This is getting into details of semantics, but I'm not sure if your example is really shows that the language supports dynamic typing. It's more like an example

This is getting into details of semantics, but I'm not sure if your example is really shows that the language supports dynamic typing. It's more like an example of implementing dynamic typing in a static language. After all, you're not using the language's type system to do run-time type checking. You're using run-time pattern matching as a substitute. Of course, I'm just being pernickety, but that's how I am :)