1PERL(1)                Perl Programmers Reference Guide                PERL(1)
2
3
4

NAME

6       perl - The Perl 5 language interpreter
7

SYNOPSIS

9       perl [ -sTtuUWX ]      [ -hv ] [ -V[:configvar] ]
10            [ -cw ] [ -d[t][:debugger] ] [ -D[number/list] ]
11            [ -pna ] [ -Fpattern ] [ -l[octal] ] [ -0[octal/hexadecimal] ]
12            [ -Idir ] [ -m[-]module ] [ -M[-]'module...' ] [ -f ]
13            [ -C [number/list] ]      [ -S ]      [ -x[dir] ]
14            [ -i[extension] ]
15            [ [-e|-E] 'command' ] [ -- ] [ programfile ] [ argument ]...
16
17       For more information on these options, you can run "perldoc perlrun".
18

GETTING HELP

20       The perldoc program gives you access to all the documentation that
21       comes with Perl.  You can get more documentation, tutorials and
22       community support online at <http://www.perl.org/>.
23
24       If you're new to Perl, you should start by running "perldoc perlintro",
25       which is a general intro for beginners and provides some background to
26       help you navigate the rest of Perl's extensive documentation.  Run
27       "perldoc perldoc" to learn more things you can do with perldoc.
28
29       For ease of access, the Perl manual has been split up into several
30       sections.
31
32   Overview
33           perl                Perl overview (this section)
34           perlintro           Perl introduction for beginners
35           perlrun             Perl execution and options
36           perltoc             Perl documentation table of contents
37
38   Tutorials
39           perlreftut          Perl references short introduction
40           perldsc             Perl data structures intro
41           perllol             Perl data structures: arrays of arrays
42
43           perlrequick         Perl regular expressions quick start
44           perlretut           Perl regular expressions tutorial
45
46           perlootut           Perl OO tutorial for beginners
47
48           perlperf            Perl Performance and Optimization Techniques
49
50           perlstyle           Perl style guide
51
52           perlcheat           Perl cheat sheet
53           perltrap            Perl traps for the unwary
54           perldebtut          Perl debugging tutorial
55
56           perlfaq             Perl frequently asked questions
57             perlfaq1          General Questions About Perl
58             perlfaq2          Obtaining and Learning about Perl
59             perlfaq3          Programming Tools
60             perlfaq4          Data Manipulation
61             perlfaq5          Files and Formats
62             perlfaq6          Regexes
63             perlfaq7          Perl Language Issues
64             perlfaq8          System Interaction
65             perlfaq9          Networking
66
67   Reference Manual
68           perlsyn             Perl syntax
69           perldata            Perl data structures
70           perlop              Perl operators and precedence
71           perlsub             Perl subroutines
72           perlfunc            Perl built-in functions
73             perlopentut       Perl open() tutorial
74             perlpacktut       Perl pack() and unpack() tutorial
75           perlpod             Perl plain old documentation
76           perlpodspec         Perl plain old documentation format specification
77           perlpodstyle        Perl POD style guide
78           perldiag            Perl diagnostic messages
79           perldeprecation     Perl deprecations
80           perllexwarn         Perl warnings and their control
81           perldebug           Perl debugging
82           perlvar             Perl predefined variables
83           perlre              Perl regular expressions, the rest of the story
84           perlrebackslash     Perl regular expression backslash sequences
85           perlrecharclass     Perl regular expression character classes
86           perlreref           Perl regular expressions quick reference
87           perlref             Perl references, the rest of the story
88           perlform            Perl formats
89           perlobj             Perl objects
90           perltie             Perl objects hidden behind simple variables
91             perldbmfilter     Perl DBM filters
92
93           perlipc             Perl interprocess communication
94           perlfork            Perl fork() information
95           perlnumber          Perl number semantics
96
97           perlthrtut          Perl threads tutorial
98
99           perlport            Perl portability guide
100           perllocale          Perl locale support
101           perluniintro        Perl Unicode introduction
102           perlunicode         Perl Unicode support
103           perlunicook         Perl Unicode cookbook
104           perlunifaq          Perl Unicode FAQ
