This is a live mirror of the Perl 5 development currently hosted at https://github.com/perl/perl5
Fix the phrasing of the previous patch.
[perl5.git] / pod / perl.pod
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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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18For more information on these options, you can run C<perldoc perlrun>.
19
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20=head1 GETTING HELP
21
22The F<perldoc> program gives you access to all the documentation that comes
23with Perl. You can get more documentation, tutorials and community support
24online at L<http://www.perl.org/>.
25
26If you're new to Perl, you should start by running C<perldoc perlintro>,
27which is a general intro for beginners and provides some background to help
28you navigate the rest of Perl's extensive documentation. Run C<perldoc
29perldoc> to learn more things you can do with F<perldoc>.
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30
31For ease of access, the Perl manual has been split up into several sections.
a0d0e21e 32
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33=begin buildtoc
34
35# This section is parsed by Porting/pod_lib.pl for use by pod/buildtoc etc
36
37flag =g perluniprops perlmodlib perlapi perlintern
38flag =go perltoc
39flag =ro perlcn perljp perlko perltw
40flag = perlvms
41
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42path perlfaq.* cpan/perlfaq/lib/
43path perlglossary cpan/perlfaq/lib/
44path perlxs(?:tut|typemap)? dist/ExtUtils-ParseXS/lib/
45path perldoc cpan/Pod-Perldoc/lib/
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46
47aux a2p c2ph h2ph h2xs perlbug pl2pm pod2html pod2man s2p splain xsubpp
48
49=end buildtoc
50
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51=head2 Overview
52
fb9cefb4 53 perl Perl overview (this section)
10151d09 54 perlintro Perl introduction for beginners
b28fe7ca 55 perlrun Perl execution and options
fb9cefb4 56 perltoc Perl documentation table of contents
760ac839 57
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58=head2 Tutorials
59
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60 perlreftut Perl references short introduction
61 perldsc Perl data structures intro
62 perllol Perl data structures: arrays of arrays
7a2320f0 63
41630250 64 perlrequick Perl regular expressions quick start
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65 perlretut Perl regular expressions tutorial
66
82e1c0d9 67 perlootut Perl OO tutorial for beginners
7a2320f0 68
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69 perlperf Perl Performance and Optimization Techniques
70
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71 perlstyle Perl style guide
72
41630250 73 perlcheat Perl cheat sheet
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74 perltrap Perl traps for the unwary
75 perldebtut Perl debugging tutorial
76
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77 perlfaq Perl frequently asked questions
78 perlfaq1 General Questions About Perl
79 perlfaq2 Obtaining and Learning about Perl
80 perlfaq3 Programming Tools
81 perlfaq4 Data Manipulation
82 perlfaq5 Files and Formats
83 perlfaq6 Regexes
84 perlfaq7 Perl Language Issues
85 perlfaq8 System Interaction
86 perlfaq9 Networking
0f542199 87
fd7b6849 88=head2 Reference Manual
413510b3 89
fb9cefb4 90 perlsyn Perl syntax
4755096e 91 perldata Perl data structures
fb9cefb4 92 perlop Perl operators and precedence
c2e66d9e 93 perlsub Perl subroutines
fd7b6849 94 perlfunc Perl built-in functions
413510b3 95 perlopentut Perl open() tutorial
41630250 96 perlpacktut Perl pack() and unpack() tutorial
c2e66d9e 97 perlpod Perl plain old documentation
41630250 98 perlpodspec Perl plain old documentation format specification
f4d47668 99 perlpodstyle Perl POD style guide
c2e66d9e 100 perldiag Perl diagnostic messages
41630250 101 perllexwarn Perl warnings and their control
4755096e 102 perldebug Perl debugging
fb9cefb4 103 perlvar Perl predefined variables
4755096e 104 perlre Perl regular expressions, the rest of the story
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105 perlrebackslash Perl regular expression backslash sequences
106 perlrecharclass Perl regular expression character classes
30487ceb 107 perlreref Perl regular expressions quick reference
d396a558 108 perlref Perl references, the rest of the story
