perltoot Perl OO tutorial, part 1
48 perltooc Perl OO tutorial, part 2
49 perlbot Perl OO tricks and examples
50
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51 perlperf Perl Performance and Optimization Techniques
52
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53 perlstyle Perl style guide
54
41630250 55 perlcheat Perl cheat sheet
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56 perltrap Perl traps for the unwary
57 perldebtut Perl debugging tutorial
58
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59 perlfaq Perl frequently asked questions
60 perlfaq1 General Questions About Perl
61 perlfaq2 Obtaining and Learning about Perl
62 perlfaq3 Programming Tools
63 perlfaq4 Data Manipulation
64 perlfaq5 Files and Formats
65 perlfaq6 Regexes
66 perlfaq7 Perl Language Issues
67 perlfaq8 System Interaction
68 perlfaq9 Networking
0f542199 69
fd7b6849 70=head2 Reference Manual
413510b3 71
fb9cefb4 72 perlsyn Perl syntax
4755096e 73 perldata Perl data structures
fb9cefb4 74 perlop Perl operators and precedence
c2e66d9e 75 perlsub Perl subroutines
fd7b6849 76 perlfunc Perl built-in functions
413510b3 77 perlopentut Perl open() tutorial
41630250 78 perlpacktut Perl pack() and unpack() tutorial
c2e66d9e 79 perlpod Perl plain old documentation
41630250 80 perlpodspec Perl plain old documentation format specification
f4d47668 81 perlpodstyle Perl POD style guide
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82 perlrun Perl execution and options
83 perldiag Perl diagnostic messages
41630250 84 perllexwarn Perl warnings and their control
4755096e 85 perldebug Perl debugging
fb9cefb4 86 perlvar Perl predefined variables
4755096e 87 perlre Perl regular expressions, the rest of the story
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88 perlrebackslash Perl regular expression backslash sequences
89 perlrecharclass Perl regular expression character classes
30487ceb 90 perlreref Perl regular expressions quick reference
d396a558 91 perlref Perl references, the rest of the story
fb9cefb4 92 perlform Perl formats
d396a558 93 perlobj Perl objects
d396a558 94 perltie Perl objects hidden behind simple variables
fd7b6849 95 perldbmfilter Perl DBM filters
760ac839 96
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97 perlipc Perl interprocess communication
98 perlfork Perl fork() information
99 perlnumber Perl number semantics
53d7eaa8 100
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101 perlthrtut Perl threads tutorial
102
103 perlport Perl portability guide
d396a558 104 perllocale Perl locale support
07fcf8ff 105 perluniintro Perl Unicode introduction
41630250 106 perlunicode Perl Unicode support
3426ea3d 107 perlunifaq Perl Unicode FAQ
ba634883 108 perluniprops Index of Unicode Version 6.0.0 properties in Perl
aadaa455 109 perlunitut Perl Unicode tutorial
d396a558 110 perlebcdic Considerations for running Perl on EBCDIC platforms
c2e66d9e 111
d396a558 112 perlsec Perl security
4755096e 113
c2e66d9e 114 perlmod Perl modules: how they work
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115 perlmodlib Perl modules: how to write and use
116 perlmodstyle Perl modules: how to write modules with style
fd7b6849 117 perlmodinstall Perl modules: how to install from CPAN
c2e66d9e 118 perlnewmod Perl modules: preparing a new module for distribution
a550ee30 119 perlpragma Perl modules: writing a user pragma
760ac839 120
fd7b6849 121 perlutil utilities packaged with the Perl distribution
760ac839 122
41630250 123 perlcompile Perl compiler suite intro
760ac839 124
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125 perlfilter Perl source filters
126
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127 perlglossary Perl Glossary
128
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129=head2 Internals and C Language Interface
130
fb9cefb4 131 perlembed Perl ways to embed perl in your C or C++ application
41630250 132 perldebguts Perl debugging guts and tips
fb9cefb4 133 perlxstut Perl XS tutorial
4755096e 134 perlxs Perl XS application programming interface
f40a6c71 135 perlclib Internal replacements for standard C library functions
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136 perlguts Perl internal functions for those doing extensions
137 perlcall Perl calling conventions from C
15932acc 138 perlmroapi Perl method resolution plugin interface
108003db 139 perlreapi Perl regular expression plugin interface
b23a565d 140 perlreguts Perl regular expression engine internals
fd7b6849 141
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142 perlapi Perl API listing (autogenerated)
143 perlintern Perl internal functions (autogenerated)
dc5c060f 144 perliol C API for Perl's implementation of IO in Layers
4755096e 145 perlapio Perl internal IO abstraction interface
fd7b6849 146
e8cd7eae 147 perlhack Perl hackers guide
