Goal:
    T : Type -> Type  M : Monad T
  ============================
   (forall (A : Type) (P Q : A -> Type),
    (forall x : A, ∥ Q x ∥ -> T (∥ P x ∥)) ->
    list A ->
    forall (a : A) (l : list A), ∥ All Q (a :: l) ∥ -> ∥ P a ∥ -> ∥ All Q l ∥)


DEBUG:Going to execute:
<coq-core.plugins.ltac::intro@1> $1