Goal:
  
  A : Type
  P : A → A → Type
  a : A
  l : list 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'
  ============================
   (All2 P (a :: l ++ [r]) (l' ++ [r']) → All2 P (a :: l) l' × P r r')


DEBUG:Going to execute:
<coq-core.plugins.ltac::intro@1> $1