876. The perfect subjunctive stem ends in #-erī-#, for which #-eri-# is
sometimes used (35, 2, 3): as,
#rēxeri-m#, #rēxerī-s#, #rēxeri-t#, #rēxerī-mus#, #rēxerī-tis#,
#rēxeri-nt#.
877. In the perfect subjunctive, long #ī# is found before the person
endings #-s#, #-mus#, and #-tis#, some 25 times, as follows: #-īs#, 18
times (Plaut. 3, Pac., Enn., Ter., Hor., Tib., Sen., inscr., once each,
Ov. 8), #-īmus#, 4 times (Plaut. 3, Ter. 1), #-ītis#, 3 times (Plaut. 2,
Enn. 1).
878. In the perfect subjunctive, short #i# is found, as in the future
perfect, some 9 times, thus: #-is#, 8 times (Plaut. in anapests 3, Verg.
2, Hor. 3), #-imus# once (Verg.). But before #-tis#, short #i# is not
found.