fb9cefb4 109 perlform Perl formats
d396a558 110 perlobj Perl objects
d396a558 111 perltie Perl objects hidden behind simple variables
fd7b6849 112 perldbmfilter Perl DBM filters
760ac839 113
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114 perlipc Perl interprocess communication
115 perlfork Perl fork() information
116 perlnumber Perl number semantics
53d7eaa8 117
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118 perlthrtut Perl threads tutorial
119
120 perlport Perl portability guide
d396a558 121 perllocale Perl locale support
07fcf8ff 122 perluniintro Perl Unicode introduction
41630250 123 perlunicode Perl Unicode support
3426ea3d 124 perlunifaq Perl Unicode FAQ
0cb5a9a8 125 perluniprops Index of Unicode properties in Perl
aadaa455 126 perlunitut Perl Unicode tutorial
d396a558 127 perlebcdic Considerations for running Perl on EBCDIC platforms
c2e66d9e 128
d396a558 129 perlsec Perl security
4755096e 130
c2e66d9e 131 perlmod Perl modules: how they work
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132 perlmodlib Perl modules: how to write and use
133 perlmodstyle Perl modules: how to write modules with style
fd7b6849 134 perlmodinstall Perl modules: how to install from CPAN
c2e66d9e 135 perlnewmod Perl modules: preparing a new module for distribution
a550ee30 136 perlpragma Perl modules: writing a user pragma
760ac839 137
fd7b6849 138 perlutil utilities packaged with the Perl distribution
760ac839 139
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140 perlfilter Perl source filters
141
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142 perldtrace Perl's support for DTrace
143
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144 perlglossary Perl Glossary
145
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146=head2 Internals and C Language Interface
147
fb9cefb4 148 perlembed Perl ways to embed perl in your C or C++ application
41630250 149 perldebguts Perl debugging guts and tips
fb9cefb4 150 perlxstut Perl XS tutorial
4755096e 151 perlxs Perl XS application programming interface
0eb29def 152 perlxstypemap Perl XS C/Perl type conversion tools
f40a6c71 153 perlclib Internal replacements for standard C library functions
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154 perlguts Perl internal functions for those doing extensions
155 perlcall Perl calling conventions from C
15932acc 156 perlmroapi Perl method resolution plugin interface
108003db 157 perlreapi Perl regular expression plugin interface
b23a565d 158 perlreguts Perl regular expression engine internals
fd7b6849 159
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160 perlapi Perl API listing (autogenerated)
161 perlintern Perl internal functions (autogenerated)
dc5c060f 162 perliol C API for Perl's implementation of IO in Layers
4755096e 163 perlapio Perl internal IO abstraction interface
fd7b6849 164
e8cd7eae 165 perlhack Perl hackers guide
04c692a8 166 perlsource Guide to the Perl source tree
1c2e8cca 167 perlinterp Overview of the Perl interpreter source and how it works
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168 perlhacktut Walk through the creation of a simple C code patch
169 perlhacktips Tips for Perl core C code hacking
cb8a010e 170 perlpolicy Perl development policies
04c692a8 171 perlgit Using git with the Perl repository
4755096e 172
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173=head2 Miscellaneous
174
175 perlbook Perl book information
cbd87e7e 176 perlcommunity Perl community information
fd7b6849 177
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178 perldoc Look up Perl documentation in Pod format
179
fb9cefb4 180 perlhist Perl history records
bdfb6cc8 181 perldelta Perl changes since previous version
7e7cfa2d 182 perl5175delta Perl changes in version 5.17.5
5d8c8c8a 183 perl5174delta Perl changes in version 5.17.4
916c45d9 184 perl5173delta Perl changes in version 5.17.3
4eabcf70 185 perl5172delta Perl changes in version 5.17.2
e96e0834 186 perl5171delta Perl changes in version 5.17.1
61174fb5 187 perl5170delta Perl changes in version 5.17.0
69cb649c 188 perl5161delta Perl changes in version 5.16.1
50f27400 189 perl5162delta Perl changes in version 5.16.2
05c8f9ed 190 perl5160delta Perl changes in version 5.16.0
70ce046e 191 perl5143delta Perl changes in version 5.14.3
77efd0f7 192 perl5142delta Perl changes in version 5.14.2
10288c7a 193 perl5141delta Perl changes in version 5.14.1
