Slice pork into strips about 2 inches long, 1 inch wide and 1/4 inch thick. Place in a bowl or sealable plastic bag, and add oyster sauce, 2 tablespoons sherry, sesame oil, garlic and red pepper flakes. Stir to coat well. Cover or seal, and allow to marinate at room temperature for 3 hours, or in refrigerator up to 24 hours.
Place a large wok or skillet over high heat, and add oil. Allow pan to heat for 1 to 2 minutes, then add pork and marinade. Toss meat until seared and no longer pink. Add scallions, corn and sugar snaps. Stir until sugar snaps turn bright green, about 1 minute.
Add bok choy and mushrooms, and stir constantly for about 1 minute. Add bean sprouts and remaining 1/4 cup sherry. Continue to stir until wine is almost evaporated. Transfer to a large platter, sprinkle with cilantro, and serve immediately.