(This is not Cyperus at all) herbarium specimen which seems doubtful. Collection spot was southern part of West Bengal (District: 24 paraganas).
It seems to have longer and more numerous super-inflorescences (18-25cm) than Eleusine indica. The appearance is somewhat like Achrachne racemosa, but again, not clear. Some Digitaria species also have a similar comparable morphology, could it be one of those? Please try to help with the identification.