3 perl - Practical Extraction and Report Language
7 B<perl> S<[ B<-sTuU> ]>
8 S<[ B<-hv> ] [ B<-V>[:I<configvar>] ]>
9 S<[ B<-cw> ] [ B<-d>[:I<debugger>] ] [ B<-D>[I<number/list>] ]>
10 S<[ B<-pna> ] [ B<-F>I<pattern> ] [ B<-l>[I<octal>] ] [ B<-0>[I<octal>] ]>
11 S<[ B<-I>I<dir> ] [ B<-m>[B<->]I<module> ] [ B<-M>[B<->]I<'module...'> ]>
15 S<[ B<-i>[I<extension>] ]>
16 S<[ B<-e> I<'command'> ] [ B<--> ] [ I<programfile> ] [ I<argument> ]...>
18 For ease of access, the Perl manual has been split up into a number
21 perl Perl overview (this section)
22 perldelta Perl changes since previous version
23 perl5005delta Perl changes in version 5.005
24 perl5004delta Perl changes in version 5.004
25 perlfaq Perl frequently asked questions
26 perltoc Perl documentation table of contents
28 perldata Perl data structures
30 perlop Perl operators and precedence
31 perlre Perl regular expressions
32 perlrun Perl execution and options
33 perlfunc Perl builtin functions
34 perlopentut Perl open() tutorial
35 perlvar Perl predefined variables
36 perlsub Perl subroutines
37 perlmod Perl modules: how they work
38 perlmodlib Perl modules: how to write and use
39 perlmodinstall Perl modules: how to install from CPAN
41 perllocale Perl locale support
43 perlref Perl references
44 perlreftut Perl references short introduction
45 perldsc Perl data structures intro
46 perllol Perl data structures: lists of lists
47 perltoot Perl OO tutorial
49 perltie Perl objects hidden behind simple variables
50 perlbot Perl OO tricks and examples
51 perlipc Perl interprocess communication
52 perlthrtut Perl threads tutorial
53 perldbmfilter Perl DBM Filters
55 perldebug Perl debugging
56 perldiag Perl diagnostic messages
58 perltrap Perl traps for the unwary
59 perlport Perl portability guide
60 perlstyle Perl style guide
62 perlpod Perl plain old documentation
63 perlbook Perl book information
65 perlembed Perl ways to embed perl in your C or C++ application
66 perlapio Perl internal IO abstraction interface
67 perlxs Perl XS application programming interface
68 perlxstut Perl XS tutorial
69 perlguts Perl internal functions for those doing extensions
70 perlcall Perl calling conventions from C
72 perltodo Perl things to do
73 perlhist Perl history records
75 (If you're intending to read these straight through for the first time,
76 the suggested order will tend to reduce the number of forward references.)
78 By default, all of the above manpages are installed in the
79 F</usr/local/man/> directory.
81 Extensive additional documentation for Perl modules is available. The
82 default configuration for perl will place this additional documentation
83 in the F</usr/local/lib/perl5/man> directory (or else in the F<man>
84 subdirectory of the Perl library directory). Some of this additional
85 documentation is distributed standard with Perl, but you'll also find
86 documentation for third-party modules there.
88 You should be able to view Perl's documentation with your man(1)
89 program by including the proper directories in the appropriate start-up
90 files, or in the MANPATH environment variable. To find out where the
91 configuration has installed the manpages, type:
95 If the directories have a common stem, such as F</usr/local/man/man1>
96 and F</usr/local/man/man3>, you need only to add that stem
97 (F</usr/local/man>) to your man(1) configuration files or your MANPATH
98 environment variable. If they do not share a stem, you'll have to add
101 If that doesn't work for some reason, you can still use the
102 supplied F<perldoc> script to view module information. You might
103 also look into getting a replacement man program.
105 If something strange has gone wrong with your program and you're not
106 sure where you should look for help, try the B<-w> switch first. It
107 will often point out exactly where the trouble is.
