∀ {b e : String.Pos.Raw} (x : Substring.Raw) (mm : List Char)
  (motive : (∃ l' r', Substring.Raw.ValidFor l' mm r' (x.extract b e)) → Prop)
  (x_1 : ∃ l' r', Substring.Raw.ValidFor l' mm r' (x.extract b e)),
  (∀ (l' r' : List Char) (h₃ : Substring.Raw.ValidFor l' mm r' (x.extract b e)), motive ⋯) → motive x_1