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
36 perlmodinstall Perl modules: how to install from CPAN
38 perllocale Perl locale support
40 perlref Perl references
41 perldsc Perl data structures intro
42 perllol Perl data structures: lists of lists
43 perltoot Perl OO tutorial
45 perltie Perl objects hidden behind simple variables
46 perlbot Perl OO tricks and examples
47 perlipc Perl interprocess communication
49 perldebug Perl debugging
50 perldiag Perl diagnostic messages
52 perltrap Perl traps for the unwary
53 perlport Perl portability guide
54 perlstyle Perl style guide
56 perlpod Perl plain old documentation
57 perlbook Perl book information
59 perlembed Perl ways to embed perl in your C or C++ application
60 perlapio Perl internal IO abstraction interface
61 perlxs Perl XS application programming interface
62 perlxstut Perl XS tutorial
63 perlguts Perl internal functions for those doing extensions
64 perlcall Perl calling conventions from C
66 perlhist Perl history records
68 (If you're intending to read these straight through for the first time,
69 the suggested order will tend to reduce the number of forward references.)
71 By default, all of the above manpages are installed in the
72 F</usr/local/man/> directory.
74 Extensive additional documentation for Perl modules is available. The
75 default configuration for perl will place this additional documentation
76 in the F</usr/local/lib/perl5/man> directory (or else in the F<man>
77 subdirectory of the Perl library directory). Some of this additional
78 documentation is distributed standard with Perl, but you'll also find
79 documentation for third-party modules there.
81 You should be able to view Perl's documentation with your man(1)
82 program by including the proper directories in the appropriate start-up
83 files, or in the MANPATH environment variable. To find out where the
84 configuration has installed the manpages, type:
88 If the directories have a common stem, such as F</usr/local/man/man1>
89 and F</usr/local/man/man3>, you need only to add that stem
90 (F</usr/local/man>) to your man(1) configuration files or your MANPATH
91 environment variable. If they do not share a stem, you'll have to add
94 If that doesn't work for some reason, you can still use the
95 supplied F<perldoc> script to view module information. You might
96 also look into getting a replacement man program.
98 If something strange has gone wrong with your program and you're not
99 sure where you should look for help, try the B<-w> switch first. It
100 will often point out exactly where the trouble is.
104 Perl is a language optimized for scanning arbitrary
105 text files, extracting information from those text files, and printing
106 reports based on that information. It's also a good language for many
107 system management tasks. The language is intended to be practical
108 (easy to use, efficient, complete) rather than beautiful (tiny,
111 Perl combines (in the author's opinion, anyway) some of the best
112 features of C, B<sed>, B<awk>, and B<sh>, so people familiar with
113 those languages should have little difficulty with it. (Language
114 historians will also note some vestiges of B<csh>, Pascal, and even
115 BASIC-PLUS.) Expression syntax corresponds quite closely to C
116 expression syntax. Unlike most Unix utilities, Perl does not
117 arbitrarily limit the size of your data--if you've got the memory,
118 Perl can slurp in your whole file as a single string. Recursion is of
119 unlimited depth. And the tables used by hashes (previously called
120 "associative arrays") grow as necessary to prevent degraded
121 performance. Perl uses sophisticated pattern matching techniques to
122 scan large amounts of data very quickly. Although optimized for
123 scanning text, Perl can also deal with binary data, and can make dbm
124 files look like hashes. Setuid Perl scripts are safer than C programs
125 through a dataflow tracing mechanism which prevents many stupid
128 If you have a problem that would ordinarily use B<sed> or B<awk> or
129 B<sh>, but it exceeds their capabilities or must run a little faster,
130 and you don't want to write the silly thing in C, then Perl may be for
131 you. There are also translators to turn your B<sed> and B<awk>
132 scripts into Perl scripts.
