It's a long a rather complicated example. The main problem (not the only problem) is that I am implementing a REST interface and the path info is effectively a set of key/value pairs but ordering is important. Further, I need to sometimes insert default information before and after certain keys. I just need a simple interface which accomplishes this and tied hashes fail for a variety of reasons (not the least of which is the fact that I do not used tied variables unless I have no choice).