There is also the potential that this is an environment issue or permissions. There are variables that can change where stuff is looked for on the system (LD_LIBRARY_PATH, PERL5LIB, PATH, ...) that may be set differently on a user-by-user basis.

You could do an env from your own login and the login of the web server, and compare the differences. I would guess that the web server is a bit more restricted / limited / just plain different than your user's environment.