Stack pattern match

Imagine you have a reference implementation of a btree and a reference implementation of a locking manager and a security manager and you want to tie them together. You could add code calls from one to the other but what if there is a better way? The better way for extensibility is to match stack function calldepths to code snippets that run whenever the pattern is matched. For example when a btree is split you might want to acquire locks or release locks in a certain order. We can do pattern matching around the callsite of a btree split and return values and do the right locking and security behaviours without needing to change the API of either. Essentially you have parallel multiple return values.