The '''oo::configurable''' class is a part of [TclOO] in Tcl 8.7. It is a metaclass, i.e., it modifies how you create classes, adding the capability to define ''properties'' on the class. It also modifies the class to add a '''configure''' method (via a mixin). The '''configure''' method is aware of the properties defined across the inheritance hierarchy for the class. <> TclOO