The "mro" namespace provides several utilities for dealing with method resolution order and method caching in general in Perl 5.9.5 and higher. This module provides those interfaces for earlier versions of Perl (back to 5.6.0 anyways). It is a harmless no-op to use this module on 5.9.5+. That is to say, code which properly uses MRO::Compat will work unmodified on both older Perls and 5.9.5+. If you're writing a piece of software that would like to use the parts of 5.9.5+'s mro:: interfaces that are supported here, and you want compatibility with older Perls, this is the module for you. Some parts of this code will work better and/or faster with Class::C3::XS installed (which is an optional prereq of Class::C3, which is in turn a prereq of this package), but it's not a requirement. This module never exports any functions. All calls must be fully qualified with the mro:: prefix.