Combine the soy sauce, oil, sugar, sherry, vinegar, garlic, ginger and red pepper flakes, and stir until the sugar dissolves. Transfer to a resealable plastic bag and add the pork tenderloin. Seal the bag and marinate the pork in the refrigerator, turning once, for 1/2 hour, or up to 8 hours.
Preheat the broiler. Place the pork on a roasting pan and broil for 15 minutes, turning once.