Goal:
  
  A : Type
  P : list A → list A → A → A → Type
  e : NoConfusion_All2_fold A P
        {| pr1 := {| pr1 := []; pr2 := [] |}; pr2 := All2_fold_nil P |}
        {| pr1 := {| pr1 := []; pr2 := [] |}; pr2 := All2_fold_nil P |}
  ============================
   (let H := CoreTactics.block in
    noConfusion_All2_fold_obligation_2 A P
      {| pr1 := {| pr1 := []; pr2 := [] |}; pr2 := All2_fold_nil P |}
      {| pr1 := {| pr1 := []; pr2 := [] |}; pr2 := All2_fold_nil P |}
      (noConfusion_All2_fold_obligation_1 A P
         {| pr1 := {| pr1 := []; pr2 := [] |}; pr2 := All2_fold_nil P |}
         {| pr1 := {| pr1 := []; pr2 := [] |}; pr2 := All2_fold_nil P |} e) =
    e)


DEBUG:Going to execute:
match goal with
           | |- let _ := CoreTactics.block in _ => intros _
           | |- _ => try (intro; CoreTactics.intros_until_block)
           end