simple class variable accessors

 Class::Accessor::Class provides a simple way to create accessor and
 mutator methods for class variables, just as Class::Accessor provides
 for objects. It can use either an enclosed lexical variable, or a
 package variable.
 .
 This module was once implemented in terms of Class::Accessor, but
 changes to that module broke this relationship. Class::Accessor::Class
 is still a subclass of Class::Accessor, strictly for historical
 reasons. As a side benefit, a class that isa Class::Accessor::Class is
 also a Class::Accessor and can use its methods.