perl-Class-ISA

Suppose you have a class (like Food::Fish::Fishstick) that is derived,
via its @ISA, from one or more superclasses (as Food::Fish::Fishstick
is from Food::Fish, Life::Fungus, and Chemicals), and some of those
superclasses may themselves each be derived, via its @ISA, from one
or more superclasses (as above).

When, then, you call a method in that class ($fishstick->calories),
Perl first searches there for that method, but if it's not there, it
goes searching in its superclasses, and so on, in a depth-first (or
maybe "height-first" is the word) search. In the above example, it'd
first look in Food::Fish, then Food, then Matter, then Life::Fungus,
then Life, then Chemicals.

This library, Class::ISA, provides functions that return that list
-- the list (in order) of names of classes Perl would search to find
a method, with no duplicates.