Quickly verify a large number of domains via whois

If I do time whois google.com it takes about a second to come back with a response to if a domain is registered or not. If I do (a non-existant domain) time whois fslafdjlsadjflsjdf.com It comes back very quickly. I want to be able to query several thousand domains to verify if they are registered or not (just a simple true/false) and I want to do it quickly. What is the best way to do this? The fact that the failure comes back so quickly seems to suggest there is something that will give back quick negatives.