I wonder if an eval("use Module"); would be more "correct" in cases where you may not wish to use a module until some optional point during your script's run...

I think your method of requireing/importing infrequently used modules is perfectly sane, but we are of course making the assumption that this behavior adequately performs the same task as use at compile-time. So long as that's not violated in future versions of Perl, I see no problem...