Goal:
  
  A : Type
  H : ReflectEq A
  a1 : A
  l1 : list A
  a2 : A
  l2 : list A
  prefix : list A
  l1' : list A
  l2' : list A
  Heq : split_prefix l1 l2 = (prefix, l1', l2')
  ============================
   ((∀ (H := CoreTactics.block) (l3 l4 : list A),
       {| pr1 := l1; pr2 := l2 |} = {| pr1 := l3; pr2 := l4 |}
       → split_prefix l1 l2 = split_prefix l3 l4
         → let H0 := CoreTactics.block in
           let
           '(prefix, l1', l2') := split_prefix l3 l4 in
            l3 = prefix ++ l1' ∧ l4 = prefix ++ l2')
    → (a1 == a2) = true
      → ∀ (H := CoreTactics.block) (l3 l4 : list A),
          {| pr1 := a1 :: l1; pr2 := a2 :: l2 |} = {| pr1 := l3; pr2 := l4 |}
          → (a1 :: prefix, l1', l2') = split_prefix l3 l4
            → let H0 := CoreTactics.block in
              let
              '(prefix, l1', l2') := split_prefix l3 l4 in
               l3 = prefix ++ l1' ∧ l4 = prefix ++ l2')


DEBUG:Going to execute:
intro || (let H := fresh in
                     intro
                     H)
DEBUG LTAC Evaluated term: ((a1 == a2) = true
                            → ∀ (H := CoreTactics.block) (l3 l4 : list A),
                                {| pr1 := a1 :: l1; pr2 := a2 :: l2 |} =
                                {| pr1 := l3; pr2 := l4 |}
                                → (a1 :: prefix, l1', l2') =
                                  split_prefix l3 l4
                                  → let H0 := CoreTactics.block in
                                    let
                                    '(prefix, l1', l2') := 
                                     split_prefix l3 l4 in
                                     l3 = prefix ++ l1' ∧ l4 = prefix ++ l2')
DEBUG LTAC Evaluated term: Prop