Thank you and PodMaster, I followed your advices. Moreover, I rethought the design and put restriction for myself: to preload all Foo::Basic::* modules with use Foo. I't all kind of plugins (Foo::Plugin::*), with overloading basic system functionality (Foo::Basic::*), so this way I always know what Foo::Plugin::* modules to search (for each Foo::Basic::*) to try to require them.