111 Perl is a language optimized for scanning arbitrary
112 text files, extracting information from those text files, and printing
113 reports based on that information. It's also a good language for many
114 system management tasks. The language is intended to be practical
115 (easy to use, efficient, complete) rather than beautiful (tiny,
118 Perl combines (in the author's opinion, anyway) some of the best
119 features of C, B<sed>, B<awk>, and B<sh>, so people familiar with
120 those languages should have little difficulty with it. (Language
121 historians will also note some vestiges of B<csh>, Pascal, and even
122 BASIC-PLUS.) Expression syntax corresponds quite closely to C
123 expression syntax. Unlike most Unix utilities, Perl does not
124 arbitrarily limit the size of your data--if you've got the memory,
125 Perl can slurp in your whole file as a single string. Recursion is of
126 unlimited depth. And the tables used by hashes (sometimes called
127 "associative arrays") grow as necessary to prevent degraded
128 performance. Perl can use sophisticated pattern matching techniques to
129 scan large amounts of data very quickly. Although optimized for
130 scanning text, Perl can also deal with binary data, and can make dbm
131 files look like hashes. Setuid Perl scripts are safer than C programs
132 through a dataflow tracing mechanism which prevents many stupid
135 If you have a problem that would ordinarily use B<sed> or B<awk> or
136 B<sh>, but it exceeds their capabilities or must run a little faster,
137 and you don't want to write the silly thing in C, then Perl may be for
138 you. There are also translators to turn your B<sed> and B<awk>
139 scripts into Perl scripts.
141 But wait, there's more...
143 Perl version 5 is nearly a complete rewrite, and provides
144 the following additional benefits:
148 =item * Many usability enhancements
150 It is now possible to write much more readable Perl code (even within
151 regular expressions). Formerly cryptic variable names can be replaced
152 by mnemonic identifiers. Error messages are more informative, and the
153 optional warnings will catch many of the mistakes a novice might make.
154 This cannot be stressed enough. Whenever you get mysterious behavior,
155 try the B<-w> switch!!! Whenever you don't get mysterious behavior,
156 try using B<-w> anyway.
158 =item * Simplified grammar
160 The new yacc grammar is one half the size of the old one. Many of the
161 arbitrary grammar rules have been regularized. The number of reserved
162 words has been cut by 2/3. Despite this, nearly all old Perl scripts
163 will continue to work unchanged.
165 =item * Lexical scoping
167 Perl variables may now be declared within a lexical scope, like "auto"
168 variables in C. Not only is this more efficient, but it contributes
169 to better privacy for "programming in the large". Anonymous
170 subroutines exhibit deep binding of lexical variables (closures).
172 =item * Arbitrarily nested data structures
174 Any scalar value, including any array element, may now contain a
175 reference to any other variable or subroutine. You can easily create
176 anonymous variables and subroutines. Perl manages your reference
179 =item * Modularity and reusability
181 The Perl library is now defined in terms of modules which can be easily
182 shared among various packages. A package may choose to import all or a
183 portion of a module's published interface. Pragmas (that is, compiler
184 directives) are defined and used by the same mechanism.
186 =item * Object-oriented programming
188 A package can function as a class. Dynamic multiple inheritance and
189 virtual methods are supported in a straightforward manner and with very
190 little new syntax. Filehandles may now be treated as objects.
192 =item * Embeddable and Extensible
194 Perl may now be embedded easily in your C or C++ application, and can
195 either call or be called by your routines through a documented
196 interface. The XS preprocessor is provided to make it easy to glue
197 your C or C++ routines into Perl. Dynamic loading of modules is
198 supported, and Perl itself can be made into a dynamic library.
200 =item * POSIX compliant
202 A major new module is the POSIX module, which provides access to all
203 available POSIX routines and definitions, via object classes where
206 =item * Package constructors and destructors
208 The new BEGIN and END blocks provide means to capture control as
209 a package is being compiled, and after the program exits. As a
210 degenerate case they work just like awk's BEGIN and END when you
211 use the B<-p> or B<-n> switches.
213 =item * Multiple simultaneous DBM implementations
215 A Perl program may now access DBM, NDBM, SDBM, GDBM, and Berkeley DB
216 files from the same script simultaneously. In fact, the old dbmopen
217 interface has been generalized to allow any variable to be tied
218 to an object class which defines its access methods.
220 =item * Subroutine definitions may now be autoloaded
222 In fact, the AUTOLOAD mechanism also allows you to define any arbitrary
223 semantics for undefined subroutine calls. It's not for just autoloading.
225 =item * Regular expression enhancements
227 You can now specify nongreedy quantifiers. You can now do grouping
228 without creating a backreference. You can now write regular expressions
229 with embedded whitespace and comments for readability. A consistent
230 extensibility mechanism has been added that is upwardly compatible with
231 all old regular expressions.
233 =item * Innumerable Unbundled Modules
235 The Comprehensive Perl Archive Network described in L<perlmodlib>
236 contains hundreds of plug-and-play modules full of reusable code.
