So I had to see PG's solution in arc1. Pretty nice as it removes some duplication and has a simpler (and more efficient) way to determine if a sub aif is needed:
(mac aif (expr . body)
`(let it ,expr
(if it
,@(if (cddr body)
`(,(car body) (aif ,@(cdr body)))
body))))
Duplication is removed by simple branching inside the `(let it ,expr ... part. And (cddr body) is shorter and more efficient than (<= (len body) 2).
