In a large shallow dish combine well the flour, the oregano, the salt, and the pepper and dredge the beef in the flour mixture, patting the flour onto the beef. In a large ovenproof skillet heat the oil over moderately high heat until it is hot but not smoking and in it brown the beef. Pour 1/4 cup of the vinegar over the beef, add the broth and 1 cup water, and bring the liquid to a boil. Braise the beef, covered, in a preheated 325° F. oven for 1 hour and 15 minutes, or until it is tender. Let the beef cool in the cooking liquid, transfer it with tongs to a cutting board, and discard the bones and fat. Skim the fat from the cooking liquid and stir in the garlic. In a small bowl combine the cornstarch, the remaining 2 teaspoons vinegar, and the Worcestershire sauce, stirring until the mixture is smooth, stir the mixture into the cooking liquid, and bring the liquid to a boil, stirring. Add the beef to the sauce, cook it over moderate heat for 10 minutes, or until it is heated through, and keep it warm. In a large saucepan of boiling salted water cook the orzo for 10 minutes, or until it is just tender, drain it, and in a bowl toss it with the dill. Serve the pot roast with the orzo. Serves 4 to 6. BEEF 10