The affix kyap is optionally used after the verb sṛj 'to cleanse'.,
This is an example of Prapta-vibhasha. By rule 110 ante, the root मृज् having a penultimate ऋ would have necessarily taken kyap; this sutra declares an option. As परिमृज्यः or परिमार्ग्यः 'to be cleansed'. The second form is thus evolved:-
परिमृज्य + ण्यत् (III. I. 124) = परिमृग् + य 7.3.52 = परिमार्ग्य 7.2.114,