Goal:
    A : Type  l : list A  l' : list A  H0 : 0 = 0  H : l = l'
  ============================
   (l = l')


DEBUG:Going to execute:
easy
DEBUG LTAC Evaluated term: app_nil_r
DEBUG LTAC Evaluated term: app_nil_r
DEBUG LTAC Evaluated term: app_nil_r
DEBUG LTAC Evaluated term: app_nil_r