Goal:
  
  A : Type
  H : ReflectEq A
  l1 : list A
  l2 : list A
  l : list A
  ll1 : is_prefix (rev l) (rev l1)
  ll2 : is_prefix (rev l) (rev l2)
  _a_ : list A
  _b_ : list A
  _b1_ : list A
  ============================
   (is_prefix (rev l) _a_ → is_prefix (rev l) _a_)


DEBUG:Going to execute:
done
DEBUG LTAC Evaluated term: rev_invol
DEBUG LTAC Evaluated term: rev_invol
DEBUG LTAC Evaluated term: Prop
DEBUG LTAC Evaluated term: Prop