Perfect inferential is used for events or actions completed in the past at a time not specified, or if specified,
still outside of the period of time of current relevance to the speaker,
and expresses that the knowledge of the fact is inferred from evidence,
be it sensorial perception, logical deduction or direct report from a trusted source.
That knowledge is most often presented as new information, sometimes unexpected, for the speaker himself.
The knowledge might be inferred from sensorial perception:
Karim qishloqqa ketmagan ekan.
Karim has/had obviously not gone to the village.
The knowledge might be inferred from logical deduction:
Poyezd ketib qolgan ekan.
It looks like that the train has/had already left.
The knowledge might be obtained from a direct report from a trusted source:
Ular Pamir tog'iga chiqqan ekanlar.
It appears that they have climbed the Pamir mountains.
The event or action may still have current relevance (perfect value):
He (apparently) went away.
Apparently, you have not gone.
Men bu filmni ko'rgan ekanman.
It seems that I have seen this film.
The event or action may have occurred in the distant past, or prior to a past time of reference.
See also the contrast with the indirective past in the second example.
Siz bu kitobni o'qigan ekansiz.
It looks like you had read this book.
Karim og'zaki imtihondan qoniqarli baho olibdi, lekin yozma imtihondan qoniqarsiz baho olgan ekan.
(they said that) Karim got a good mark at the oral exam, but he had got a bad mark at the written exam.