I'm trying to avoid a series of if/elsif's

I think you have made a poor choice of goals. This is not a situation where you have one input value that you want to test for a bunch of mutually exclusive possible values, where a dispatch table would be appropriate. You have several apparently unrelated conditions that you need to test in order. That calls for a chain of if/elsifs, and you're not saving anything by avoiding them (except perhaps some Confusing warning with if/elsif/else).