134 But wait, there's more...
136 Perl version 5 is nearly a complete rewrite, and provides
137 the following additional benefits:
141 =item * Many usability enhancements
143 It is now possible to write much more readable Perl code (even within
144 regular expressions). Formerly cryptic variable names can be replaced
145 by mnemonic identifiers. Error messages are more informative, and the
146 optional warnings will catch many of the mistakes a novice might make.
147 This cannot be stressed enough. Whenever you get mysterious behavior,
148 try the B<-w> switch!!! Whenever you don't get mysterious behavior,
149 try using B<-w> anyway.
151 =item * Simplified grammar
153 The new yacc grammar is one half the size of the old one. Many of the
154 arbitrary grammar rules have been regularized. The number of reserved
155 words has been cut by 2/3. Despite this, nearly all old Perl scripts
156 will continue to work unchanged.
158 =item * Lexical scoping
160 Perl variables may now be declared within a lexical scope, like "auto"
161 variables in C. Not only is this more efficient, but it contributes
162 to better privacy for "programming in the large". Anonymous
163 subroutines exhibit deep binding of lexical variables (closures).
165 =item * Arbitrarily nested data structures
167 Any scalar value, including any array element, may now contain a
168 reference to any other variable or subroutine. You can easily create
169 anonymous variables and subroutines. Perl manages your reference
172 =item * Modularity and reusability
174 The Perl library is now defined in terms of modules which can be easily
175 shared among various packages. A package may choose to import all or a
176 portion of a module's published interface. Pragmas (that is, compiler
177 directives) are defined and used by the same mechanism.
179 =item * Object-oriented programming
181 A package can function as a class. Dynamic multiple inheritance and
182 virtual methods are supported in a straightforward manner and with very
183 little new syntax. Filehandles may now be treated as objects.
185 =item * Embeddable and Extensible
187 Perl may now be embedded easily in your C or C++ application, and can
188 either call or be called by your routines through a documented
189 interface. The XS preprocessor is provided to make it easy to glue
190 your C or C++ routines into Perl. Dynamic loading of modules is
191 supported, and Perl itself can be made into a dynamic library.
193 =item * POSIX compliant
195 A major new module is the POSIX module, which provides access to all
196 available POSIX routines and definitions, via object classes where
199 =item * Package constructors and destructors
201 The new BEGIN and END blocks provide means to capture control as
202 a package is being compiled, and after the program exits. As a
203 degenerate case they work just like awk's BEGIN and END when you
204 use the B<-p> or B<-n> switches.
206 =item * Multiple simultaneous DBM implementations
208 A Perl program may now access DBM, NDBM, SDBM, GDBM, and Berkeley DB
209 files from the same script simultaneously. In fact, the old dbmopen
210 interface has been generalized to allow any variable to be tied
211 to an object class which defines its access methods.
213 =item * Subroutine definitions may now be autoloaded
215 In fact, the AUTOLOAD mechanism also allows you to define any arbitrary
216 semantics for undefined subroutine calls. It's not for just autoloading.
218 =item * Regular expression enhancements
220 You can now specify nongreedy quantifiers. You can now do grouping
221 without creating a backreference. You can now write regular expressions
222 with embedded whitespace and comments for readability. A consistent
223 extensibility mechanism has been added that is upwardly compatible with
224 all old regular expressions.
226 =item * Innumerable Unbundled Modules
228 The Comprehensive Perl Archive Network described in L<perlmodlib>
229 contains hundreds of plug-and-play modules full of reusable code.
230 See F<http://www.perl.com/CPAN> for a site near you.
232 =item * Compilability
234 While not yet in full production mode, a working perl-to-C compiler
235 does exist. It can generate portable byte code, simple C, or
240 Okay, that's I<definitely> enough hype.
248 Larry Wall <F<larry@wall.org>>, with the help of oodles of other folks.
250 If your Perl success stories and testimonials may be of help to others
251 who wish to advocate the use of Perl in their applications,
252 or if you wish to simply express your gratitude to Larry and the
253 Perl developers, please write to <F<perl-thanks@perl.org>>.
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.