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