Goal:
  
  z : t
  hd : A.t
  tl : list A.t
  hd' : A.t
  tl' : list A.t
  H : A.lt hd hd'
  H'1' : list A.t
  H'1 : list A.t
  H' : lt_ H'1' H'1
  ============================
   ({| pr1 := hd' :: tl'; pr2 := z |} = {| pr1 := H'1'; pr2 := H'1 |} ->
    let H := CoreTactics.block in
    let H0 := CoreTactics.block in lt (hd :: tl) z)


DEBUG:Going to execute:
fun tac p =>
             let ty := type of p in
             let eliminator := eval simpl in DepElim.elim in
             tac p eliminator