Goal:
  
  A : Type
  B : Type
  P : B → A → A → Type
  b0 : B
  bs : list B
  hd : A
  tl : list A
  tl' : list A
  a : OnOne2All P bs tl tl'
  b : B
  bs0 : list B
  hd0 : A
  hd' : A
  tl0 : list A
  p : P b hd0 hd'
  e : #|bs0| = #|tl0|
  ============================
   (∀ e0 : NoConfusion_OnOne2All A B P
             {|
               pr1 :=
                 {|
                   pr1 := b0 :: bs;
                   pr2 := {| pr1 := hd :: tl; pr2 := hd :: tl' |}
                 |};
               pr2 := OnOne2All_tl P b0 bs hd tl tl' a
             |}
             {|
               pr1 :=
                 {|
                   pr1 := b :: bs0;
                   pr2 := {| pr1 := hd0 :: tl0; pr2 := hd' :: tl0 |}
                 |};
               pr2 := OnOne2All_hd P b bs0 hd0 hd' tl0 p e
             |},
      let H := CoreTactics.block in
      noConfusion_OnOne2All_obligation_2 A B P
        {|
          pr1 :=
            {|
              pr1 := b0 :: bs; pr2 := {| pr1 := hd :: tl; pr2 := hd :: tl' |}
            |};
          pr2 := OnOne2All_tl P b0 bs hd tl tl' a
        |}
        {|
          pr1 :=
            {|
              pr1 := b :: bs0;
              pr2 := {| pr1 := hd0 :: tl0; pr2 := hd' :: tl0 |}
            |};
          pr2 := OnOne2All_hd P b bs0 hd0 hd' tl0 p e
        |}
        (noConfusion_OnOne2All_obligation_1 A B P
           {|
             pr1 :=
               {|
                 pr1 := b0 :: bs;
                 pr2 := {| pr1 := hd :: tl; pr2 := hd :: tl' |}
               |};
             pr2 := OnOne2All_tl P b0 bs hd tl tl' a
           |}
           {|
             pr1 :=
               {|
                 pr1 := b :: bs0;
                 pr2 := {| pr1 := hd0 :: tl0; pr2 := hd' :: tl0 |}
               |};
             pr2 := OnOne2All_hd P b bs0 hd0 hd' tl0 p e
           |} e0) = e0)


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