Class::C3 is currently an experimental pragma to change Perl 5's standard method resolution order from depth-first left-to-right (a.k.a - pre-order) to the more sophisticated C3 method resolution order. . C3 is the name of an algorithm which aims to provide a sane method resolution order under multiple inheritence. It was first introduced in the langauge Dylan, and then later adopted as the preferred MRO (Method Resolution Order) for the new-style classes in Python 2.3. Most recently it has been adopted as the 'canonical' MRO for Perl 6 classes, and the default MRO for Parrot objects as well.