105           perluniprops        Index of Unicode properties in Perl
106           perlunitut          Perl Unicode tutorial
107           perlebcdic          Considerations for running Perl on EBCDIC platforms
108
109           perlsec             Perl security
110
111           perlmod             Perl modules: how they work
112           perlmodlib          Perl modules: how to write and use
113           perlmodstyle        Perl modules: how to write modules with style
114           perlmodinstall      Perl modules: how to install from CPAN
115           perlnewmod          Perl modules: preparing a new module for distribution
116           perlpragma          Perl modules: writing a user pragma
117
118           perlutil            utilities packaged with the Perl distribution
119
120           perlfilter          Perl source filters
121
122           perldtrace          Perl's support for DTrace
123
124           perlglossary        Perl Glossary
125
126   Internals and C Language Interface
127           perlembed           Perl ways to embed perl in your C or C++ application
128           perldebguts         Perl debugging guts and tips
129           perlxstut           Perl XS tutorial
130           perlxs              Perl XS application programming interface
131           perlxstypemap       Perl XS C/Perl type conversion tools
132           perlclib            Internal replacements for standard C library functions
133           perlguts            Perl internal functions for those doing extensions
134           perlcall            Perl calling conventions from C
135           perlmroapi          Perl method resolution plugin interface
136           perlreapi           Perl regular expression plugin interface
137           perlreguts          Perl regular expression engine internals
138
139           perlapi             Perl API listing (autogenerated)
140           perlintern          Perl internal functions (autogenerated)
141           perliol             C API for Perl's implementation of IO in Layers
142           perlapio            Perl internal IO abstraction interface
143
144           perlhack            Perl hackers guide
145           perlsource          Guide to the Perl source tree
146           perlinterp          Overview of the Perl interpreter source and how it works
147           perlhacktut         Walk through the creation of a simple C code patch
148           perlhacktips        Tips for Perl core C code hacking
149           perlpolicy          Perl development policies
150           perlgit             Using git with the Perl repository
151
152   Miscellaneous
153           perlbook            Perl book information
154           perlcommunity       Perl community information
155
156           perldoc             Look up Perl documentation in Pod format
157
158           perlhist            Perl history records
159           perldelta           Perl changes since previous version
160           perl5300delta       Perl changes in version 5.30.0
161           perl5282delta       Perl changes in version 5.28.2
162           perl5281delta       Perl changes in version 5.28.1
163           perl5280delta       Perl changes in version 5.28.0
164           perl5263delta       Perl changes in version 5.26.3
165           perl5262delta       Perl changes in version 5.26.2
166           perl5261delta       Perl changes in version 5.26.1
167           perl5260delta       Perl changes in version 5.26.0
168           perl5244delta       Perl changes in version 5.24.4
169           perl5243delta       Perl changes in version 5.24.3
170           perl5242delta       Perl changes in version 5.24.2
171           perl5241delta       Perl changes in version 5.24.1
172           perl5240delta       Perl changes in version 5.24.0
173           perl5224delta       Perl changes in version 5.22.4
174           perl5223delta       Perl changes in version 5.22.3
175           perl5222delta       Perl changes in version 5.22.2
176           perl5221delta       Perl changes in version 5.22.1
177           perl5220delta       Perl changes in version 5.22.0
178           perl5203delta       Perl changes in version 5.20.3
179           perl5202delta       Perl changes in version 5.20.2
180           perl5201delta       Perl changes in version 5.20.1
181           perl5200delta       Perl changes in version 5.20.0
182           perl5184delta       Perl changes in version 5.18.4
183           perl5182delta       Perl changes in version 5.18.2
184           perl5181delta       Perl changes in version 5.18.1
185           perl5180delta       Perl changes in version 5.18.0
186           perl5163delta       Perl changes in version 5.16.3
187           perl5162delta       Perl changes in version 5.16.2
188           perl5161delta       Perl changes in version 5.16.1
189           perl5160delta       Perl changes in version 5.16.0
