evaluating (as given in above solutions) is the correct solution at run time but if you want a list of installed modules for a quick reference in future, there is a perl script 'instmodsh' which is shipped with Perl. (At least I have it installed with perl-5.8.8-18.el5 :) ). In my system it is installed at path /usr/bin/instmodsh so I can run it directly as a shell command.