In a small bowl, combine the brown sugar, vinegar, ketchup and soy sauce. Pour half into a large resealable plastic bag; add pork. Seal bag and turn to coat; refrigerate for 30 minutes. Set remaining marinade aside., Drain and discard marinade from pork. In a large skillet, cook pork in oil for 3 minutes. Add the onion, carrots, green pepper, garlic and ginger; saute until pork is tender. Add reserved marinade. Bring to a boil; cook for 1 minute. Stir in the pineapple. Serve with rice if desired. Freeze option: Cool pork mixture. Freeze in freezer containers. To use, partially thaw in refrigerator overnight. Heat through slowly in a covered skillet, stirring occasionally and adding a little broth or water if necessary. Serve over rice.