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