The documentation is correct, of course!

In my first implementation, the class attributes are declared as :ATTR, and they behave as described. That's why that implementation does not have its own DEMOLISH (called by the Class::Std DESTROY). That is, in a way, its advantage. You do your work up front in a way that the module takes care of the rest of the work at the end.

The difference between what I have declared as :ATTR and what is normally declared as :ATTR is that normally the elements of the hash are all different. Each instance has its own key and value. In my case, the values of an individual hash are all the same—one reference shared by every instance. (Each still has its own key, but they all have the same value.) I'm tricking the instance attributes into behaving as class attributes.

In the second implementation, the class attributes are not declared as :ATTR at all, so I have to clean them up myself with my own DEMOLISH.