fall-through, or <code class="mendoza-code">case</code> in some
Lisps, though simpler.  <code class="mendoza-code">when</code> is like <code class="mendoza-code">if</code>, but returns <code class="mendoza-code">nil</code> if
the condition evaluates to <code class="mendoza-code">nil</code> or <code class="mendoza-code">false</code>, similar to the macro of
the same name in Common Lisp and Clojure. For looping, <code class="mendoza-code">loop</code>, <code class="mendoza-code">seq</code>,
and <code class="me