1 to 1 1/2 pounds cooked shrimp, peeled and deveined
1/2 cup each lemon juice, lime juice, orange juice
1 small onion, finely chopped
1 scallion (spring onion) green and white parts, finely
chopped
1 tomato, peeled, seeded, and chopped
1/4 cup chopped cilantro or parsley
Finely chopped red or green hot chile pepper, to taste
Salt and freshly-ground pepper, to taste
2 to 3 avocados, halved and pitted (optional)