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