As you enter your Perl script you have all the installed modules as .pm files below the folders in @INC so a small bash script will do the job for you:
#!/bin/bash
echo -e -n "Content-type: text/plain\n\n"
inc=`perl -e '$, = "\n"; print @INC;'`
for d in $inc
do
find $d -name '*.pm'
done