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
54 perldebug Perl debugging
55 perldiag Perl diagnostic messages
57 perltrap Perl traps for the unwary
58 perlport Perl portability guide
59 perlstyle Perl style guide
61 perlpod Perl plain old documentation
62 perlbook Perl book information
64 perlembed Perl ways to embed perl in your C or C++ application
65 perlapio Perl internal IO abstraction interface
66 perlxs Perl XS application programming interface
67 perlxstut Perl XS tutorial
68 perlguts Perl internal functions for those doing extensions
69 perlcall Perl calling conventions from C
71 perltodo Perl things to do
72 perlhist Perl history records
74 (If you're intending to read these straight through for the first time,
75 the suggested order will tend to reduce the number of forward references.)
77 By default, all of the above manpages are installed in the
78 F</usr/local/man/> directory.
80 Extensive additional documentation for Perl modules is available. The
81 default configuration for perl will place this additional documentation
82 in the F</usr/local/lib/perl5/man> directory (or else in the F<man>
83 subdirectory of the Perl library directory). Some of this additional
84 documentation is distributed standard with Perl, but you'll also find
85 documentation for third-party modules there.
87 You should be able to view Perl's documentation with your man(1)
88 program by including the proper directories in the appropriate start-up
89 files, or in the MANPATH environment variable. To find out where the
90 configuration has installed the manpages, type:
94 If the directories have a common stem, such as F</usr/local/man/man1>
95 and F</usr/local/man/man3>, you need only to add that stem
96 (F</usr/local/man>) to your man(1) configuration files or your MANPATH
97 environment variable. If they do not share a stem, you'll have to add
100 If that doesn't work for some reason, you can still use the
101 supplied F<perldoc> script to view module information. You might
102 also look into getting a replacement man program.
104 If something strange has gone wrong with your program and you're not
105 sure where you should look for help, try the B<-w> switch first. It
106 will often point out exactly where the trouble is.
110 Perl is a language optimized for scanning arbitrary
111 text files, extracting information from those text files, and printing
112 reports based on that information. It's also a good language for many
113 system management tasks. The language is intended to be practical
114 (easy to use, efficient, complete) rather than beautiful (tiny,
117 Perl combines (in the author's opinion, anyway) some of the best
118 features of C, B<sed>, B<awk>, and B<sh>, so people familiar with
119 those languages should have little difficulty with it. (Language
120 historians will also note some vestiges of B<csh>, Pascal, and even
121 BASIC-PLUS.) Expression syntax corresponds quite closely to C
122 expression syntax. Unlike most Unix utilities, Perl does not
123 arbitrarily limit the size of your data--if you've got the memory,
124 Perl can slurp in your whole file as a single string. Recursion is of
125 unlimited depth. And the tables used by hashes (sometimes called
126 "associative arrays") grow as necessary to prevent degraded
127 performance. Perl can use sophisticated pattern matching techniques to
128 scan large amounts of data very quickly. Although optimized for
129 scanning text, Perl can also deal with binary data, and can make dbm
130 files look like hashes. Setuid Perl scripts are safer than C programs
131 through a dataflow tracing mechanism which prevents many stupid
134 If you have a problem that would ordinarily use B<sed> or B<awk> or
135 B<sh>, but it exceeds their capabilities or must run a little faster,
136 and you don't want to write the silly thing in C, then Perl may be for
137 you. There are also translators to turn your B<sed> and B<awk>
138 scripts into Perl scripts.
140 But wait, there's more...
142 Perl version 5 is nearly a complete rewrite, and provides
143 the following additional benefits:
147 =item * Many usability enhancements
149 It is now possible to write much more readable Perl code (even within
150 regular expressions). Formerly cryptic variable names can be replaced
151 by mnemonic identifiers. Error messages are more informative, and the
152 optional warnings will catch many of the mistakes a novice might make.
153 This cannot be stressed enough. Whenever you get mysterious behavior,
154 try the B<-w> switch!!! Whenever you don't get mysterious behavior,
155 try using B<-w> anyway.
157 =item * Simplified grammar
159 The new yacc grammar is one half the size of the old one. Many of the
160 arbitrary grammar rules have been regularized. The number of reserved
161 words has been cut by 2/3. Despite this, nearly all old Perl scripts
162 will continue to work unchanged.
164 =item * Lexical scoping
166 Perl variables may now be declared within a lexical scope, like "auto"
167 variables in C. Not only is this more efficient, but it contributes
168 to better privacy for "programming in the large". Anonymous
169 subroutines exhibit deep binding of lexical variables (closures).
171 =item * Arbitrarily nested data structures
173 Any scalar value, including any array element, may now contain a
174 reference to any other variable or subroutine. You can easily create
175 anonymous variables and subroutines. Perl manages your reference
178 =item * Modularity and reusability
180 The Perl library is now defined in terms of modules which can be easily
181 shared among various packages. A package may choose to import all or a
182 portion of a module's published interface. Pragmas (that is, compiler
183 directives) are defined and used by the same mechanism.
185 =item * Object-oriented programming
187 A package can function as a class. Dynamic multiple inheritance and
188 virtual methods are supported in a straightforward manner and with very
189 little new syntax. Filehandles may now be treated as objects.
191 =item * Embeddable and Extensible
193 Perl may now be embedded easily in your C or C++ application, and can
194 either call or be called by your routines through a documented
195 interface. The XS preprocessor is provided to make it easy to glue
196 your C or C++ routines into Perl. Dynamic loading of modules is
197 supported, and Perl itself can be made into a dynamic library.
