This is a live mirror of the Perl 5 development currently hosted at https://github.com/perl/perl5
Import perl5282delta.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/
cb1974ba 45path perldoc cpan/Pod-Perldoc/
0aef0fe5 46
2560602c 47aux h2ph h2xs perlbug pl2pm pod2html pod2man splain xsubpp
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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
9021a1cf 101 perldeprecation Perl deprecations
41630250 102 perllexwarn Perl warnings and their control
4755096e 103 perldebug Perl debugging
fb9cefb4 104 perlvar Perl predefined variables
4755096e 105 perlre Perl regular expressions, the rest of the story
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106 perlrebackslash Perl regular expression backslash sequences
107 perlrecharclass Perl regular expression character classes
30487ceb 108 perlreref Perl regular expressions quick reference
d396a558 109 perlref Perl references, the rest of the story
fb9cefb4 110 perlform Perl formats
d396a558 111 perlobj Perl objects
d396a558 112 perltie Perl objects hidden behind simple variables
fd7b6849 113 perldbmfilter Perl DBM filters
760ac839 114
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115 perlipc Perl interprocess communication
116 perlfork Perl fork() information
117 perlnumber Perl number semantics
53d7eaa8 118
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119 perlthrtut Perl threads tutorial
120
121 perlport Perl portability guide
d396a558 122 perllocale Perl locale support
07fcf8ff 123 perluniintro Perl Unicode introduction
41630250 124 perlunicode Perl Unicode support
5dd47fd4 125 perlunicook Perl Unicode cookbook
3426ea3d 126 perlunifaq Perl Unicode FAQ
0cb5a9a8 127 perluniprops Index of Unicode properties in Perl
aadaa455 128 perlunitut Perl Unicode tutorial
d396a558 129 perlebcdic Considerations for running Perl on EBCDIC platforms
c2e66d9e 130
d396a558 131 perlsec Perl security
4755096e 132
c2e66d9e 133 perlmod Perl modules: how they work
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134 perlmodlib Perl modules: how to write and use
135 perlmodstyle Perl modules: how to write modules with style
fd7b6849 136 perlmodinstall Perl modules: how to install from CPAN
c2e66d9e 137 perlnewmod Perl modules: preparing a new module for distribution
a550ee30 138 perlpragma Perl modules: writing a user pragma
760ac839 139
fd7b6849 140 perlutil utilities packaged with the Perl distribution
760ac839 141
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142 perlfilter Perl source filters
143
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144 perldtrace Perl's support for DTrace
145
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146 perlglossary Perl Glossary
147
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148=head2 Internals and C Language Interface
149
fb9cefb4 150 perlembed Perl ways to embed perl in your C or C++ application
41630250 151 perldebguts Perl debugging guts and tips
fb9cefb4 152 perlxstut Perl XS tutorial
4755096e 153 perlxs Perl XS application programming interface
0eb29def 154 perlxstypemap Perl XS C/Perl type conversion tools
f40a6c71 155 perlclib Internal replacements for standard C library functions
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156 perlguts Perl internal functions for those doing extensions
157 perlcall Perl calling conventions from C
15932acc 158 perlmroapi Perl method resolution plugin interface
108003db 159 perlreapi Perl regular expression plugin interface
b23a565d 160 perlreguts Perl regular expression engine internals
fd7b6849 161
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162 perlapi Perl API listing (autogenerated)
163 perlintern Perl internal functions (autogenerated)
dc5c060f 164 perliol C API for Perl's implementation of IO in Layers
4755096e 165 perlapio Perl internal IO abstraction interface
fd7b6849 166
e8cd7eae 167 perlhack Perl hackers guide
04c692a8 168 perlsource Guide to the Perl source tree
1c2e8cca 169 perlinterp Overview of the Perl interpreter source and how it works
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170 perlhacktut Walk through the creation of a simple C code patch
171 perlhacktips Tips for Perl core C code hacking
cb8a010e 172 perlpolicy Perl development policies
04c692a8 173 perlgit Using git with the Perl repository
4755096e 174
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175=head2 Miscellaneous
176
177 perlbook Perl book information
cbd87e7e 178 perlcommunity Perl community information
fd7b6849 179
