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