Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
per-mīrus, a, um, adj., very wonderful (class.): ut mihi permirum videatur, quemquam exstare, etc., Cic. Div. 2, 47, 99: illud vero mihi permirum accidit, fuisse, etc., id. Fam. 3, 10, 5.
In tmesi: per mihi mirum visum est, Cic. de Or. 1, 49, 214.