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 perlfaq Perl frequently asked questions
24 perltoc Perl documentation table of contents
26 perldata Perl data structures
28 perlop Perl operators and precedence
29 perlre Perl regular expressions
30 perlrun Perl execution and options
31 perlfunc Perl builtin functions
32 perlvar Perl predefined variables
33 perlsub Perl subroutines
34 perlmod Perl modules: how they work
35 perlmodlib Perl modules: how to write and use
37 perllocale Perl locale support
39 perlref Perl references
40 perldsc Perl data structures intro
41 perllol Perl data structures: lists of lists
42 perltoot Perl OO tutorial
44 perltie Perl objects hidden behind simple variables
45 perlbot Perl OO tricks and examples
46 perlipc Perl interprocess communication
48 perldebug Perl debugging
49 perldiag Perl diagnostic messages
51 perltrap Perl traps for the unwary
52 perlstyle Perl style guide
54 perlpod Perl plain old documentation
55 perlbook Perl book information
57 perlembed Perl ways to embed perl in your C or C++ application
58 perlapio Perl internal IO abstraction interface
59 perlxs Perl XS application programming interface
60 perlxstut Perl XS tutorial
61 perlguts Perl internal functions for those doing extensions
62 perlcall Perl calling conventions from C
64 perlhist Perl history records
66 (If you're intending to read these straight through for the first time,
67 the suggested order will tend to reduce the number of forward references.)
69 By default, all of the above manpages are installed in the
70 F</usr/local/man/> directory.
72 Extensive additional documentation for Perl modules is available. The
73 default configuration for perl will place this additional documentation
74 in the F</usr/local/lib/perl5/man> directory (or else in the F<man>
75 subdirectory of the Perl library directory). Some of this additional
76 documentation is distributed standard with Perl, but you'll also find
77 documentation for third-party modules there.
79 You should be able to view Perl's documentation with your man(1)
80 program by including the proper directories in the appropriate start-up
81 files, or in the MANPATH environment variable. To find out where the
82 configuration has installed the manpages, type:
86 If the directories have a common stem, such as F</usr/local/man/man1>
87 and F</usr/local/man/man3>, you need only to add that stem
88 (F</usr/local/man>) to your man(1) configuration files or your MANPATH
89 environment variable. If they do not share a stem, you'll have to add
92 If that doesn't work for some reason, you can still use the
93 supplied F<perldoc> script to view module information. You might
94 also look into getting a replacement man program.
96 If something strange has gone wrong with your program and you're not
97 sure where you should look for help, try the B<-w> switch first. It
98 will often point out exactly where the trouble is.
102 Perl is a language optimized for scanning arbitrary
103 text files, extracting information from those text files, and printing
104 reports based on that information. It's also a good language for many
105 system management tasks. The language is intended to be practical
106 (easy to use, efficient, complete) rather than beautiful (tiny,
109 Perl combines (in the author's opinion, anyway) some of the best
110 features of C, B<sed>, B<awk>, and B<sh>, so people familiar with
111 those languages should have little difficulty with it. (Language
112 historians will also note some vestiges of B<csh>, Pascal, and even
113 BASIC-PLUS.) Expression syntax corresponds quite closely to C
114 expression syntax. Unlike most Unix utilities, Perl does not
115 arbitrarily limit the size of your data--if you've got the memory,
116 Perl can slurp in your whole file as a single string. Recursion is of
117 unlimited depth. And the tables used by hashes (previously called
118 "associative arrays") grow as necessary to prevent degraded
119 performance. Perl uses sophisticated pattern matching techniques to
120 scan large amounts of data very quickly. Although optimized for
121 scanning text, Perl can also deal with binary data, and can make dbm
122 files look like hashes. Setuid Perl scripts are safer than C programs
123 through a dataflow tracing mechanism which prevents many stupid
126 If you have a problem that would ordinarily use B<sed> or B<awk> or
127 B<sh>, but it exceeds their capabilities or must run a little faster,
128 and you don't want to write the silly thing in C, then Perl may be for
129 you. There are also translators to turn your B<sed> and B<awk>
130 scripts into Perl scripts.
132 But wait, there's more...
134 Perl version 5 is nearly a complete rewrite, and provides
135 the following additional benefits:
139 =item * Many usability enhancements
141 It is now possible to write much more readable Perl code (even within
142 regular expressions). Formerly cryptic variable names can be replaced
143 by mnemonic identifiers. Error messages are more informative, and the
144 optional warnings will catch many of the mistakes a novice might make.
145 This cannot be stressed enough. Whenever you get mysterious behavior,
146 try the B<-w> switch!!! Whenever you don't get mysterious behavior,
147 try using B<-w> anyway.
149 =item * Simplified grammar
151 The new yacc grammar is one half the size of the old one. Many of the
152 arbitrary grammar rules have been regularized. The number of reserved
153 words has been cut by 2/3. Despite this, nearly all old Perl scripts
154 will continue to work unchanged.