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180 perldoc Look up Perl documentation in Pod format
181
fb9cefb4 182 perlhist Perl history records
bdfb6cc8 183 perldelta Perl changes since previous version
ab6f2e91 184 perl5299delta Perl changes in version 5.29.9
0e18d1c4 185 perl5298delta Perl changes in version 5.29.8
65c75f8f 186 perl5297delta Perl changes in version 5.29.7
e0f0cf8a 187 perl5296delta Perl changes in version 5.29.6
4380f76d 188 perl5295delta Perl changes in version 5.29.5
4234ac96 189 perl5294delta Perl changes in version 5.29.4
21d34e95 190 perl5293delta Perl changes in version 5.29.3
7a54f67e 191 perl5292delta Perl changes in version 5.29.2
373fec1e 192 perl5291delta Perl changes in version 5.29.1
1060c83c 193 perl5290delta Perl changes in version 5.29.0
bea9954d 194 perl5282delta Perl changes in version 5.28.2
43323ad1 195 perl5281delta Perl changes in version 5.28.1
b0394755 196 perl5280delta Perl changes in version 5.28.0
43323ad1 197 perl5263delta Perl changes in version 5.26.3
fb51aa58 198 perl5262delta Perl changes in version 5.26.2
c592f515 199 perl5261delta Perl changes in version 5.26.1
b5cbfe35 200 perl5260delta Perl changes in version 5.26.0
fb51aa58 201 perl5244delta Perl changes in version 5.24.4
c592f515 202 perl5243delta Perl changes in version 5.24.3
50d330d7 203 perl5242delta Perl changes in version 5.24.2
f4a48a9e 204 perl5241delta Perl changes in version 5.24.1
4b8803f0 205 perl5240delta Perl changes in version 5.24.0
50d330d7 206 perl5224delta Perl changes in version 5.22.4
f4a48a9e 207 perl5223delta Perl changes in version 5.22.3
2f7cab8b 208 perl5222delta Perl changes in version 5.22.2
fd5868f3 209 perl5221delta Perl changes in version 5.22.1
2cfe9b50 210 perl5220delta Perl changes in version 5.22.0
9fd420ca 211 perl5203delta Perl changes in version 5.20.3
2b85b119 212 perl5202delta Perl changes in version 5.20.2
0c54b9fe 213 perl5201delta Perl changes in version 5.20.1
d1148309 214 perl5200delta Perl changes in version 5.20.0
e990b849 215 perl5184delta Perl changes in version 5.18.4
7b97958f 216 perl5182delta Perl changes in version 5.18.2
f4e35152 217 perl5181delta Perl changes in version 5.18.1
f13a3008 218 perl5180delta Perl changes in version 5.18.0
eaf7bcbf 219 perl5163delta Perl changes in version 5.16.3
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220 perl5162delta Perl changes in version 5.16.2
221 perl5161delta Perl changes in version 5.16.1
05c8f9ed 222 perl5160delta Perl changes in version 5.16.0
1e5cc764 223 perl5144delta Perl changes in version 5.14.4
70ce046e 224 perl5143delta Perl changes in version 5.14.3
77efd0f7 225 perl5142delta Perl changes in version 5.14.2
10288c7a 226 perl5141delta Perl changes in version 5.14.1
066dc4d9 227 perl5140delta Perl changes in version 5.14.0
a5caed3e 228 perl5125delta Perl changes in version 5.12.5
0b67f426 229 perl5124delta Perl changes in version 5.12.4
6c5f5efa 230 perl5123delta Perl changes in version 5.12.3
e71d1a7d 231 perl5122delta Perl changes in version 5.12.2
bdfb6cc8 232 perl5121delta Perl changes in version 5.12.1
20d57231 233 perl5120delta Perl changes in version 5.12.0
7cdf958d 234 perl5101delta Perl changes in version 5.10.1
7120b314 235 perl5100delta Perl changes in version 5.10.0
fc5be808 236 perl589delta Perl changes in version 5.8.9
c11a53c6 237 perl588delta Perl changes in version 5.8.8
315ba985 238 perl587delta Perl changes in version 5.8.7
e4bb216d 239 perl586delta Perl changes in version 5.8.6
07e9b5fe 240 perl585delta Perl changes in version 5.8.5
5f15c94e 241 perl584delta Perl changes in version 5.8.4
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242 perl583delta Perl changes in version 5.8.3
243 perl582delta Perl changes in version 5.8.2
b6235c4f 244 perl581delta Perl changes in version 5.8.1
2e038148 245 perl58delta Perl changes in version 5.8.0
493a87da 246 perl561delta Perl changes in version 5.6.1
41630250 247 perl56delta Perl changes in version 5.6
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248 perl5005delta Perl changes in version 5.005
249 perl5004delta Perl changes in version 5.004
d516a115 250
42e73e1c 251 perlexperiment A listing of experimental features in Perl
252
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253 perlartistic Perl Artistic License
254 perlgpl GNU General Public License
255
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256=head2 Language-Specific
257
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258=for buildtoc flag +r
259
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260 perlcn Perl for Simplified Chinese (in EUC-CN)
