don't use the `case` form, use `cond` instead
The `case` form is terrible, and I wish it didn't exist. I never use it, and I've only seen new Racketeers use it wrong. You never want `case`, you want `cond` or `match` instead. The `case` form only allows literal data in the match, so if you try to use a variable it will be interpreted as a symbol instead! Moreover, `case` and `cond` both have a terrible design mistake that the fall-through case returns `void` instead of raising an error! I've only seen `case` result in tiresome debugging.