This is a live mirror of the Perl 5 development currently hosted at https://github.com/perl/perl5
Create new perldelta for 5.21.12 (although it's unlikely to happen)
[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/
cb1974ba 45path perldoc cpan/Pod-Perldoc/
0aef0fe5 46
c67aee7a 47aux c2ph 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
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
5dd47fd4 124 perlunicook Perl Unicode cookbook
3426ea3d 125 perlunifaq Perl Unicode FAQ
0cb5a9a8 126 perluniprops Index of Unicode properties in Perl
aadaa455 127 perlunitut Perl Unicode tutorial
d396a558 128 perlebcdic Considerations for running Perl on EBCDIC platforms
c2e66d9e 129
d396a558 130 perlsec Perl security
4755096e 131
c2e66d9e 132 perlmod Perl modules: how they work
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133 perlmodlib Perl modules: how to write and use
134 perlmodstyle Perl modules: how to write modules with style
fd7b6849 135 perlmodinstall Perl modules: how to install from CPAN
c2e66d9e 136 perlnewmod Perl modules: preparing a new module for distribution
a550ee30 137 perlpragma Perl modules: writing a user pragma
760ac839 138
fd7b6849 139 perlutil utilities packaged with the Perl distribution
760ac839 140
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141 perlfilter Perl source filters
142
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143 perldtrace Perl's support for DTrace
144
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145 perlglossary Perl Glossary
146
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147=head2 Internals and C Language Interface
148
fb9cefb4 149 perlembed Perl ways to embed perl in your C or C++ application
41630250 150 perldebguts Perl debugging guts and tips
fb9cefb4 151 perlxstut Perl XS tutorial
4755096e 152 perlxs Perl XS application programming interface
0eb29def 153 perlxstypemap Perl XS C/Perl type conversion tools
f40a6c71 154 perlclib Internal replacements for standard C library functions
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155 perlguts Perl internal functions for those doing extensions
156 perlcall Perl calling conventions from C
15932acc 157 perlmroapi Perl method resolution plugin interface
108003db 158 perlreapi Perl regular expression plugin interface
b23a565d 159 perlreguts Perl regular expression engine internals
fd7b6849 160
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161 perlapi Perl API listing (autogenerated)
162 perlintern Perl internal functions (autogenerated)
dc5c060f 163 perliol C API for Perl's implementation of IO in Layers
4755096e 164 perlapio Perl internal IO abstraction interface
fd7b6849 165
e8cd7eae 166 perlhack Perl hackers guide
04c692a8 167 perlsource Guide to the Perl source tree
1c2e8cca 168 perlinterp Overview of the Perl interpreter source and how it works
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169 perlhacktut Walk through the creation of a simple C code patch
170 perlhacktips Tips for Perl core C code hacking
cb8a010e 171 perlpolicy Perl development policies
04c692a8 172 perlgit Using git with the Perl repository
4755096e 173
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174=head2 Miscellaneous
175
176 perlbook Perl book information
cbd87e7e 177 perlcommunity Perl community information
fd7b6849 178
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179 perldoc Look up Perl documentation in Pod format
180
fb9cefb4 181 perlhist Perl history records
bdfb6cc8 182 perldelta Perl changes since previous version
7f9fef93 183 perl52111delta Perl changes in version 5.21.11
e5998677 184 perl52110delta Perl changes in version 5.21.10
a9c3e753 185 perl5219delta Perl changes in version 5.21.9
2ff1ebfe 186 perl5218delta Perl changes in version 5.21.8
b5d4d3b9 187 perl5217delta Perl changes in version 5.21.7
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188 perl5216delta Perl changes in version 5.21.6
189 perl5215delta Perl changes in version 5.21.5
190 perl5214delta Perl changes in version 5.21.4
191 perl5213delta Perl changes in version 5.21.3
192 perl5212delta Perl changes in version 5.21.2
193 perl5211delta Perl changes in version 5.21.1
194 perl5210delta Perl changes in version 5.21.0
2b85b119 195 perl5202delta Perl changes in version 5.20.2
0c54b9fe 196 perl5201delta Perl changes in version 5.20.1
d1148309 197 perl5200delta Perl changes in version 5.20.0
e990b849 198 perl5184delta Perl changes in version 5.18.4
7b97958f 199 perl5182delta Perl changes in version 5.18.2
f4e35152 200 perl5181delta Perl changes in version 5.18.1
f13a3008 201 perl5180delta Perl changes in version 5.18.0
eaf7bcbf 202 perl5163delta Perl changes in version 5.16.3
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203 perl5162delta Perl changes in version 5.16.2
204 perl5161delta Perl changes in version 5.16.1
05c8f9ed 205 perl5160delta Perl changes in version 5.16.0
1e5cc764 206 perl5144delta Perl changes in version 5.14.4
70ce046e 207 perl5143delta Perl changes in version 5.14.3
77efd0f7 208 perl5142delta Perl changes in version 5.14.2
10288c7a 209 perl5141delta Perl changes in version 5.14.1
