How can I tell if a perl module is installed?

TO LOOK FOR A SPECIFIC MODULE:
find `perl -e '{print join $/, grep {/[^.]/} @INC}'` -name '*pm' 2>/dev/null |grep -i <>

where <> is the name of the module you are looking for

TO LIST ALL INSTALLED MODULES:
find `perl -e '{print join $/, grep {/[^.]/} @INC}'` -name '*pm' 2>/dev/null