Arguments perm[A].
Section Uniq.
Variable A: Type.
Inductive uniq: list A -> Prop :=
uniq_nil: uniq nil
| uniq_cons: forall a l, ~ In a l -> uniq l -> uniq (a::l).

Lemma uniq_perm l1 l2: perm l1 l2 -> uniq l1 -> uniq l2.