cb8a010e 148 perlpolicy Perl development policies
00f54a07 149 perlrepository Perl source repository
4755096e 150
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151=head2 Miscellaneous
152
153 perlbook Perl book information
cbd87e7e 154 perlcommunity Perl community information
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155 perltodo Perl things to do
156
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157 perldoc Look up Perl documentation in Pod format
158
fb9cefb4 159 perlhist Perl history records
bdfb6cc8 160 perldelta Perl changes since previous version
ba634883 161 perl5137delta Perl changes in version 5.13.7
f4d47668 162 perl5136delta Perl changes in version 5.13.6
ee0887a9 163 perl5135delta Perl changes in version 5.13.5
587354ab 164 perl5134delta Perl changes in version 5.13.4
cea2f1cb 165 perl5133delta Perl changes in version 5.13.3
855e1b21 166 perl5132delta Perl changes in version 5.13.2
f83c51e5 167 perl5131delta Perl changes in version 5.13.1
d4438f94 168 perl5130delta Perl changes in version 5.13.0
e71d1a7d 169 perl5122delta Perl changes in version 5.12.2
bdfb6cc8 170 perl5121delta Perl changes in version 5.12.1
20d57231 171 perl5120delta Perl changes in version 5.12.0
655da5cf 172 perl5115delta Perl changes in version 5.11.5
3be84f1f 173 perl5114delta Perl changes in version 5.11.4
e06a4ec4 174 perl5113delta Perl changes in version 5.11.3
2e8102e6 175 perl5112delta Perl changes in version 5.11.2
d5114285 176 perl5111delta Perl changes in version 5.11.1
11545435 177 perl5110delta Perl changes in version 5.11.0
7cdf958d 178 perl5101delta Perl changes in version 5.10.1
7120b314 179 perl5100delta Perl changes in version 5.10.0
cf6c151c 180 perl595delta Perl changes in version 5.9.5
f6eae373 181 perl594delta Perl changes in version 5.9.4
6c7deadb 182 perl593delta Perl changes in version 5.9.3
496c75d0 183 perl592delta Perl changes in version 5.9.2
e0eb806d 184 perl591delta Perl changes in version 5.9.1
1400179b 185 perl590delta Perl changes in version 5.9.0
fc5be808 186 perl589delta Perl changes in version 5.8.9
c11a53c6 187 perl588delta Perl changes in version 5.8.8
315ba985 188 perl587delta Perl changes in version 5.8.7
e4bb216d 189 perl586delta Perl changes in version 5.8.6
07e9b5fe 190 perl585delta Perl changes in version 5.8.5
5f15c94e 191 perl584delta Perl changes in version 5.8.4
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192 perl583delta Perl changes in version 5.8.3
193 perl582delta Perl changes in version 5.8.2
b6235c4f 194 perl581delta Perl changes in version 5.8.1
2e038148 195 perl58delta Perl changes in version 5.8.0
77b096b5 196 perl573delta Perl changes in version 5.7.3
245d750e 197 perl572delta Perl changes in version 5.7.2
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198 perl571delta Perl changes in version 5.7.1
199 perl570delta Perl changes in version 5.7.0
493a87da 200 perl561delta Perl changes in version 5.6.1
41630250 201 perl56delta Perl changes in version 5.6
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202 perl5005delta Perl changes in version 5.005
203 perl5004delta Perl changes in version 5.004
d516a115 204
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205 perlartistic Perl Artistic License
206 perlgpl GNU General Public License
207
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208=head2 Language-Specific
209
210 perlcn Perl for Simplified Chinese (in EUC-CN)
211 perljp Perl for Japanese (in EUC-JP)
212 perlko Perl for Korean (in EUC-KR)
213 perltw Perl for Traditional Chinese (in Big5)
214
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215=head2 Platform-Specific
216
37d4d706 217 perlaix Perl notes for AIX
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218 perlamiga Perl notes for AmigaOS
219 perlapollo Perl notes for Apollo DomainOS
220 perlbeos Perl notes for BeOS
dc5c060f 221 perlbs2000 Perl notes for POSIX-BC BS2000
a1f19229 222 perlce Perl notes for WinCE
49877630 223 perlcygwin Perl notes for Cygwin
245d750e 224 perldgux Perl notes for DG/UX
49877630 225 perldos Perl notes for DOS
9a997319 226 perlepoc Perl notes for EPOC
41630250 227 perlfreebsd Perl notes for FreeBSD
f6706af3 228 perlhaiku Perl notes for Haiku
49877630 229 perlhpux Perl notes for HP-UX
a83b6f46 230 perlhurd Perl notes for Hurd
469e7be4 231 perlirix Perl notes for Irix
991e8403 232 perllinux Perl notes for Linux
26d9b02f 233 perlmacos Perl notes for Mac OS (Classic)
0d53b15f 234 perlmacosx Perl notes for Mac OS X
ab648d5e 235 perlmpeix Perl notes for MPE/iX
41630250 236 perlnetware Perl notes for NetWare
b0846812 237 perlopenbsd Perl notes for OpenBSD
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238 perlos2 Perl notes for OS/2
239 perlos390 Perl notes for OS/390
522b859a 240 perlos400 Perl notes for OS/400
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241 perlplan9 Perl notes for Plan 9