066dc4d9 194 perl5140delta Perl changes in version 5.14.0
0b67f426 195 perl5124delta Perl changes in version 5.12.4
6c5f5efa 196 perl5123delta Perl changes in version 5.12.3
e71d1a7d 197 perl5122delta Perl changes in version 5.12.2
bdfb6cc8 198 perl5121delta Perl changes in version 5.12.1
20d57231 199 perl5120delta Perl changes in version 5.12.0
7cdf958d 200 perl5101delta Perl changes in version 5.10.1
7120b314 201 perl5100delta Perl changes in version 5.10.0
fc5be808 202 perl589delta Perl changes in version 5.8.9
c11a53c6 203 perl588delta Perl changes in version 5.8.8
315ba985 204 perl587delta Perl changes in version 5.8.7
e4bb216d 205 perl586delta Perl changes in version 5.8.6
07e9b5fe 206 perl585delta Perl changes in version 5.8.5
5f15c94e 207 perl584delta Perl changes in version 5.8.4
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208 perl583delta Perl changes in version 5.8.3
209 perl582delta Perl changes in version 5.8.2
b6235c4f 210 perl581delta Perl changes in version 5.8.1
2e038148 211 perl58delta Perl changes in version 5.8.0
493a87da 212 perl561delta Perl changes in version 5.6.1
41630250 213 perl56delta Perl changes in version 5.6
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214 perl5005delta Perl changes in version 5.005
215 perl5004delta Perl changes in version 5.004
d516a115 216
42e73e1c 217 perlexperiment A listing of experimental features in Perl
218
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219 perlartistic Perl Artistic License
220 perlgpl GNU General Public License
221
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222=head2 Language-Specific
223
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224=for buildtoc flag +r
225
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226 perlcn Perl for Simplified Chinese (in EUC-CN)
227 perljp Perl for Japanese (in EUC-JP)
228 perlko Perl for Korean (in EUC-KR)
229 perltw Perl for Traditional Chinese (in Big5)
230
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231=head2 Platform-Specific
232
37d4d706 233 perlaix Perl notes for AIX
a83b6f46 234 perlamiga Perl notes for AmigaOS
a83b6f46 235 perlbeos Perl notes for BeOS
dc5c060f 236 perlbs2000 Perl notes for POSIX-BC BS2000
a1f19229 237 perlce Perl notes for WinCE
49877630 238 perlcygwin Perl notes for Cygwin
245d750e 239 perldgux Perl notes for DG/UX
49877630 240 perldos Perl notes for DOS
9a997319 241 perlepoc Perl notes for EPOC
41630250 242 perlfreebsd Perl notes for FreeBSD
f6706af3 243 perlhaiku Perl notes for Haiku
49877630 244 perlhpux Perl notes for HP-UX
a83b6f46 245 perlhurd Perl notes for Hurd
469e7be4 246 perlirix Perl notes for Irix
991e8403 247 perllinux Perl notes for Linux
26d9b02f 248 perlmacos Perl notes for Mac OS (Classic)
0d53b15f 249 perlmacosx Perl notes for Mac OS X
41630250 250 perlnetware Perl notes for NetWare
b0846812 251 perlopenbsd Perl notes for OpenBSD
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252 perlos2 Perl notes for OS/2
253 perlos390 Perl notes for OS/390
522b859a 254 perlos400 Perl notes for OS/400
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255 perlplan9 Perl notes for Plan 9
256 perlqnx Perl notes for QNX
2f08ed66 257 perlriscos Perl notes for RISC OS
d420ca49 258 perlsolaris Perl notes for Solaris
27da23d5 259 perlsymbian Perl notes for Symbian
772ff3b9 260 perltru64 Perl notes for Tru64
49877630 261 perlvms Perl notes for VMS
9a997319 262 perlvos Perl notes for Stratus VOS
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263 perlwin32 Perl notes for Windows
264
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265=for buildtoc flag -r
266
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267=head2 Stubs for Deleted Documents
268
269 perlboot
270 perlbot
5d0b49e8 271 perltodo
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272 perltooc
273 perltoot
274
0aef0fe5 275=for buildtoc __END__
35dec5db 276
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277On a Unix-like system, these documentation files will usually also be
278available as manpages for use with the F<man> program.
a0d0e21e 279
6b43eec4 280In general, if something strange has gone wrong with your program and you're
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281not sure where you should look for help, try making your code comply with
282B<use strict> and B<use warnings>. These will often point out exactly
283where the trouble is.
