Class::Modular is a superclass for generating modular classes, where methods can be added into the class from the perspective of the object, rather than from the perspective of the class.
See perldoc Class::Modular for more information, and COPYING for copyright and licensing information.
Current development versions are available at http://rzlab.ucr.edu/cgi-bin/viewcvs.cgi/trunk/?root=Class+Modular
Da::DB makes extensive use of Class::Modular, and is available at http://rzlab.ucr.edu/cgi-bin/viewcvs.cgi/?root=Da+DB and should be comming soon to a CPAN mirror near you.