Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
compĕrĭor (conp-), īri, pertus sum, 4, v. dep., collat. form of comperio, q. v., to ascertain, learn, obtain certain knowledge that, etc. (rare); constr. mostly with acc. and inf.: dum ne ab hoc me falli comperiar, Ter. And. 5, 3, 31; Sall. J. 45, 1; 108, 3; Tac. A. 4, 20; Gell. 3, 3, 1: quid comperior? App. M. 2, p. 124, 11; perf., Tert. adv. Herm. 28.