Your point is well taken. What I mean to say is that (especially in a shared-hosting situation) it is often convenient to execute a very-short program whose sole purpose is to execute a use lib statement (to push paths onto @INC), then call the original main-program. The other way to do it is to somehow ensure a correct value for PERL5LIB but I tend to like this way better.
It has also been a real bone of contention for me that lots of hosting-services pay a great deal attention to PHP but run truly-antique versions of Perl ... and also place sometimes-too-severe resource limit restrictions. You have to shop carefully.