It is real easy
on the command line
perl -v
should return something like this
This is perl, v5.6.1 built for i386-linux
Copyright 1987-2001, Larry Wall
Perl may be copied only under the terms of either the Artistic License or the
GNU General Public License, which may be found in the Perl 5 source kit.
Complete documentation for Perl, including FAQ lists, should be found on
this system using `man perl' or `perldoc perl'. If you have access to the
Internet, point your browser at
http://www.perl.com/, the Perl Home Page.