Aside from trying
perldoc <module name>
individually for any CPAN module that takes my fancy or going through the file system and looking at the directories, I have no idea what modules we have installed.
What's the easiest way to just get a big list of every CPAN module installed? From the command line or otherwise.
This is answered in the Perl FAQ, the answer which can be quickly found with perldoc -q installed. In short, it comes down to using ExtUtils::Installed or using File::Find, variants of both of which have been covered previously in this thread.
You can also find the FAQ entry "How do I find which modules are installed on my system?" in perlfaq3. You can see a list of all FAQ answers by looking in perlfaq