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284
285=head1 DESCRIPTION
286
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287Perl officially stands for Practical Extraction and Report Language,
288except when it doesn't.
289
72033c14 290Perl was originally a language optimized for scanning arbitrary
a0d0e21e 291text files, extracting information from those text files, and printing
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292reports based on that information. It quickly became a good language
293for many system management tasks. Over the years, Perl has grown into
b6538e4f 294a general-purpose programming language. It's widely used for everything
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295from quick "one-liners" to full-scale application development.
296
297The language is intended to be practical (easy to use, efficient,
298complete) rather than beautiful (tiny, elegant, minimal).
94d58c47 299
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300Perl combines (in the author's opinion, anyway) some of the best
301features of C, B<sed>, B<awk>, and B<sh>, so people familiar with
302those languages should have little difficulty with it. (Language
303historians will also note some vestiges of B<csh>, Pascal, and even
14218588 304BASIC-PLUS.) Expression syntax corresponds closely to C
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305expression syntax. Unlike most Unix utilities, Perl does not
306arbitrarily limit the size of your data--if you've got the memory,
aa689395 307Perl can slurp in your whole file as a single string. Recursion is of
0f31cffe 308unlimited depth. And the tables used by hashes (sometimes called
aa689395 309"associative arrays") grow as necessary to prevent degraded
0f31cffe 310performance. Perl can use sophisticated pattern matching techniques to
14218588 311scan large amounts of data quickly. Although optimized for
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312scanning text, Perl also has many excellent tools for slicing
313and dicing binary data.
aa689395 314
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315But wait, there's more...
316
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317Begun in 1993 (see L<perlhist>), Perl version 5 is nearly a complete
318rewrite that provides the following additional benefits:
a0d0e21e 319
13a2d996 320=over 4
a0d0e21e 321
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322=item *
323
324modularity and reusability using innumerable modules
a0d0e21e 325
19799a22 326Described in L<perlmod>, L<perlmodlib>, and L<perlmodinstall>.
a0d0e21e 327
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328=item *
329
330embeddable and extensible
a0d0e21e 331
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332Described in L<perlembed>, L<perlxstut>, L<perlxs>, L<perlxstypemap>,
333L<perlcall>, L<perlguts>, and L<xsubpp>.
a0d0e21e 334
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335=item *
336
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337roll-your-own magic variables (including multiple simultaneous DBM
338implementations)
a0d0e21e 339
19799a22 340Described in L<perltie> and L<AnyDBM_File>.
a0d0e21e 341
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342=item *
343
344subroutines can now be overridden, autoloaded, and prototyped
a0d0e21e 345
19799a22 346Described in L<perlsub>.
a0d0e21e 347
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348=item *
349
350arbitrarily nested data structures and anonymous functions
a0d0e21e 351
19799a22 352Described in L<perlreftut>, L<perlref>, L<perldsc>, and L<perllol>.
a0d0e21e 353
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354=item *
355
356object-oriented programming
a0d0e21e 357
82e1c0d9 358Described in L<perlobj> and L<perlootut>.
a0d0e21e 359
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360=item *
361
551e1d92 362support for light-weight processes (threads)
a0d0e21e 363
63de3cb2 364Described in L<perlthrtut> and L<threads>.
a0d0e21e 365
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366=item *
367
63de3cb2 368support for Unicode, internationalization, and localization
a0d0e21e 369
63de3cb2 370Described in L<perluniintro>, L<perllocale> and L<Locale::Maketext>.
a0d0e21e 371
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372=item *
373
374lexical scoping
a0d0e21e 375
19799a22 376Described in L<perlsub>.
a0d0e21e 377
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378=item *
379
380regular expression enhancements
a0d0e21e 381
19799a22 382Described in L<perlre>, with additional examples in L<perlop>.
a0d0e21e 383
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384=item *
385
386enhanced debugger and interactive Perl environment,
387with integrated editor support
a0d0e21e 388
f6b3c421 389Described in L<perldebtut>, L<perldebug> and L<perldebguts>.
a0d0e21e 390
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391=item *
392
393POSIX 1003.1 compliant library
5f05dabc 394
19799a22 395Described in L<POSIX>.
