Cut pork into cubes and eliminate excess fat. In a mixing bowl, season pork with garlic, salt, pepper and oregano. In a large skillet or wok preheated with olive oil, sear meat on all sides. Turn heat down and add wine to deglaze skillet and incorporate caramelized juices and seasoning from bottom of pan by folding them with meat using spoon. Add tomatoes and leeks. Remove from heat after five to seven minutes.