190           perl5144delta       Perl changes in version 5.14.4
191           perl5143delta       Perl changes in version 5.14.3
192           perl5142delta       Perl changes in version 5.14.2
193           perl5141delta       Perl changes in version 5.14.1
194           perl5140delta       Perl changes in version 5.14.0
195           perl5125delta       Perl changes in version 5.12.5
196           perl5124delta       Perl changes in version 5.12.4
197           perl5123delta       Perl changes in version 5.12.3
198           perl5122delta       Perl changes in version 5.12.2
199           perl5121delta       Perl changes in version 5.12.1
200           perl5120delta       Perl changes in version 5.12.0
201           perl5101delta       Perl changes in version 5.10.1
202           perl5100delta       Perl changes in version 5.10.0
203           perl589delta        Perl changes in version 5.8.9
204           perl588delta        Perl changes in version 5.8.8
205           perl587delta        Perl changes in version 5.8.7
206           perl586delta        Perl changes in version 5.8.6
207           perl585delta        Perl changes in version 5.8.5
208           perl584delta        Perl changes in version 5.8.4
209           perl583delta        Perl changes in version 5.8.3
210           perl582delta        Perl changes in version 5.8.2
211           perl581delta        Perl changes in version 5.8.1
212           perl58delta         Perl changes in version 5.8.0
213           perl561delta        Perl changes in version 5.6.1
214           perl56delta         Perl changes in version 5.6
215           perl5005delta       Perl changes in version 5.005
216           perl5004delta       Perl changes in version 5.004
217
218           perlexperiment      A listing of experimental features in Perl
219
220           perlartistic        Perl Artistic License
221           perlgpl             GNU General Public License
222
223   Language-Specific
224           perlcn              Perl for Simplified Chinese (in EUC-CN)
225           perljp              Perl for Japanese (in EUC-JP)
226           perlko              Perl for Korean (in EUC-KR)
227           perltw              Perl for Traditional Chinese (in Big5)
228
229   Platform-Specific
230           perlaix             Perl notes for AIX
231           perlamiga           Perl notes for AmigaOS
232           perlandroid         Perl notes for Android
233           perlbs2000          Perl notes for POSIX-BC BS2000
234           perlce              Perl notes for WinCE
235           perlcygwin          Perl notes for Cygwin
236           perldos             Perl notes for DOS
237           perlfreebsd         Perl notes for FreeBSD
238           perlhaiku           Perl notes for Haiku
239           perlhpux            Perl notes for HP-UX
240           perlhurd            Perl notes for Hurd
241           perlirix            Perl notes for Irix
242           perllinux           Perl notes for Linux
243           perlmacos           Perl notes for Mac OS (Classic)
244           perlmacosx          Perl notes for Mac OS X
245           perlnetware         Perl notes for NetWare
246           perlopenbsd         Perl notes for OpenBSD
247           perlos2             Perl notes for OS/2
248           perlos390           Perl notes for OS/390
249           perlos400           Perl notes for OS/400
250           perlplan9           Perl notes for Plan 9
251           perlqnx             Perl notes for QNX
252           perlriscos          Perl notes for RISC OS
253           perlsolaris         Perl notes for Solaris
254           perlsymbian         Perl notes for Symbian
255           perlsynology        Perl notes for Synology
256           perltru64           Perl notes for Tru64
257           perlvms             Perl notes for VMS
258           perlvos             Perl notes for Stratus VOS
259           perlwin32           Perl notes for Windows
260
261   Stubs for Deleted Documents
262           perlboot
263           perlbot
264           perlrepository
265           perltodo
266           perltooc
267           perltoot
268
269       On a Unix-like system, these documentation files will usually also be
270       available as manpages for use with the man program.
271
272       Some documentation is not available as man pages, so if a cross-
273       reference is not found by man, try it with perldoc.  Perldoc can also
274       take you directly to documentation for functions (with the -f switch).
275       See "perldoc --help" (or "perldoc perldoc" or "man perldoc") for other
276       helpful options perldoc has to offer.
277
278       In general, if something strange has gone wrong with your program and
279       you're not sure where you should look for help, try making your code
280       comply with use strict and use warnings.  These will often point out
281       exactly where the trouble is.
282