237 See F<http://www.perl.com/CPAN> for a site near you.
239 =item * Compilability
241 While not yet in full production mode, a working perl-to-C compiler
242 does exist. It can generate portable byte code, simple C, or
247 Okay, that's I<definitely> enough hype.
251 Perl is available for the vast majority of operating system platforms,
252 including most Unix-like platforms. The following situation is as of
253 February 1999 and Perl 5.005_03.
255 The following platforms are able to build Perl from the standard
256 source code distribution available at
257 F<http://www.perl.com/CPAN/src/index.html>
259 AIX Linux SCO ODT/OSR
263 DG/UX NextSTEP Tru64 UNIX 3)
264 DomainOS OpenBSD Ultrix
265 DOS DJGPP 1) OpenSTEP UNICOS
268 HP-UX PowerMAX Windows 3.1 1)
269 Hurd QNX Windows 95 1) 4)
270 IRIX Windows 98 1) 4)
273 1) in DOS mode either the DOS or OS/2 ports can be used
274 2) formerly known as MVS
275 3) formerly known as Digital UNIX and before that DEC OSF/1
276 4) compilers: Borland, Cygwin32, Mingw32 EGCS/GCC, VC++
278 The following platforms have been known to build Perl from the source
279 but for the Perl release 5.005_03 we haven't been able to verify them,
280 either because the hardware/software platforms are rather rare or
281 because we don't have an active champion on these platforms, or both.
284 AmigaOS GENIX PowerUX
285 ConvexOS Greenhills RISC/os
287 DC/OSx MachTen 68k SVR2
290 Dynix NEWS-OS UNICOS/mk
291 EP/IX Opus Unisys Dynix
294 The following platforms are planned to be supported in the standard
295 source code distribution of the Perl release 5.006 but are not
296 supported in the Perl release 5.005_03:
303 The following platforms have their own source code distributions and
304 binaries available via F<http://www.perl.com/CPAN/ports/index.html>.
311 Tandem Guardian 5.004
313 The following platforms have only binaries available via
314 F<http://www.perl.com/CPAN/ports/index.html>.
318 Acorn RISCOS 5.005_02
328 Larry Wall <F<larry@wall.org>>, with the help of oodles of other folks.
330 If your Perl success stories and testimonials may be of help to others
331 who wish to advocate the use of Perl in their applications,
332 or if you wish to simply express your gratitude to Larry and the
333 Perl developers, please write to <F<perl-thanks@perl.org>>.
337 "@INC" locations of perl libraries
341 a2p awk to perl translator
343 s2p sed to perl translator
347 The B<-w> switch produces some lovely diagnostics.
349 See L<perldiag> for explanations of all Perl's diagnostics. The C<use
350 diagnostics> pragma automatically turns Perl's normally terse warnings
351 and errors into these longer forms.
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 the case of a script passed to Perl via B<-e> switches, each
356 B<-e> is counted as one line.)
358 Setuid scripts have additional constraints that can produce error
359 messages such as "Insecure dependency". See L<perlsec>.
361 Did we mention that you should definitely consider using the B<-w>
366 The B<-w> switch is not mandatory.
368 Perl is at the mercy of your machine's definitions of various
369 operations such as type casting, atof(), and floating-point
370 output with sprintf().
372 If your stdio requires a seek or eof between reads and writes on a
373 particular stream, so does Perl. (This doesn't apply to sysread()
376 While none of the built-in data types have any arbitrary size limits
377 (apart from memory size), there are still a few arbitrary limits: a
378 given variable name may not be longer than 251 characters. Line numbers
379 displayed by diagnostics are internally stored as short integers,
380 so they are limited to a maximum of 65535 (higher numbers usually being
381 affected by wraparound).
383 You may mail your bug reports (be sure to include full configuration
384 information as output by the myconfig program in the perl source tree,
385 or by C<perl -V>) to <F<perlbug@perl.com>>.
386 If you've succeeded in compiling perl, the perlbug script in the utils/
387 subdirectory can be used to help mail in a bug report.
389 Perl actually stands for Pathologically Eclectic Rubbish Lister, but
390 don't tell anyone I said that.
394 The Perl motto is "There's more than one way to do it." Divining
395 how many more is left as an exercise to the reader.
397 The three principal virtues of a programmer are Laziness,
398 Impatience, and Hubris. See the Camel Book for why.