Support for creating serializable "inside-out" classes

 Class::Std introduced the "inside-out" model for classes (perldoc Class::Std
 for details). Among its salient features is complete encapsulation; that is,
 an object's data may only be accessed via its methods, unlike the usual
 hashref model that permits direct access by any code whatsoever. However, the
 drawback of complete encapsulation is that normal mechanisms for
 serialization won't work, as they rely on direct access to an object's
 attributes.
 .
 This class provides the class-building functionality from Class::Std, and in
 addition provides an interface to allow Storable to freeze and thaw any
 declared attributes of this class and any superclasses that were built via
 Class::Std::Storable.
 .
 However, in order to let Storable save attributes and construct the object,
 it is necessary to expose the attributes of the class to the world. Thus, any
 code could use the same interface that Storable does to get a copy of object
 attributes and create new objects with arbitrary attributes without going
 through the constructor. While the interface CAN'T be used to replace the
 existing attributes of an object, it COULD be used to create an arbitrarily
 mutated clone of an object without going through its methods. Also, if
 attributes are themselves references, then the objects to which they refer
 can be obtained and modified.