In a large saute pan over medium heat, add the olive oil and onions. Cook until the onions are beginning to caramelize, 3 to 4 minutes, then add the garlic and cook for 2 minutes longer. Add the sherry and reduce for 2 minutes. Add the squid, parsley, oregano, lemon juice, salt, pepper, and pimento. Cook until the squid is tender, 5 to 6 minutes.