Perhaps passing a perl -Idirectory perlfile in the ksh script? Or have you done that?

Also, you could try tweeking the .profile file for the user.

UPDATE: I like masem's better. Also, if you have access, try logging in directly as the user and see what happens.

HTH
--
idnopheq
Apply yourself to new problems without preparation, develop confidence in your ability to to meet situations as they arrise.

~ Shunryu Suzuki