Current Perl documentation can be found at perldoc.perl.org.
Here is our local, out-dated (pre-5.6) version:
The complete Perl documentation is available with the perl distribution. If
you have perl installed locally, you probably have the documentation
installed as well: type
man perl if you're on a system resembling Unix. This will lead you to other important man pages, including how to set your
$MANPATH. If you're not on a Unix system, access to the documentation will be different; for example, it might be only in
HTML format. But all proper perl installations have fully-accessible documentation.
You might also try
perldoc perl in case your system doesn't have a proper man command, or it's been
misinstalled. If that doesn't work, try looking in /usr/local/lib/perl5/pod
If all else fails, consult the CPAN/doc directory, which contains the complete documentation in various formats, including native pod, troff, html, and plain text. There's also a web page at http://www.perl.com/perl/info/documentation.html that might help.
Many good books have been written about Perl -- see the section below for more details.