To answer your specific question, the %INC hash keeps track of what has been loaded via do, require, or use --- if you want to re-require a file, simply delete its entry in the %INC hash and require it again (see the %INC entry in the perlvar manpage). However, you may want to rethink your design --- with more information on why you want to do this and what problem you are trying to solve, we might be able to offer better solutions.