The execution is fine.

The constructor for Obj as chromatic wrote it will cheerfully construct things for subclasses.

However his very good point is that there appears to be no point in having your readers and writers have the methods in Obj, or vica versa. It is very easy to just say, "inherit", but inheritance used too often loses the point.

For serious food for thought, look through how LWP works. You will find a lot of classes, but things of different types (eg user agents, requests, responses) don't inherit from each other even though they interact quite a bit. And the design of the whole benefits from that.