#[global]
Instance CPermutation_Forall A (P : A -> Prop) :
  Proper (@CPermutation A ==> Basics.impl) (Forall P).#[global]
Instance CPermutation_Exists A (P : A -> Prop) :
  Proper (@CPermutation A ==> Basics.impl) (Exists P).

(* Specifications: *)
Lemma CPermutation_Forall2 A B (P : A -> B -> Prop) : forall l1 l1' l2, CPermutation l1 l1' -> Forall2 P l1 l2 -> exists l2', CPermutation l2 l2' /\ Forall2 P l1' l2'.