Add Mixin::Event::Dispatch in as a parent to your class, and it'll provide some
methods for defining event handlers ("subscribe_to_event" or
"add_handler_for_event") and calling them ("invoke_event").

Note that handlers should return 0 for a one-off handler, and 1 if it should be
called again on the next event.

WWW: http://search.cpan.org/dist/Mixin-Event-Dispatch/