Goal:
  
  A : Type
  P : A → A → Prop
  a : A
  l : list A
  r : A
  r' : A
  IHl : ∀ (l' : list A) (r : A),
          Forall2 P (l ++ [r]) (l' ++ [r']) → Forall2 P l l' ∧ P r r'
  H : Forall2 P (a :: l ++ [r]) [r']
  H3 : P a r'
  H5 : Forall2 P (l ++ [r]) []
  ============================
   (Forall2 P (a :: l) [] ∧ P r r')


DEBUG:Going to execute:
destruct l

Goals:
  
  A : Type
  P : A → A → Prop
  a : A
  r : A
  r' : A
  IHl : ∀ (l' : list A) (r : A),
          Forall2 P ([] ++ [r]) (l' ++ [r']) → Forall2 P [] l' ∧ P r r'
  H : Forall2 P (a :: [] ++ [r]) [r']
  H3 : P a r'
  H5 : Forall2 P ([] ++ [r]) []
  ============================
   (Forall2 P [a] [] ∧ P r r')

  
  A : Type
  P : A → A → Prop
  a : A
  a0 : A
  l : list A
  r : A
  r' : A
  IHl : ∀ (l' : list A) (r : A),
          Forall2 P ((a0 :: l) ++ [r]) (l' ++ [r'])
          → Forall2 P (a0 :: l) l' ∧ P r r'
  H : Forall2 P (a :: (a0 :: l) ++ [r]) [r']
  H3 : P a r'
  H5 : Forall2 P ((a0 :: l) ++ [r]) []
  ============================
   (Forall2 P (a :: a0 :: l) [] ∧ P r r')


DEBUG:Going to execute:
cbn in *
DEBUG LTAC Evaluated term: l