Preheat oven to 350 degrees and line a shallow baking pan with foil.
In a small bowl whisk together maple barbecue sauce, ketchup, soy sauce, garlic, and honey. Put beef tenderloin in baking pan and coat with maple barbecue sauce mixture. Roast beef in middle of oven 35 to 40 minutes, or until a meat thermometer inserted in center registers 160 degrees. Cool beef completely in baking pan.
In a small bowl stir together sauce ingredients until brown sugar is dissolved.
Transfer beef to a cutting board and with a knife held at a 45 degree angle cut meat across grain into thin slices. Arrange beef, overlapping slices slightly. Spoon garlic sauce over beef and sprinkle pork with Japanese perilla leaves.