Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
pervinca, v. vinca pervinca.
vinca pervinca (also in one word, vincapervinca), ae, f., a plant, periwinkle, Plin. 21, 11, 39, § 68; 21, 27, 99, § 172; called also simply pervinca, App. Herb. 58.