261 perljp Perl for Japanese (in EUC-JP)
262 perlko Perl for Korean (in EUC-KR)
263 perltw Perl for Traditional Chinese (in Big5)
264
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265=head2 Platform-Specific
266
37d4d706 267 perlaix Perl notes for AIX
a83b6f46 268 perlamiga Perl notes for AmigaOS
6001596e 269 perlandroid Perl notes for Android
dc5c060f 270 perlbs2000 Perl notes for POSIX-BC BS2000
a1f19229 271 perlce Perl notes for WinCE
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272 perlcygwin Perl notes for Cygwin
273 perldos Perl notes for DOS
41630250 274 perlfreebsd Perl notes for FreeBSD
f6706af3 275 perlhaiku Perl notes for Haiku
49877630 276 perlhpux Perl notes for HP-UX
a83b6f46 277 perlhurd Perl notes for Hurd
469e7be4 278 perlirix Perl notes for Irix
991e8403 279 perllinux Perl notes for Linux
26d9b02f 280 perlmacos Perl notes for Mac OS (Classic)
0d53b15f 281 perlmacosx Perl notes for Mac OS X
41630250 282 perlnetware Perl notes for NetWare
b0846812 283 perlopenbsd Perl notes for OpenBSD
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284 perlos2 Perl notes for OS/2
285 perlos390 Perl notes for OS/390
522b859a 286 perlos400 Perl notes for OS/400
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287 perlplan9 Perl notes for Plan 9
288 perlqnx Perl notes for QNX
2f08ed66 289 perlriscos Perl notes for RISC OS
d420ca49 290 perlsolaris Perl notes for Solaris
27da23d5 291 perlsymbian Perl notes for Symbian
58534900 292 perlsynology Perl notes for Synology
772ff3b9 293 perltru64 Perl notes for Tru64
49877630 294 perlvms Perl notes for VMS
9a997319 295 perlvos Perl notes for Stratus VOS
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296 perlwin32 Perl notes for Windows
297
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298=for buildtoc flag -r
299
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300=head2 Stubs for Deleted Documents
301
302 perlboot
303 perlbot
9ab63835 304 perlrepository
5d0b49e8 305 perltodo
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306 perltooc
307 perltoot
308
0aef0fe5 309=for buildtoc __END__
35dec5db 310
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311On a Unix-like system, these documentation files will usually also be
312available as manpages for use with the F<man> program.
a0d0e21e 313
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314Some documentation is not available as man pages, so if a
315cross-reference is not found by man, try it with L<perldoc>. Perldoc can
316also take you directly to documentation for functions (with the B<-f>
317switch). See C<perldoc --help> (or C<perldoc perldoc> or C<man perldoc>)
318for other helpful options L<perldoc> has to offer.
319
6b43eec4 320In general, if something strange has gone wrong with your program and you're
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321not sure where you should look for help, try making your code comply with
322B<use strict> and B<use warnings>. These will often point out exactly
323where the trouble is.
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324
325=head1 DESCRIPTION
326
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327Perl officially stands for Practical Extraction and Report Language,
328except when it doesn't.
329
72033c14 330Perl was originally a language optimized for scanning arbitrary
a0d0e21e 331text files, extracting information from those text files, and printing
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332reports based on that information. It quickly became a good language
333for many system management tasks. Over the years, Perl has grown into
b6538e4f 334a general-purpose programming language. It's widely used for everything
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335from quick "one-liners" to full-scale application development.
336
337The language is intended to be practical (easy to use, efficient,
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338complete) rather than beautiful (tiny, elegant, minimal). It combines
339(in the author's opinion, anyway) some of the best features of B<sed>,
0e7bd06d 340B<awk>, and B<sh>, making it familiar and easy to use for Unix users to
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341whip up quick solutions to annoying problems. Its general-purpose
342programming facilities support procedural, functional, and
343object-oriented programming paradigms, making Perl a comfortable
344language for the long haul on major projects, whatever your bent.
