Thaw shrimp, if frozen. In a medium bowl toss shrimp with flour until coated. Set aside.
For sauce, in a small bowl stir together wine, lemon juice, capers, salt, and pepper. Set aside.
Place margarine or butter in a wok or large skillet. (Add more margarine as necessary during cooking.) Preheat over medium-high heat until margarine is melted. Stir-fry garlic in margarine for 15 seconds.
Add half of the shrimp to the hot wok. Stir-fry for 2 to 3 minutes or until shrimp turn opaque. Remove shrimp from the wok. Repeat with remaining shrimp; remove all shrimp from the wok.
Stir sauce. Add sauce to the hot wok. Cook and stir until sauce is bubbly and reduces slightly. Return shrimp to the wok. Cook and stir about 1 minute more or until heated through. Serve immediately over rice.Garnish with lemon slices, if desired. Makes 4 servings.