Programming Perl, 4th Edition

mro

use mro;       # enables next::method and friends globally

use mro "dfs"; # enable DFS MRO for this class (Perl default)
use mro "c3";  # enable C3 MRO for this class

By default, Perl searches for methods with a depth-first search through the classes (package names) in @INC. The mro pragma changes that method resolution order. Specifying dfs uses the default depth-first search, while specifying c3 uses the C3 algorithm to resolve certain ambiguities in multiple inheritance. Without an import list, keeps the default method resolution order by enabling features that interact with C3 method resolution (see Chapter 12).