5f05dabc 396
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397=back
398
68dc0745 399Okay, that's I<definitely> enough hype.
a0d0e21e 400
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401=head1 AVAILABILITY
402
14218588 403Perl is available for most operating systems, including virtually
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404all Unix-like platforms. See L<perlport/"Supported Platforms">
405for a listing.
8bc4a6bb 406
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407=head1 ENVIRONMENT
408
1e422769 409See L<perlrun>.
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410
411=head1 AUTHOR
412
19799a22 413Larry Wall <larry@wall.org>, with the help of oodles of other folks.
a0d0e21e 414
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415If your Perl success stories and testimonials may be of help to others
416who wish to advocate the use of Perl in their applications,
417or if you wish to simply express your gratitude to Larry and the
19799a22 418Perl developers, please write to perl-thanks@perl.org .
a99b1639 419
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420=head1 FILES
421
5f05dabc 422 "@INC" locations of perl libraries
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423
424=head1 SEE ALSO
425
c5f69108 426 http://www.perl.org/ the Perl homepage
da9e6348 427 http://www.perl.com/ Perl articles (O'Reilly)
f6b3c421 428 http://www.cpan.org/ the Comprehensive Perl Archive
c5f69108 429 http://www.pm.org/ the Perl Mongers
19799a22 430
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431=head1 DIAGNOSTICS
432
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433Using the C<use strict> pragma ensures that all variables are properly
434declared and prevents other misuses of legacy Perl features.
435
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436The C<use warnings> pragma produces some lovely diagnostics. One can
437also use the B<-w> flag, but its use is normally discouraged, because
438it gets applied to all executed Perl code, including that not under
439your control.
a0d0e21e 440
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441See L<perldiag> for explanations of all Perl's diagnostics. The C<use
442diagnostics> pragma automatically turns Perl's normally terse warnings
443and errors into these longer forms.
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444
445Compilation errors will tell you the line number of the error, with an
446indication of the next token or token type that was to be examined.
14218588 447(In a script passed to Perl via B<-e> switches, each
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448B<-e> is counted as one line.)
449
450Setuid scripts have additional constraints that can produce error
451messages such as "Insecure dependency". See L<perlsec>.
452
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453Did we mention that you should definitely consider using the B<use warnings>
454pragma?
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455
456=head1 BUGS
457
71b5b092 458The behavior implied by the B<use warnings> pragma is not mandatory.
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459
460Perl is at the mercy of your machine's definitions of various
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461operations such as type casting, atof(), and floating-point
462output with sprintf().
a0d0e21e 463
748a9306 464If your stdio requires a seek or eof between reads and writes on a
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465particular stream, so does Perl. (This doesn't apply to sysread()
466and syswrite().)
467
468While none of the built-in data types have any arbitrary size limits
469(apart from memory size), there are still a few arbitrary limits: a
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470given variable name may not be longer than 251 characters. Line numbers
471displayed by diagnostics are internally stored as short integers,
472so they are limited to a maximum of 65535 (higher numbers usually being
473affected by wraparound).
a0d0e21e 474
b0607b7a 475You may mail your bug reports (be sure to include full configuration
19799a22 476information as output by the myconfig program in the perl source
7f2de2d2 477tree, or by C<perl -V>) to perlbug@perl.org . If you've succeeded
7f89f796 478in compiling perl, the L<perlbug> script in the F<utils/> subdirectory
19799a22 479can be used to help mail in a bug report.
4633a7c4 480
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481Perl actually stands for Pathologically Eclectic Rubbish Lister, but
482don't tell anyone I said that.
483
484=head1 NOTES
485
486The Perl motto is "There's more than one way to do it." Divining
487how many more is left as an exercise to the reader.
488
4633a7c4 489The three principal virtues of a programmer are Laziness,
a0d0e21e 490Impatience, and Hubris. See the Camel Book for why.
16d20bd9 491