Goal:
  
  A : Type
  P : A → A → Type
  a : A
  l : list A
  r : A
  r' : A
  IHl : ∀ l' : list A, All2 P (l ++ [r]) (l' ++ [r']) → All2 P l l' × P r r'
  X : All2 P (a :: l ++ [r]) ([] ++ [r'])
  X0 : P a r'
  X1 : All2 P (l ++ [r]) []
  ============================
   (All2 P (a :: l) [] × P r r')


DEBUG:Going to execute:
destruct l

Goals:
  
  A : Type
  P : A → A → Type
  a : A
  r : A
  r' : A
  IHl : ∀ l' : list A,
          All2 P ([] ++ [r]) (l' ++ [r']) → All2 P [] l' × P r r'
  X : All2 P (a :: [] ++ [r]) ([] ++ [r'])
  X0 : P a r'
  X1 : All2 P ([] ++ [r]) []
  ============================
   (All2 P [a] [] × P r r')

  
  A : Type
  P : A → A → Type
  a : A
  a0 : A
  l : list A
  r : A
  r' : A
  IHl : ∀ l' : list A,
          All2 P ((a0 :: l) ++ [r]) (l' ++ [r'])
          → All2 P (a0 :: l) l' × P r r'
  X : All2 P (a :: (a0 :: l) ++ [r]) ([] ++ [r'])
  X0 : P a r'
  X1 : All2 P ((a0 :: l) ++ [r]) []
  ============================
   (All2 P (a :: a0 :: l) [] × P r r')


DEBUG:Going to execute:
inversion X1
DEBUG LTAC Evaluated term: l