∀ {α : Type u_1} {l : List α} (tail : List (List α)) (motive : (l' : List α) → l ∈ l' :: tail → Prop) (l' : List α)
  (h : l ∈ l' :: tail),
  (∀ (a : Unit), motive l ⋯) → (∀ (l' : List α) (hlMemL : List.Mem l tail), motive l' ⋯) → motive l' h