perl [ __-sTuU__? [ __-hv__? ''configvar''? ] [ __-cw__? ''debugger''? ] __-D__[[''number/list''? ] [ __-pna__? __-F__''pattern''? [ __-l__[[''octal''? ] __-0__[[''octal''? ] [ __-I__''dir''? __-m__[[__-__?module ] __-M__[[__-__?'module...' ] [ __-P__? __-S__? [ __-x__[[''dir''? ] __-i__[[''extension''? ] [ __-e__ '''command'''? [ __--__? [ ''programfile''? [ ''argument''?...
perlamiga Perl notes for Amiga perlbs2000 Perl notes for POSIX-BC BS2000 perlcygwin Perl notes for Cygwin perldos Perl notes for DOS perlepoc Perl notes for EPOC perlhpux Perl notes for HP-UX perlmachten Perl notes for Power !MachTen? perlmacos Perl notes for Mac OS (Classic) perlmpeix Perl notes for MPE/iX perlos2 Perl notes for OS/2 perlos390 Perl notes for OS/390 perlsolaris Perl notes for Solaris perlvmesa Perl notes for VM/ESA perlvms Perl notes for VMS perlvos Perl notes for Stratus VOS perlwin32 Perl notes for Windows (If you're intending to read these straight through for the first time, the suggested order will tend to reduce the number of forward references.)
On Debian systems, you need to install the perl-doc package which contains the majority of the standard Perl documentation and the perldoc program.
Extensive additional documentation for Perl modules is available, both those distributed with Perl and third-party modules which are packaged or locally installed.
Perl is a language optimized for scanning arbitrary text files, extracting information from those text files, and printing reports based on that information. It's also a good language for many system management tasks. The language is intended to be practical (easy to use, efficient, complete) rather than beautiful (tiny, elegant, minimal).
Perl combines (in the author's opinion, anyway) some of the best features of C, sed, awk, and sh, so people familiar with those languages should have little difficulty with it. (Language historians will also note some vestiges of csh, Pascal, and even BASIC-PLUS .) Expression syntax corresponds closely to C expression syntax. Unlike most Unix utilities, Perl does not arbitrarily limit the size of your data--if you've got the memory, Perl can slurp in your whole file as a single string. Recursion is of unlimited depth. And the tables used by hashes (sometimes called ``associative arrays'') grow as necessary to prevent degraded performance. Perl can use sophisticated pattern matching techniques to scan large amounts of data quickly. Although optimized for scanning text, Perl can also deal with binary data, and can make dbm files look like hashes. Setuid Perl scripts are safer than C programs through a dataflow tracing mechanism that prevents many stupid security holes.
If you have a problem that would ordinarily use sed or awk or sh, but it exceeds their capabilities or must run a little faster, and you don't want to write the silly thing in C, then Perl may be for you. There are also translators to turn your sed and awk scripts into Perl scripts.
But wait, there's more...
Begun in 1993 (see perlhist), Perl version 5 is nearly a complete rewrite that provides the following additional benefits:
modularity and reusability using innumerable modules
Described in perlmod, perlmodlib, and perlmodinstall.
embeddable and extensible
Described in perlembed, perlxstut, perlxs, perlcall, perlguts, and xsubpp.
roll-your-own magic variables (including multiple simultaneous DBM implementations)
Described in perltie and AnyDBM_File.
subroutines can now be overridden, autoloaded, and prototyped
Described in perlsub.
arbitrarily nested data structures and anonymous functions
Described in perlreftut, perlref, perldsc, and perllol.
Described in perlobj, perltoot, and perlbot.
compilability into C code or Perl bytecode
Described in B and B::Bytecode.
support for light-weight processes (threads)
Described in perlthrtut and Thread.
support for internationalization, localization, and Unicode
Described in perllocale and utf8.
Described in perlsub.
regular expression enhancements
Described in perlre, with additional examples in perlop.
enhanced debugger and interactive Perl environment, with integrated editor support
Described in perldebug.
POSIX 1003.1 compliant library
Described in POSIX .
The use warnings pragma (and the -w switch) produces some lovely diagnostics.
See perldiag for explanations of all Perl's diagnostics. The use diagnostics pragma automatically turns Perl's normally terse warnings and errors into these longer forms.
Compilation errors will tell you the line number of the error, with an indication of the next token or token type that was to be examined. (In a script passed to Perl via -e switches, each -e is counted as one line.)
Setuid scripts have additional constraints that can produce error messages such as ``Insecure dependency''. See perlsec.
The -w switch is not mandatory.
Perl is at the mercy of your machine's definitions of various operations such as type casting, atof(), and floating-point output with sprintf().
If your stdio requires a seek or eof between reads and writes on a particular stream, so does Perl. (This doesn't apply to sysread() and syswrite().)
While none of the built-in data types have any arbitrary size limits (apart from memory size), there are still a few arbitrary limits: a given variable name may not be longer than 251 characters. Line numbers displayed by diagnostics are internally stored as short integers, so they are limited to a maximum of 65535 (higher numbers usually being affected by wraparound).
You may mail your bug reports (be sure to include full configuration information as output by the myconfig program in the perl source tree, or by perl -V) to firstname.lastname@example.org . If you've succeeded in compiling perl, the perlbug script in the utils/ subdirectory can be used to help mail in a bug report.
The Perl motto is ``There's more than one way to do it.'' Divining how many more is left as an exercise to the reader.