My latest approach is to reduce this to just three methods, a define method that recursively sets anything anywhere in a multilevel hash or hash of arrays or any combination to which there is a blessed reference to the top; a recursive get method that is insensitive to reference types and similarly a prune method that deletes anywhere in the tree. But I am still checking whether the prune method needs to collect its own garbage or whether 'delete' is recursive before I would publish examples.