The answer is correct.

Well, yes, in fact it is. But some more info would have been benefical.

Without the "LIB=X", the .pm files are installed a couple of dir levels below the PREFIX, which means that you can't just add the "PREFIX" dir to your @INC. (I didn't test that "use lib '/u/mydir/perl';", so I assume what you are saying is that it works?)

I assume that is a good way of doing it, but it's not what I wanted for my own written modules.