interface Aircraft {
	method set_pitch (...);
}

class Jet : isa Aircraft {
	method set_pitch (...) {...}
}

##</code><code>##

class Jet {
	method set_pitch (...) {...}
}

interface FlyingThings {
	require method set_pitch (...);
}

##</code><code>##

class Piano {
	method set_pitch (...) {...}
}

##</code><code>##

	ThickInterface	ThinInterface
			\		/
			ThickThin

##</code><code>##

unshift @ThickInterface::ISA, 'ThinInterface';