Cut tenderloin into 8 pieces; place each piece between two pieces of waxed paper and flatten. Sprinkle with lemon pepper. Melt butter in a large skillet over medium heat; cook pork for 3 to 4 minutes on each side or until no longer pink and juices run clear. Remove to a serving platter and keep warm. To the pan juices, add lemon juice, Worcestershire sauce and mustard; heat through. Pour over pork and sprinkle with parsley. Serve immediately.