242 perlqnx Perl notes for QNX
2f08ed66 243 perlriscos Perl notes for RISC OS
d420ca49 244 perlsolaris Perl notes for Solaris
27da23d5 245 perlsymbian Perl notes for Symbian
772ff3b9 246 perltru64 Perl notes for Tru64
41630250 247 perluts Perl notes for UTS
cbe1151c 248 perlvmesa Perl notes for VM/ESA
49877630 249 perlvms Perl notes for VMS
9a997319 250 perlvos Perl notes for Stratus VOS
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251 perlwin32 Perl notes for Windows
252
35dec5db 253
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254On a Unix-like system, these documentation files will usually also be
255available as manpages for use with the F<man> program.
a0d0e21e 256
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257In general, if something strange has gone wrong with your program and you're
258not sure where you should look for help, try the B<-w> switch first. It will
259often point out exactly where the trouble is.
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260
261=head1 DESCRIPTION
262
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263Perl officially stands for Practical Extraction and Report Language,
264except when it doesn't.
265
5f05dabc 266Perl is a language optimized for scanning arbitrary
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267text files, extracting information from those text files, and printing
268reports based on that information. It's also a good language for many
269system management tasks. The language is intended to be practical
270(easy to use, efficient, complete) rather than beautiful (tiny,
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271elegant, minimal).
272
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273Perl combines (in the author's opinion, anyway) some of the best
274features of C, B<sed>, B<awk>, and B<sh>, so people familiar with
275those languages should have little difficulty with it. (Language
276historians will also note some vestiges of B<csh>, Pascal, and even
14218588 277BASIC-PLUS.) Expression syntax corresponds closely to C
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278expression syntax. Unlike most Unix utilities, Perl does not
279arbitrarily limit the size of your data--if you've got the memory,
aa689395 280Perl can slurp in your whole file as a single string. Recursion is of
0f31cffe 281unlimited depth. And the tables used by hashes (sometimes called
aa689395 282"associative arrays") grow as necessary to prevent degraded
0f31cffe 283performance. Perl can use sophisticated pattern matching techniques to
14218588 284scan large amounts of data quickly. Although optimized for
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285scanning text, Perl also has many excellent tools for slicing
286and dicing binary data.
aa689395 287
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288But wait, there's more...
289
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290Begun in 1993 (see L<perlhist>), Perl version 5 is nearly a complete
291rewrite that provides the following additional benefits:
a0d0e21e 292
13a2d996 293=over 4
a0d0e21e 294
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295=item *
296
297modularity and reusability using innumerable modules
a0d0e21e 298
19799a22 299Described in L<perlmod>, L<perlmodlib>, and L<perlmodinstall>.
a0d0e21e 300
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301=item *
302
303embeddable and extensible
a0d0e21e 304
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305Described in L<perlembed>, L<perlxstut>, L<perlxs>, L<perlcall>,
306L<perlguts>, and L<xsubpp>.
a0d0e21e 307
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308=item *
309
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310roll-your-own magic variables (including multiple simultaneous DBM
311implementations)
a0d0e21e 312
19799a22 313Described in L<perltie> and L<AnyDBM_File>.
a0d0e21e 314
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315=item *
316
317subroutines can now be overridden, autoloaded, and prototyped
a0d0e21e 318
19799a22 319Described in L<perlsub>.
a0d0e21e 320
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321=item *
322
323arbitrarily nested data structures and anonymous functions
a0d0e21e 324
19799a22 325Described in L<perlreftut>, L<perlref>, L<perldsc>, and L<perllol>.
a0d0e21e 326
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327=item *
328
329object-oriented programming
a0d0e21e 330
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331Described in L<perlobj>, L<perlboot>, L<perltoot>, L<perltooc>,
332and L<perlbot>.
a0d0e21e 333
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334=item *
335
551e1d92 336support for light-weight processes (threads)
a0d0e21e 337
63de3cb2 338Described in L<perlthrtut> and L<threads>.
