simple Perl object base class

 Rose::Class is a generic base class for classes. It provides a single class
 method (error), but may be expanded further in the future.
 .
 A class that inherits from Rose::Class is not expected to allow objects
 of that class to be instantiated, since the namespace for class and object
 methods is shared. For example, it is common for Rose::Object-derived classes
 to have error methods, but this would conflict with the Rose::Class method of
 the same name.