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 perlvar Perl predefined variables
35 perlsub Perl subroutines
36 perlmod Perl modules: how they work
37 perlmodlib Perl modules: how to write and use
38 perlmodinstall Perl modules: how to install from CPAN
40 perllocale Perl locale support
42 perlref Perl references
43 perlreftut Perl references short introduction
44 perldsc Perl data structures intro
45 perllol Perl data structures: lists of lists
46 perltoot Perl OO tutorial
48 perltie Perl objects hidden behind simple variables
49 perlbot Perl OO tricks and examples
50 perlipc Perl interprocess communication
52 perldebug Perl debugging
53 perldiag Perl diagnostic messages
55 perltrap Perl traps for the unwary
56 perlport Perl portability guide
57 perlstyle Perl style guide
59 perlpod Perl plain old documentation
60 perlbook Perl book information
62 perlembed Perl ways to embed perl in your C or C++ application
63 perlapio Perl internal IO abstraction interface
64 perlxs Perl XS application programming interface
65 perlxstut Perl XS tutorial
66 perlguts Perl internal functions for those doing extensions
67 perlcall Perl calling conventions from C
69 perlhist Perl history records
71 (If you're intending to read these straight through for the first time,
72 the suggested order will tend to reduce the number of forward references.)
74 By default, all of the above manpages are installed in the
75 F</usr/local/man/> directory.
77 Extensive additional documentation for Perl modules is available. The
78 default configuration for perl will place this additional documentation
79 in the F</usr/local/lib/perl5/man> directory (or else in the F<man>
80 subdirectory of the Perl library directory). Some of this additional
81 documentation is distributed standard with Perl, but you'll also find
82 documentation for third-party modules there.
84 You should be able to view Perl's documentation with your man(1)
85 program by including the proper directories in the appropriate start-up
86 files, or in the MANPATH environment variable. To find out where the
87 configuration has installed the manpages, type:
91 If the directories have a common stem, such as F</usr/local/man/man1>
92 and F</usr/local/man/man3>, you need only to add that stem
93 (F</usr/local/man>) to your man(1) configuration files or your MANPATH
94 environment variable. If they do not share a stem, you'll have to add
97 If that doesn't work for some reason, you can still use the
98 supplied F<perldoc> script to view module information. You might
99 also look into getting a replacement man program.
101 If something strange has gone wrong with your program and you're not
102 sure where you should look for help, try the B<-w> switch first. It
103 will often point out exactly where the trouble is.
107 Perl is a language optimized for scanning arbitrary
108 text files, extracting information from those text files, and printing
109 reports based on that information. It's also a good language for many
110 system management tasks. The language is intended to be practical
111 (easy to use, efficient, complete) rather than beautiful (tiny,
114 Perl combines (in the author's opinion, anyway) some of the best
115 features of C, B<sed>, B<awk>, and B<sh>, so people familiar with
116 those languages should have little difficulty with it. (Language
117 historians will also note some vestiges of B<csh>, Pascal, and even
118 BASIC-PLUS.) Expression syntax corresponds quite closely to C
119 expression syntax. Unlike most Unix utilities, Perl does not
120 arbitrarily limit the size of your data--if you've got the memory,
121 Perl can slurp in your whole file as a single string. Recursion is of
122 unlimited depth. And the tables used by hashes (sometimes called
123 "associative arrays") grow as necessary to prevent degraded
124 performance. Perl can use sophisticated pattern matching techniques to
125 scan large amounts of data very quickly. Although optimized for
126 scanning text, Perl can also deal with binary data, and can make dbm
127 files look like hashes. Setuid Perl scripts are safer than C programs
128 through a dataflow tracing mechanism which prevents many stupid
131 If you have a problem that would ordinarily use B<sed> or B<awk> or
132 B<sh>, but it exceeds their capabilities or must run a little faster,
133 and you don't want to write the silly thing in C, then Perl may be for
134 you. There are also translators to turn your B<sed> and B<awk>
135 scripts into Perl scripts.
137 But wait, there's more...
139 Perl version 5 is nearly a complete rewrite, and provides
140 the following additional benefits:
144 =item * Many usability enhancements
146 It is now possible to write much more readable Perl code (even within
147 regular expressions). Formerly cryptic variable names can be replaced
148 by mnemonic identifiers. Error messages are more informative, and the
149 optional warnings will catch many of the mistakes a novice might make.
150 This cannot be stressed enough. Whenever you get mysterious behavior,
151 try the B<-w> switch!!! Whenever you don't get mysterious behavior,
152 try using B<-w> anyway.
154 =item * Simplified grammar
156 The new yacc grammar is one half the size of the old one. Many of the
157 arbitrary grammar rules have been regularized. The number of reserved
158 words has been cut by 2/3. Despite this, nearly all old Perl scripts
159 will continue to work unchanged.
161 =item * Lexical scoping
163 Perl variables may now be declared within a lexical scope, like "auto"
164 variables in C. Not only is this more efficient, but it contributes
165 to better privacy for "programming in the large". Anonymous
166 subroutines exhibit deep binding of lexical variables (closures).
