... pass a hash as an argument to a module.

Technically, what you are trying to do is pass a hash reference as an argument to a subroutine defined in a given package. (More precisely, since we're in OO-land now, to a method of a class.) It's possible to pass a hash or any other reference to a module when use-ing or require-ing it (see, e.g., constant), but that's another tale for another day. :)