Yes, require happens at runtime - that's why I said fork first. Only the child loads the module to do the deed and then exits, so the parent process doesn't acquire any bloat.

(Not that I'm entirely convinced that loading modules per se costs a lot of space - more likely it is accumulated data structures that cause the Perl process to grow exorbitantly. That's mainly a matter of scoping stuff closely, and otherwise being attentive.)

Makeshifts last the longest.