Current Perl documentation can be found at perldoc.perl.org.
Here is our local, out-dated (pre-5.6) version:
CPAN stands for Comprehensive Perl Archive Network, a huge archive replicated on dozens of machines all over the world. CPAN contains source code, non-native ports, documentation, scripts, and many third-party modules and extensions, designed for everything from commercial database interfaces to keyboard/screen control to web walking and CGI scripts. The master machine for CPAN is ftp://ftp.funet.fi/pub/languages/perl/CPAN/, but you can use the address http://www.perl.com/CPAN/CPAN.html to fetch a copy from a ``site near you''. See http://www.perl.com/CPAN (without a slash at the end) for how this process works.
CPAN/path/... is a naming convention for files available on CPAN sites. CPAN indicates the base directory of a CPAN mirror, and the rest of the path is the path from that directory to the file. For instance, if you're using ftp://ftp.funet.fi/pub/languages/perl/CPAN as your CPAN site, the file CPAN/misc/japh file is downloadable as ftp://ftp.funet.fi/pub/languages/perl/CPAN/misc/japh .
Considering that there are hundreds of existing modules in the archive, one probably exists to do nearly anything you can think of. Current categories under CPAN/modules/by-category/ include perl core modules; development support; operating system interfaces; networking, devices, and interprocess communication; data type utilities; database interfaces; user interfaces; interfaces to other languages; filenames, file systems, and file locking; internationalization and locale; world wide web support; server and daemon utilities; archiving and compression; image manipulation; mail and news; control flow utilities; filehandle and I/O; Microsoft Windows modules; and miscellaneous modules.