"catastrophe" is certainly over-stated. Since the extra disk interactions to load the module will still be fairly small and will only be done once over the hopefully thousands of requests that will be handled by one apached process, the impact of having to load a module in every apached child is likely not very significant.

As for sharing memory, that can work to the extent that the things loaded into memory by the module land on pages that are never modified in the child processes. Given the nature of Perl, I suspect that only a minority of the extra memory allocated will stay shared for a significant length of time, perhaps only a tiny fraction of it.

So the down-side to delayed loading under mod_perl is often going to be quite minor, I expect.

So I'd lean toward delayed loading and use mod_perl start-up options to force pre-loading of widely-used larger pieces.