BEGIN is the sort of thing you write when you have code-generation tasks or want to otherwise have done work appropriate to a compile-time categorization. I wouldn't ordinarilly include things like setting $VERSION in that though there is some sense in including Exporter specific information at compile-time (even though it isn't code generation) - other things that have to run at compile-time are allowed to care about that information so it is potentially relavent at that time.