And I've wondered if I must export functions, strings, arrays, etc. etc. that are not used outside of the PM module?

I just want to point out that (as you may already know) functions, package variables and package constants can all be accessed from the "outside" even if they're not exported. They just have to be accessed via their fully qualified names - eg My::Mod::foo() instead of simply foo(), $My::Mod::package_var instead of $package_var and My::Mod::CONST_VAL instead of CONST_VAL.

Cheers,
Rob