Compare 'Lambda: the ultimate GOTO' https://www2.cs.sfu.ca/CourseCentral/383/havens/pubs/lambda-... which also uses state machines as its motivating example.

With TCO, a state transition is implemented just as a function call. I find it very elegant and see TCO as great bonus in programming languages.

I haven't thought about this in years! Julian Noble was one of my teachers back when I was an undergrad.