In many cases you can type perl -M<module> (e.g, perl -MDigest::MD5) and perl will either pause waiting for input (if you have the module installed) or it will issue an error message (if you don't have it installed).
I use to do perl -M<module> -e exit in those cases, so that it won't pause. Or, when I have to test for many modules and using a Bourne-like shell in UNIX (e.g.: bash):
for MODULE in First::Module Second::Module Third::Module ; do perl -M$MODULE -e exit ; done
Ciao!
--bronto
In theory, there is no difference between theory and practice. In practice, there is.