But how does Perl find those non-standard libraries after you have installed? Or are these only things that are needed during testing?

The PERL5LIB environment variable and use lib both come to mind. I need a better understanding of your situation to see why you want to have these site-specific things written into the Makefile. Right now I'm think that is the wrong way to do it (it certainly seems difficult).

        - tye (but my friends call me "Tye")