066dc4d9 210 perl5140delta Perl changes in version 5.14.0
a5caed3e 211 perl5125delta Perl changes in version 5.12.5
0b67f426 212 perl5124delta Perl changes in version 5.12.4
6c5f5efa 213 perl5123delta Perl changes in version 5.12.3
e71d1a7d 214 perl5122delta Perl changes in version 5.12.2
bdfb6cc8 215 perl5121delta Perl changes in version 5.12.1
20d57231 216 perl5120delta Perl changes in version 5.12.0
7cdf958d 217 perl5101delta Perl changes in version 5.10.1
7120b314 218 perl5100delta Perl changes in version 5.10.0
fc5be808 219 perl589delta Perl changes in version 5.8.9
c11a53c6 220 perl588delta Perl changes in version 5.8.8
315ba985 221 perl587delta Perl changes in version 5.8.7
e4bb216d 222 perl586delta Perl changes in version 5.8.6
07e9b5fe 223 perl585delta Perl changes in version 5.8.5
5f15c94e 224 perl584delta Perl changes in version 5.8.4
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225 perl583delta Perl changes in version 5.8.3
226 perl582delta Perl changes in version 5.8.2
b6235c4f 227 perl581delta Perl changes in version 5.8.1
2e038148 228 perl58delta Perl changes in version 5.8.0
493a87da 229 perl561delta Perl changes in version 5.6.1
41630250 230 perl56delta Perl changes in version 5.6
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231 perl5005delta Perl changes in version 5.005
232 perl5004delta Perl changes in version 5.004
d516a115 233
42e73e1c 234 perlexperiment A listing of experimental features in Perl
235
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236 perlartistic Perl Artistic License
237 perlgpl GNU General Public License
238
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239=head2 Language-Specific
240
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241=for buildtoc flag +r
242
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243 perlcn Perl for Simplified Chinese (in EUC-CN)
244 perljp Perl for Japanese (in EUC-JP)
245 perlko Perl for Korean (in EUC-KR)
246 perltw Perl for Traditional Chinese (in Big5)
247
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248=head2 Platform-Specific
249
37d4d706 250 perlaix Perl notes for AIX
a83b6f46 251 perlamiga Perl notes for AmigaOS
6001596e 252 perlandroid Perl notes for Android
dc5c060f 253 perlbs2000 Perl notes for POSIX-BC BS2000
a1f19229 254 perlce Perl notes for WinCE
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255 perlcygwin Perl notes for Cygwin
256 perldos Perl notes for DOS
41630250 257 perlfreebsd Perl notes for FreeBSD
f6706af3 258 perlhaiku Perl notes for Haiku
49877630 259 perlhpux Perl notes for HP-UX
a83b6f46 260 perlhurd Perl notes for Hurd
469e7be4 261 perlirix Perl notes for Irix
991e8403 262 perllinux Perl notes for Linux
26d9b02f 263 perlmacos Perl notes for Mac OS (Classic)
0d53b15f 264 perlmacosx Perl notes for Mac OS X
41630250 265 perlnetware Perl notes for NetWare
b0846812 266 perlopenbsd Perl notes for OpenBSD
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267 perlos2 Perl notes for OS/2
268 perlos390 Perl notes for OS/390
522b859a 269 perlos400 Perl notes for OS/400
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270 perlplan9 Perl notes for Plan 9
271 perlqnx Perl notes for QNX
2f08ed66 272 perlriscos Perl notes for RISC OS
d420ca49 273 perlsolaris Perl notes for Solaris
27da23d5 274 perlsymbian Perl notes for Symbian
58534900 275 perlsynology Perl notes for Synology
772ff3b9 276 perltru64 Perl notes for Tru64
49877630 277 perlvms Perl notes for VMS
9a997319 278 perlvos Perl notes for Stratus VOS
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279 perlwin32 Perl notes for Windows
280
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281=for buildtoc flag -r
282
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283=head2 Stubs for Deleted Documents
284
285 perlboot
286 perlbot
9ab63835 287 perlrepository
5d0b49e8 288 perltodo
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289 perltooc
290 perltoot
291
0aef0fe5 292=for buildtoc __END__
35dec5db 293
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294On a Unix-like system, these documentation files will usually also be
295available as manpages for use with the F<man> program.
a0d0e21e 296
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297Some documentation is not available as man pages, so if a
298cross-reference is not found by man, try it with L<perldoc>. Perldoc can
299also take you directly to documentation for functions (with the B<-f>
300switch). See C<perldoc --help> (or C<perldoc perldoc> or C<man perldoc>)
301for other helpful options L<perldoc> has to offer.
302
6b43eec4 303In general, if something strange has gone wrong with your program and you're
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304not sure where you should look for help, try making your code comply with
305B<use strict> and B<use warnings>. These will often point out exactly
306where the trouble is.
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307
308=head1 DESCRIPTION
309
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310Perl officially stands for Practical Extraction and Report Language,
311except when it doesn't.
