With a large sharp knife, chop the chilies very fine. Mince the garlic. Coarsely chop the tomatoes and white onion. Finely chop the scallions and cilantro. Place the garlic, tomatoes, scallions, and cilantro in a large bowl. If the tomatoes are very dry and juiceless, gradually add up to 1/2 cup cold water to achieve a light salsa consistency. Stir to mix the ingredients. Add the chiles a little at a time, tasting, until it is as hot as you like. Add the oregano, then squeeze the lime juice into the salsa; gradually add salt to taste. Use at once. This recipe yields about 5 cups of salsa.