Priority:
	- update documentation
	- for a start, improve coverage of tests (see below)
	- go beyond what Devel::Cover provides, e.g. variable number of arguments

Nice-to-have:
	- have an option to restrict new rules to their own name
	- same as above for main: only main can access ''
	- have an option to unshift into the existing rules (helpful for '')
	- tracing/logging feature to document who defined and who used what
	- find out how 'use MRO::Compat;' could automatically be added for older Perls

