I don't think it's ever possible for $first to be undefined

You're right of course++

My only excuse is that it is an artifact of the iterative development process I went through as I tried to handle each different case. I think the test made sense at some point; but then again, maybe not :)

During the refactoring, I just attempted to remove some levels of nesting by moving things around, without breaking anything. I didn't actually consider why each condition was there at that point. It just highlights the value of peer review :)