Goal:
    A : Type  P : A → A → Type  hd : A  hd' : A  tl : list A  p : P hd hd'
  ============================
   (hd' :: tl = [] ++ hd' :: tl)


DEBUG:Going to execute:
<Coq.Init.Tauto.is_unit_or_eq> flags X1; Ltac.cut X2