345
346Perl's roots in text processing haven't been forgotten over the years.
347It still boasts some of the most powerful regular expressions to be
348found anywhere, and its support for Unicode text is world-class. It
349handles all kinds of structured text, too, through an extensive
350collection of extensions. Those libraries, collected in the CPAN,
351provide ready-made solutions to an astounding array of problems. When
352they haven't set the standard themselves, they steal from the best
353-- just like Perl itself.
a0d0e21e 354
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355=head1 AVAILABILITY
356
14218588 357Perl is available for most operating systems, including virtually
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358all Unix-like platforms. See L<perlport/"Supported Platforms">
359for a listing.
8bc4a6bb 360
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361=head1 ENVIRONMENT
362
1e422769 363See L<perlrun>.
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364
365=head1 AUTHOR
366
19799a22 367Larry Wall <larry@wall.org>, with the help of oodles of other folks.
a0d0e21e 368
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369If your Perl success stories and testimonials may be of help to others
370who wish to advocate the use of Perl in their applications,
371or if you wish to simply express your gratitude to Larry and the
19799a22 372Perl developers, please write to perl-thanks@perl.org .
a99b1639 373
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374=head1 FILES
375
5f05dabc 376 "@INC" locations of perl libraries
a0d0e21e 377
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378"@INC" above is a reference to the built-in variable of the same name;
379see L<perlvar> for more information.
380
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381=head1 SEE ALSO
382
c5f69108 383 http://www.perl.org/ the Perl homepage
da9e6348 384 http://www.perl.com/ Perl articles (O'Reilly)
f6b3c421 385 http://www.cpan.org/ the Comprehensive Perl Archive
c5f69108 386 http://www.pm.org/ the Perl Mongers
19799a22 387
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388=head1 DIAGNOSTICS
389
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390Using the C<use strict> pragma ensures that all variables are properly
391declared and prevents other misuses of legacy Perl features.
392
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393The C<use warnings> pragma produces some lovely diagnostics. One can
394also use the B<-w> flag, but its use is normally discouraged, because
395it gets applied to all executed Perl code, including that not under
396your control.
a0d0e21e 397
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398See L<perldiag> for explanations of all Perl's diagnostics. The C<use
399diagnostics> pragma automatically turns Perl's normally terse warnings
400and errors into these longer forms.
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401
402Compilation errors will tell you the line number of the error, with an
403indication of the next token or token type that was to be examined.
14218588 404(In a script passed to Perl via B<-e> switches, each
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405B<-e> is counted as one line.)
406
407Setuid scripts have additional constraints that can produce error
408messages such as "Insecure dependency". See L<perlsec>.
409
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410Did we mention that you should definitely consider using the B<use warnings>
411pragma?
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412
413=head1 BUGS
414
71b5b092 415The behavior implied by the B<use warnings> pragma is not mandatory.
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416
417Perl is at the mercy of your machine's definitions of various
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418operations such as type casting, atof(), and floating-point
419output with sprintf().
a0d0e21e 420
748a9306 421If your stdio requires a seek or eof between reads and writes on a
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422particular stream, so does Perl. (This doesn't apply to sysread()
423and syswrite().)
424
425While none of the built-in data types have any arbitrary size limits
426(apart from memory size), there are still a few arbitrary limits: a
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427given variable name may not be longer than 251 characters. Line numbers
428displayed by diagnostics are internally stored as short integers,
429so they are limited to a maximum of 65535 (higher numbers usually being
430affected by wraparound).
a0d0e21e 431
b0607b7a 432You may mail your bug reports (be sure to include full configuration
19799a22 433information as output by the myconfig program in the perl source
7f2de2d2 434tree, or by C<perl -V>) to perlbug@perl.org . If you've succeeded
7f89f796 435in compiling perl, the L<perlbug> script in the F<utils/> subdirectory
19799a22 436can be used to help mail in a bug report.
4633a7c4 437
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438Perl actually stands for Pathologically Eclectic Rubbish Lister, but
439don't tell anyone I said that.
440
441=head1 NOTES
442
443The Perl motto is "There's more than one way to do it." Divining
444how many more is left as an exercise to the reader.
445
4633a7c4 446The three principal virtues of a programmer are Laziness,
a0d0e21e 447Impatience, and Hubris. See the Camel Book for why.
16d20bd9 448