"It is usually a good idea to put "global variables" into a Common module of some kind, perhaps which exposes an object that simply serves as the repository of those values."

Do you mean explicit package + object oriented?

I already use a separate perl module and I'm thinking using explicit package name in addition. But I don't want to put object oriented programming with the rest of the code, which is not.

But I fully agree with you that explicit package name is a better practice (even for small projects like mine, it doesn't hurt).

And yes I already put use strict and use warnings everywhere :D