DESCRIPTION

284       Perl officially stands for Practical Extraction and Report Language,
285       except when it doesn't.
286
287       Perl was originally a language optimized for scanning arbitrary text
288       files, extracting information from those text files, and printing
289       reports based on that information.  It quickly became a good language
290       for many system management tasks. Over the years, Perl has grown into a
291       general-purpose programming language. It's widely used for everything
292       from quick "one-liners" to full-scale application development.
293
294       The language is intended to be practical (easy to use, efficient,
295       complete) rather than beautiful (tiny, elegant, minimal).  It combines
296       (in the author's opinion, anyway) some of the best features of sed,
297       awk, and sh, making it familiar and easy to use for Unix users to whip
298       up quick solutions to annoying problems.  Its general-purpose
299       programming facilities support procedural, functional, and object-
300       oriented programming paradigms, making Perl a comfortable language for
301       the long haul on major projects, whatever your bent.
302
303       Perl's roots in text processing haven't been forgotten over the years.
304       It still boasts some of the most powerful regular expressions to be
305       found anywhere, and its support for Unicode text is world-class.  It
306       handles all kinds of structured text, too, through an extensive
307       collection of extensions.  Those libraries, collected in the CPAN,
308       provide ready-made solutions to an astounding array of problems.  When
309       they haven't set the standard themselves, they steal from the best --
310       just like Perl itself.
311

AVAILABILITY

313       Perl is available for most operating systems, including virtually all
314       Unix-like platforms.  See "Supported Platforms" in perlport for a
315       listing.
316

ENVIRONMENT

318       See perlrun.
319

AUTHOR

321       Larry Wall <larry@wall.org>, with the help of oodles of other folks.
322
323       If your Perl success stories and testimonials may be of help to others
324       who wish to advocate the use of Perl in their applications, or if you
325       wish to simply express your gratitude to Larry and the Perl developers,
326       please write to perl-thanks@perl.org .
327

FILES

329        "@INC"                 locations of perl libraries
330
331       "@INC" above is a reference to the built-in variable of the same name;
332       see perlvar for more information.
333

SEE ALSO

335        http://www.perl.org/       the Perl homepage
336        http://www.perl.com/       Perl articles (O'Reilly)
337        http://www.cpan.org/       the Comprehensive Perl Archive
338        http://www.pm.org/         the Perl Mongers
339

DIAGNOSTICS

341       Using the "use strict" pragma ensures that all variables are properly
342       declared and prevents other misuses of legacy Perl features.
343
344       The "use warnings" pragma produces some lovely diagnostics. One can
345       also use the -w flag, but its use is normally discouraged, because it
346       gets applied to all executed Perl code, including that not under your
347       control.
348
349       See perldiag for explanations of all Perl's diagnostics.  The "use
350       diagnostics" pragma automatically turns Perl's normally terse warnings
351       and errors into these longer forms.
352
353       Compilation errors will tell you the line number of the error, with an
354       indication of the next token or token type that was to be examined.
355       (In a script passed to Perl via -e switches, each -e is counted as one
356       line.)
357
358       Setuid scripts have additional constraints that can produce error
359       messages such as "Insecure dependency".  See perlsec.
360
361       Did we mention that you should definitely consider using the use
362       warnings pragma?
363

BUGS

365       The behavior implied by the use warnings pragma is not mandatory.
366
367       Perl is at the mercy of your machine's definitions of various
368       operations such as type casting, atof(), and floating-point output with
369       sprintf().
370
371       If your stdio requires a seek or eof between reads and writes on a
372       particular stream, so does Perl.  (This doesn't apply to sysread() and
373       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
377       given variable name may not be longer than 251 characters.  Line
378       numbers displayed by diagnostics are internally stored as short
379       integers, so they are limited to a maximum of 65535 (higher numbers
380       usually being affected by wraparound).
381
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,
384       or by "perl -V") to perlbug@perl.org .  If you've succeeded in
385       compiling perl, the perlbug script in the utils/ subdirectory can be
386       used to help mail in a bug report.
387
388       Perl actually stands for Pathologically Eclectic Rubbish Lister, but
389       don't tell anyone I said that.
390

NOTES

392       The Perl motto is "There's more than one way to do it."  Divining how
393       many more is left as an exercise to the reader.
394
395       The three principal virtues of a programmer are Laziness, Impatience,
396       and Hubris.  See the Camel Book for why.
397
398
399
400perl v5.30.1                      2019-11-29                           PERL(1)
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