Goal:
    z : t  hd : A.t  tl : list A.t  H : lt (hd :: tl) z
  ============================
   (lt [] z)


DEBUG:Going to execute:
(DepElim.is_introduced H; CoreTactics.block_goal;
             CoreTactics.revert_until H; CoreTactics.block_goal) ||
             (let H' := fresh H in
              intros until H'; CoreTactics.block_goal) ||
               (intros; CoreTactics.block_goal)