um, thanks. Does not answer the question.

I suppose this comes back to my confession that the question is really not perl related, but I was hoping someone else had faced+resolved this before.

UPDATE: Let me elaborate to satisfy those with trigger-happy downvote fingers: I've already done the diagnosing, and yes, the environment variable is not being set when users login. I was hoping someone had encountered this before on CentOS/Linux and knew how to correctly set an env variable which all users got when they logged in. The fact that it's PERL5LIB is actually incidental.