199 =item * POSIX compliant
201 A major new module is the POSIX module, which provides access to all
202 available POSIX routines and definitions, via object classes where
205 =item * Package constructors and destructors
207 The new BEGIN and END blocks provide means to capture control as
208 a package is being compiled, and after the program exits. As a
209 degenerate case they work just like awk's BEGIN and END when you
210 use the B<-p> or B<-n> switches.
212 =item * Multiple simultaneous DBM implementations
214 A Perl program may now access DBM, NDBM, SDBM, GDBM, and Berkeley DB
215 files from the same script simultaneously. In fact, the old dbmopen
216 interface has been generalized to allow any variable to be tied
217 to an object class which defines its access methods.
219 =item * Subroutine definitions may now be autoloaded
221 In fact, the AUTOLOAD mechanism also allows you to define any arbitrary
222 semantics for undefined subroutine calls. It's not for just autoloading.
224 =item * Regular expression enhancements
226 You can now specify nongreedy quantifiers. You can now do grouping
227 without creating a backreference. You can now write regular expressions
228 with embedded whitespace and comments for readability. A consistent
229 extensibility mechanism has been added that is upwardly compatible with
230 all old regular expressions.
232 =item * Innumerable Unbundled Modules
234 The Comprehensive Perl Archive Network described in L<perlmodlib>
235 contains hundreds of plug-and-play modules full of reusable code.
236 See F<http://www.perl.com/CPAN> for a site near you.
238 =item * Compilability
240 While not yet in full production mode, a working perl-to-C compiler
241 does exist. It can generate portable byte code, simple C, or
246 Okay, that's I<definitely> enough hype.
250 Perl is available for the vast majority of operating system platforms,
251 including most Unix-like platforms. The following situation is as of
252 February 1999 and Perl 5.005_03.
254 The following platforms are able to build Perl from the standard
255 source code distribution available at
256 F<http://www.perl.com/CPAN/src/index.html>
263 Digital UNIX NextSTEP UNICOS
264 DOS DJGPP 1) OpenBSD VMS
265 DYNIX/ptx OpenSTEP Windows 3.1 1)
266 FreeBSD OS/2 Windows 95 1) 3)
267 HP-UX OS390 2) Windows 98 1) 3)
268 Hurd PowerUX Windows NT 1) 3)
271 1) in DOS mode either the DOS or OS/2 ports can be used
272 2) formerly known as MVS
273 3) compilers: Borland, Cygwin32, Mingw32 EGCS/GCC, VC++
275 The following platforms have been known to build Perl from the source
276 but for the Perl release 5.005_03 we haven't been able to verify them,
277 either because the hardware/software platforms are rather rare or
278 because we don't have an active champion on these platforms.
281 AmigaOS GENIX RISC/os
282 ConvexOS Greenhills Stellar
284 DC/OSx MachTen 68k TI1500
285 DDE SMES MiNT TitanOS
286 DomainOS MPC UNICOS/mk
287 DOS EMX NEWS-OS Unisys Dynix
292 The following platforms are planned to be supported in the standard
293 source distribution of the Perl release 5.006 but are not
294 supported in the Perl release 5.005_03:
299 The following platforms have their own source code distributions and
300 binaries available via F<http://www.perl.com/CPAN/ports/index.html>.
306 Tandem Guardian 5.004
308 The following platforms have only binaries available via
309 F<http://www.perl.com/CPAN/ports/index.html>.
324 Larry Wall <F<larry@wall.org>>, with the help of oodles of other folks.
326 If your Perl success stories and testimonials may be of help to others
327 who wish to advocate the use of Perl in their applications,
328 or if you wish to simply express your gratitude to Larry and the
329 Perl developers, please write to <F<perl-thanks@perl.org>>.
333 "@INC" locations of perl libraries
337 a2p awk to perl translator
339 s2p sed to perl translator
343 The B<-w> switch produces some lovely diagnostics.
345 See L<perldiag> for explanations of all Perl's diagnostics. The C<use
346 diagnostics> pragma automatically turns Perl's normally terse warnings
347 and errors into these longer forms.
349 Compilation errors will tell you the line number of the error, with an
350 indication of the next token or token type that was to be examined.
351 (In the case of a script passed to Perl via B<-e> switches, each
352 B<-e> is counted as one line.)
354 Setuid scripts have additional constraints that can produce error
355 messages such as "Insecure dependency". See L<perlsec>.
357 Did we mention that you should definitely consider using the B<-w>
362 The B<-w> switch is not mandatory.
364 Perl is at the mercy of your machine's definitions of various
365 operations such as type casting, atof(), and floating-point
366 output with sprintf().
368 If your stdio requires a seek or eof between reads and writes on a
369 particular stream, so does Perl. (This doesn't apply to sysread()
372 While none of the built-in data types have any arbitrary size limits
373 (apart from memory size), there are still a few arbitrary limits: a
374 given variable name may not be longer than 251 characters. Line numbers
375 displayed by diagnostics are internally stored as short integers,
376 so they are limited to a maximum of 65535 (higher numbers usually being
377 affected by wraparound).
379 You may mail your bug reports (be sure to include full configuration
380 information as output by the myconfig program in the perl source tree,
381 or by C<perl -V>) to <F<perlbug@perl.com>>.
382 If you've succeeded in compiling perl, the perlbug script in the utils/
383 subdirectory can be used to help mail in a bug report.
385 Perl actually stands for Pathologically Eclectic Rubbish Lister, but
386 don't tell anyone I said that.
390 The Perl motto is "There's more than one way to do it." Divining
391 how many more is left as an exercise to the reader.
393 The three principal virtues of a programmer are Laziness,
394 Impatience, and Hubris. See the Camel Book for why.