Goal:
  
  A : Type
  H : ReflectEq A
  l2 : list A
  l1 : list A
  l0 : list A
  l : list A
  ============================
   ({| pr1 := []; pr2 := l2 |} = {| pr1 := l1; pr2 := l0 |}
    → ([], [], l2) = split_prefix l1 l0
      → let H := CoreTactics.block in
        is_prefix l l1
        → is_prefix l l0 → is_prefix l (fst (fst (split_prefix l1 l0))))


DEBUG:Going to execute:
simplify * || simplify ?