Class::Data::Inheritable is for creating accessors/mutators to class
 data. That is, if you want to store something about your class as a
 whole (instead of about a single object). This data is then inherited
 by your subclasses and can be overridden.
 .
 For example:
 .
 Pere::Ubu->mk_classdata('Suitcase');
 .
 will generate the method Suitcase() in the class Pere::Ubu.
 .
 This new method can be used to get and set a piece of class data.
 .
 Pere::Ubu->Suitcase('Red');
 $suitcase = Pere::Ubu->Suitcase;