168 =item * Arbitrarily nested data structures
170 Any scalar value, including any array element, may now contain a
171 reference to any other variable or subroutine. You can easily create
172 anonymous variables and subroutines. Perl manages your reference
175 =item * Modularity and reusability
177 The Perl library is now defined in terms of modules which can be easily
178 shared among various packages. A package may choose to import all or a
179 portion of a module's published interface. Pragmas (that is, compiler
180 directives) are defined and used by the same mechanism.
182 =item * Object-oriented programming
184 A package can function as a class. Dynamic multiple inheritance and
185 virtual methods are supported in a straightforward manner and with very
186 little new syntax. Filehandles may now be treated as objects.
188 =item * Embeddable and Extensible
190 Perl may now be embedded easily in your C or C++ application, and can
191 either call or be called by your routines through a documented
192 interface. The XS preprocessor is provided to make it easy to glue
193 your C or C++ routines into Perl. Dynamic loading of modules is
194 supported, and Perl itself can be made into a dynamic library.
196 =item * POSIX compliant
198 A major new module is the POSIX module, which provides access to all
199 available POSIX routines and definitions, via object classes where
202 =item * Package constructors and destructors
204 The new BEGIN and END blocks provide means to capture control as
205 a package is being compiled, and after the program exits. As a
206 degenerate case they work just like awk's BEGIN and END when you
207 use the B<-p> or B<-n> switches.
209 =item * Multiple simultaneous DBM implementations
211 A Perl program may now access DBM, NDBM, SDBM, GDBM, and Berkeley DB
212 files from the same script simultaneously. In fact, the old dbmopen
213 interface has been generalized to allow any variable to be tied
214 to an object class which defines its access methods.
216 =item * Subroutine definitions may now be autoloaded
218 In fact, the AUTOLOAD mechanism also allows you to define any arbitrary
219 semantics for undefined subroutine calls. It's not for just autoloading.
221 =item * Regular expression enhancements
223 You can now specify nongreedy quantifiers. You can now do grouping
224 without creating a backreference. You can now write regular expressions
225 with embedded whitespace and comments for readability. A consistent
226 extensibility mechanism has been added that is upwardly compatible with
227 all old regular expressions.
229 =item * Innumerable Unbundled Modules
231 The Comprehensive Perl Archive Network described in L<perlmodlib>
232 contains hundreds of plug-and-play modules full of reusable code.
233 See F<http://www.perl.com/CPAN> for a site near you.
235 =item * Compilability
237 While not yet in full production mode, a working perl-to-C compiler
238 does exist. It can generate portable byte code, simple C, or
243 Okay, that's I<definitely> enough hype.
251 Larry Wall <F<larry@wall.org>>, with the help of oodles of other folks.
253 If your Perl success stories and testimonials may be of help to others
254 who wish to advocate the use of Perl in their applications,
255 or if you wish to simply express your gratitude to Larry and the
256 Perl developers, please write to <F<perl-thanks@perl.org>>.
260 "@INC" locations of perl libraries
264 a2p awk to perl translator
266 s2p sed to perl translator
270 The B<-w> switch produces some lovely diagnostics.
272 See L<perldiag> for explanations of all Perl's diagnostics. The C<use
273 diagnostics> pragma automatically turns Perl's normally terse warnings
274 and errors into these longer forms.
276 Compilation errors will tell you the line number of the error, with an
277 indication of the next token or token type that was to be examined.
278 (In the case of a script passed to Perl via B<-e> switches, each
279 B<-e> is counted as one line.)
281 Setuid scripts have additional constraints that can produce error
282 messages such as "Insecure dependency". See L<perlsec>.
284 Did we mention that you should definitely consider using the B<-w>
289 The B<-w> switch is not mandatory.
291 Perl is at the mercy of your machine's definitions of various
292 operations such as type casting, atof(), and floating-point
293 output with sprintf().
295 If your stdio requires a seek or eof between reads and writes on a
296 particular stream, so does Perl. (This doesn't apply to sysread()
299 While none of the built-in data types have any arbitrary size limits
300 (apart from memory size), there are still a few arbitrary limits: a
301 given variable name may not be longer than 251 characters. Line numbers
302 displayed by diagnostics are internally stored as short integers,
303 so they are limited to a maximum of 65535 (higher numbers usually being
304 affected by wraparound).
306 You may mail your bug reports (be sure to include full configuration
307 information as output by the myconfig program in the perl source tree,
308 or by C<perl -V>) to <F<perlbug@perl.com>>.
309 If you've succeeded in compiling perl, the perlbug script in the utils/
310 subdirectory can be used to help mail in a bug report.
312 Perl actually stands for Pathologically Eclectic Rubbish Lister, but
313 don't tell anyone I said that.
317 The Perl motto is "There's more than one way to do it." Divining
318 how many more is left as an exercise to the reader.
320 The three principal virtues of a programmer are Laziness,
321 Impatience, and Hubris. See the Camel Book for why.