[1] Comparable material in other lexica; references at Photius pi737 Theodoridis, where the headword is peri/pleon and Theodoridis opines that the Suda compiler has made the change to peri/plewn on his own initiative (suo Marte). The primary headword is (to judge by the gloss) masculine accusative singular; the secondary headword is masculine nominative singular.
As the accentuation shows, these forms result from "quantitative metathesis," the original stem having a long vowel as in pi/mplhmi.