a0d0e21e 339
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340=item *
341
63de3cb2 342support for Unicode, internationalization, and localization
a0d0e21e 343
63de3cb2 344Described in L<perluniintro>, L<perllocale> and L<Locale::Maketext>.
a0d0e21e 345
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346=item *
347
348lexical scoping
a0d0e21e 349
19799a22 350Described in L<perlsub>.
a0d0e21e 351
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352=item *
353
354regular expression enhancements
a0d0e21e 355
19799a22 356Described in L<perlre>, with additional examples in L<perlop>.
a0d0e21e 357
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358=item *
359
360enhanced debugger and interactive Perl environment,
361with integrated editor support
a0d0e21e 362
f6b3c421 363Described in L<perldebtut>, L<perldebug> and L<perldebguts>.
a0d0e21e 364
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365=item *
366
367POSIX 1003.1 compliant library
5f05dabc 368
19799a22 369Described in L<POSIX>.
5f05dabc 370
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371=back
372
68dc0745 373Okay, that's I<definitely> enough hype.
a0d0e21e 374
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375=head1 AVAILABILITY
376
14218588 377Perl is available for most operating systems, including virtually
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378all Unix-like platforms. See L<perlport/"Supported Platforms">
379for a listing.
8bc4a6bb 380
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381=head1 ENVIRONMENT
382
1e422769 383See L<perlrun>.
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384
385=head1 AUTHOR
386
19799a22 387Larry Wall <larry@wall.org>, with the help of oodles of other folks.
a0d0e21e 388
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389If your Perl success stories and testimonials may be of help to others
390who wish to advocate the use of Perl in their applications,
391or if you wish to simply express your gratitude to Larry and the
19799a22 392Perl developers, please write to perl-thanks@perl.org .
a99b1639 393
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394=head1 FILES
395
5f05dabc 396 "@INC" locations of perl libraries
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397
398=head1 SEE ALSO
399
c5f69108 400 http://www.perl.org/ the Perl homepage
da9e6348 401 http://www.perl.com/ Perl articles (O'Reilly)
f6b3c421 402 http://www.cpan.org/ the Comprehensive Perl Archive
c5f69108 403 http://www.pm.org/ the Perl Mongers
19799a22 404
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405=head1 DIAGNOSTICS
406
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407The C<use warnings> pragma (and the B<-w> switch) produces some
408lovely diagnostics.
a0d0e21e 409
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410See L<perldiag> for explanations of all Perl's diagnostics. The C<use
411diagnostics> pragma automatically turns Perl's normally terse warnings
412and errors into these longer forms.
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413
414Compilation errors will tell you the line number of the error, with an
415indication of the next token or token type that was to be examined.
14218588 416(In a script passed to Perl via B<-e> switches, each
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417B<-e> is counted as one line.)
418
419Setuid scripts have additional constraints that can produce error
420messages such as "Insecure dependency". See L<perlsec>.
421
422Did we mention that you should definitely consider using the B<-w>
423switch?
424
425=head1 BUGS
426
427The B<-w> switch is not mandatory.
428
429Perl is at the mercy of your machine's definitions of various
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430operations such as type casting, atof(), and floating-point
431output with sprintf().
a0d0e21e 432
748a9306 433If your stdio requires a seek or eof between reads and writes on a
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434particular stream, so does Perl. (This doesn't apply to sysread()
435and syswrite().)
436
437While none of the built-in data types have any arbitrary size limits
438(apart from memory size), there are still a few arbitrary limits: a
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439given variable name may not be longer than 251 characters. Line numbers
440displayed by diagnostics are internally stored as short integers,
441so they are limited to a maximum of 65535 (higher numbers usually being
442affected by wraparound).
a0d0e21e 443
b0607b7a 444You may mail your bug reports (be sure to include full configuration
19799a22 445information as output by the myconfig program in the perl source
7f2de2d2 446tree, or by C<perl -V>) to perlbug@perl.org . If you've succeeded
7f89f796 447in compiling perl, the L<perlbug> script in the F<utils/> subdirectory
19799a22 448can be used to help mail in a bug report.
4633a7c4 449
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450Perl actually stands for Pathologically Eclectic Rubbish Lister, but
451don't tell anyone I said that.
452
453=head1 NOTES
454
455The Perl motto is "There's more than one way to do it." Divining
456how many more is left as an exercise to the reader.
457
4633a7c4 458The three principal virtues of a programmer are Laziness,
a0d0e21e 459Impatience, and Hubris. See the Camel Book for why.
16d20bd9 460