Goal:
  
  A : Type
  B : Type
  C : Type
  D : Type
  E : Type
  P : E → A → Type
  Q : C → A → Type
  R : B → D → Type
  f : B → C → E
  b : B
  l : list B
  y : D
  l' : list D
  r : R b y
  hb : All2 R l l'
  ============================
   (∀ (H := CoreTactics.block) (x : C) (y : A) (l0 : list C) (l' : list A),
      Q x y
      → All2 Q l0 l'
        → #|l| = #|l0|
          → (∀ (x0 : B) (y0 : C) (z : A) (w : D),
               R x0 w → Q y0 z → P (f x0 y0) z)
            → (∀ (l : list B) (l''' : list D),
                 All2 R l l''' → #|l| = #|l0| → All2 P (map2 f l l0) l')
              → let H0 := CoreTactics.block in
                All2 P (map2 f (b :: l) (x :: l0)) (y :: l'))


DEBUG:Going to execute:
match goal with
           | |- let _ := CoreTactics.block in ?T =>
                 match T with
                 | context [ CoreTactics.block ] =>
                     change T; CoreTactics.intros_until_block
                 end
           | _ => CoreTactics.unblock_goal
           end