Global Instance Permutation_NoDup' :
 Proper (@Permutation A ==> iff) (@NoDup A).

Lemma Permutation_incl_cons_inv_r (l1 l2 : list A) a : incl l1 (a :: l2) -> exists n l3, Permutation l1 (repeat a n ++ l3) /\ incl l3 l2.