Do they differ slightly or is it just different pronunciations, cuz the example sentences pleco gives are identical.
#whats the difference between 完了（wanliao）and 完了（wanle）
vital salmon
tight parrot
No difference.
了(liao) means end, so does 完. So 完了(liao) still means end.
I only heard this in some Peking operas. I think it is a way to stretch the sound because了(le) is too short to sing.
uncut patrol
wanliao is a somewhat formal intransitive verb meaning to finish/end
wanle is a transitive/intransitive verb phrase meaning "to have finished"
since the le particle can be omitted a lot of the time without altering the meaning, and wan/wanliao mean the same thing, there's often little difference
in singing, le is usually pronounced liao, in which case both uses are pronounced the same
(because le historically developed as a reduced version of liao, and music preserves the nondistinction for melodic reasons)