2.13 Dispatch: case
Evaluates val-expr and uses the result to select a case-clause. The selected clause is the first one with a datum whose quoted form is eqv? to the result of val-expr. If no such datum is present, the else case-clause is selected; if no else case-clause is present, either, then the result of the case form is #<void>.
A case-clause that starts with else must be the last case-clause.