156 =item * Lexical scoping
158 Perl variables may now be declared within a lexical scope, like "auto"
159 variables in C. Not only is this more efficient, but it contributes
160 to better privacy for "programming in the large". Anonymous
161 subroutines exhibit deep binding of lexical variables (closures).
163 =item * Arbitrarily nested data structures
165 Any scalar value, including any array element, may now contain a
166 reference to any other variable or subroutine. You can easily create
167 anonymous variables and subroutines. Perl manages your reference
170 =item * Modularity and reusability
172 The Perl library is now defined in terms of modules which can be easily
173 shared among various packages. A package may choose to import all or a
174 portion of a module's published interface. Pragmas (that is, compiler
175 directives) are defined and used by the same mechanism.
177 =item * Object-oriented programming
179 A package can function as a class. Dynamic multiple inheritance and
180 virtual methods are supported in a straightforward manner and with very
181 little new syntax. Filehandles may now be treated as objects.
183 =item * Embeddable and Extensible
185 Perl may now be embedded easily in your C or C++ application, and can
186 either call or be called by your routines through a documented
187 interface. The XS preprocessor is provided to make it easy to glue
188 your C or C++ routines into Perl. Dynamic loading of modules is
189 supported, and Perl itself can be made into a dynamic library.
191 =item * POSIX compliant
193 A major new module is the POSIX module, which provides access to all
194 available POSIX routines and definitions, via object classes where
197 =item * Package constructors and destructors
199 The new BEGIN and END blocks provide means to capture control as
200 a package is being compiled, and after the program exits. As a
201 degenerate case they work just like awk's BEGIN and END when you
202 use the B<-p> or B<-n> switches.
204 =item * Multiple simultaneous DBM implementations
206 A Perl program may now access DBM, NDBM, SDBM, GDBM, and Berkeley DB
207 files from the same script simultaneously. In fact, the old dbmopen
208 interface has been generalized to allow any variable to be tied
209 to an object class which defines its access methods.
211 =item * Subroutine definitions may now be autoloaded
213 In fact, the AUTOLOAD mechanism also allows you to define any arbitrary
214 semantics for undefined subroutine calls. It's not for just autoloading.
216 =item * Regular expression enhancements
218 You can now specify nongreedy quantifiers. You can now do grouping
219 without creating a backreference. You can now write regular expressions
220 with embedded whitespace and comments for readability. A consistent
221 extensibility mechanism has been added that is upwardly compatible with
222 all old regular expressions.
224 =item * Innumerable Unbundled Modules
226 The Comprehensive Perl Archive Network described in L<perlmodlib>
227 contains hundreds of plug-and-play modules full of reusable code.
228 See F<http://www.perl.com/CPAN> for a site near you.
230 =item * Compilability
232 While not yet in full production mode, a working perl-to-C compiler
233 does exist. It can generate portable byte code, simple C, or
238 Okay, that's I<definitely> enough hype.
246 Larry Wall <F<larry@wall.org>>, with the help of oodles of other folks.
248 If your Perl success stories and testimonials may be of help to others
249 who wish to advocate the use of Perl in their applications,
250 or if you wish to simply express your gratitude to Larry and the
251 Perl developers, please write to <F<perl-thanks@perl.org>>.
255 "/tmp/perl-e$$" temporary file for -e commands
256 "@INC" locations of perl libraries
260 a2p awk to perl translator
262 s2p sed to perl translator
266 The B<-w> switch produces some lovely diagnostics.
268 See L<perldiag> for explanations of all Perl's diagnostics.
270 Compilation errors will tell you the line number of the error, with an
271 indication of the next token or token type that was to be examined.
272 (In the case of a script passed to Perl via B<-e> switches, each
273 B<-e> is counted as one line.)
275 Setuid scripts have additional constraints that can produce error
276 messages such as "Insecure dependency". See L<perlsec>.
278 Did we mention that you should definitely consider using the B<-w>
283 The B<-w> switch is not mandatory.
285 Perl is at the mercy of your machine's definitions of various
286 operations such as type casting, atof(), and floating-point
287 output with sprintf().
289 If your stdio requires a seek or eof between reads and writes on a
290 particular stream, so does Perl. (This doesn't apply to sysread()
293 While none of the built-in data types have any arbitrary size limits
294 (apart from memory size), there are still a few arbitrary limits: a
295 given variable name may not be longer than 255 characters, and no
296 component of your PATH may be longer than 255 if you use B<-S>. A regular
297 expression may not compile to more than 32767 bytes internally.
299 You may mail your bug reports (be sure to include full configuration
300 information as output by the myconfig program in the perl source tree,
301 or by C<perl -V>) to <F<perlbug@perl.com>>.
302 If you've succeeded in compiling perl, the perlbug script in the utils/
303 subdirectory can be used to help mail in a bug report.
305 Perl actually stands for Pathologically Eclectic Rubbish Lister, but
306 don't tell anyone I said that.
310 The Perl motto is "There's more than one way to do it." Divining
311 how many more is left as an exercise to the reader.
313 The three principal virtues of a programmer are Laziness,
314 Impatience, and Hubris. See the Camel Book for why.