312
72033c14 313Perl was originally a language optimized for scanning arbitrary
a0d0e21e 314text files, extracting information from those text files, and printing
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315reports based on that information. It quickly became a good language
316for many system management tasks. Over the years, Perl has grown into
b6538e4f 317a general-purpose programming language. It's widely used for everything
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318from quick "one-liners" to full-scale application development.
319
320The language is intended to be practical (easy to use, efficient,
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321complete) rather than beautiful (tiny, elegant, minimal). It combines
322(in the author's opinion, anyway) some of the best features of B<sed>,
0e7bd06d 323B<awk>, and B<sh>, making it familiar and easy to use for Unix users to
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324whip up quick solutions to annoying problems. Its general-purpose
325programming facilities support procedural, functional, and
326object-oriented programming paradigms, making Perl a comfortable
327language for the long haul on major projects, whatever your bent.
328
329Perl's roots in text processing haven't been forgotten over the years.
330It still boasts some of the most powerful regular expressions to be
331found anywhere, and its support for Unicode text is world-class. It
332handles all kinds of structured text, too, through an extensive
333collection of extensions. Those libraries, collected in the CPAN,
334provide ready-made solutions to an astounding array of problems. When
335they haven't set the standard themselves, they steal from the best
336-- just like Perl itself.
a0d0e21e 337
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338=head1 AVAILABILITY
339
14218588 340Perl is available for most operating systems, including virtually
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341all Unix-like platforms. See L<perlport/"Supported Platforms">
342for a listing.
8bc4a6bb 343
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344=head1 ENVIRONMENT
345
1e422769 346See L<perlrun>.
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347
348=head1 AUTHOR
349
19799a22 350Larry Wall <larry@wall.org>, with the help of oodles of other folks.
a0d0e21e 351
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352If your Perl success stories and testimonials may be of help to others
353who wish to advocate the use of Perl in their applications,
354or if you wish to simply express your gratitude to Larry and the
19799a22 355Perl developers, please write to perl-thanks@perl.org .
a99b1639 356
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357=head1 FILES
358
5f05dabc 359 "@INC" locations of perl libraries
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360
361=head1 SEE ALSO
362
c5f69108 363 http://www.perl.org/ the Perl homepage
da9e6348 364 http://www.perl.com/ Perl articles (O'Reilly)
f6b3c421 365 http://www.cpan.org/ the Comprehensive Perl Archive
c5f69108 366 http://www.pm.org/ the Perl Mongers
19799a22 367
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368=head1 DIAGNOSTICS
369
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370Using the C<use strict> pragma ensures that all variables are properly
371declared and prevents other misuses of legacy Perl features.
372
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373The C<use warnings> pragma produces some lovely diagnostics. One can
374also use the B<-w> flag, but its use is normally discouraged, because
375it gets applied to all executed Perl code, including that not under
376your control.
a0d0e21e 377
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378See L<perldiag> for explanations of all Perl's diagnostics. The C<use
379diagnostics> pragma automatically turns Perl's normally terse warnings
380and errors into these longer forms.
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381
382Compilation errors will tell you the line number of the error, with an
383indication of the next token or token type that was to be examined.
14218588 384(In a script passed to Perl via B<-e> switches, each
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385B<-e> is counted as one line.)
386
387Setuid scripts have additional constraints that can produce error
388messages such as "Insecure dependency". See L<perlsec>.
389
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390Did we mention that you should definitely consider using the B<use warnings>
391pragma?
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392
393=head1 BUGS
394
71b5b092 395The behavior implied by the B<use warnings> pragma is not mandatory.
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396
397Perl is at the mercy of your machine's definitions of various
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398operations such as type casting, atof(), and floating-point
399output with sprintf().
a0d0e21e 400
748a9306 401If your stdio requires a seek or eof between reads and writes on a
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402particular stream, so does Perl. (This doesn't apply to sysread()
403and syswrite().)
404
405While none of the built-in data types have any arbitrary size limits
406(apart from memory size), there are still a few arbitrary limits: a
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407given variable name may not be longer than 251 characters. Line numbers
408displayed by diagnostics are internally stored as short integers,
409so they are limited to a maximum of 65535 (higher numbers usually being
410affected by wraparound).
a0d0e21e 411
b0607b7a 412You may mail your bug reports (be sure to include full configuration
19799a22 413information as output by the myconfig program in the perl source
7f2de2d2 414tree, or by C<perl -V>) to perlbug@perl.org . If you've succeeded
7f89f796 415in compiling perl, the L<perlbug> script in the F<utils/> subdirectory
19799a22 416can be used to help mail in a bug report.
4633a7c4 417
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418Perl actually stands for Pathologically Eclectic Rubbish Lister, but
419don't tell anyone I said that.
420
421=head1 NOTES
422
423The Perl motto is "There's more than one way to do it." Divining
424how many more is left as an exercise to the reader.
425
4633a7c4 426The three principal virtues of a programmer are Laziness,
a0d0e21e 427Impatience, and Hubris. See the Camel Book for why.
16d20bd9 428