whois bulk queries, how to

[BLS]

Hi I want to do bulk queries on whois engines. Everthing works fine for 
a single request. whois("suneido.com") for instance. The problem is that 
the whois servers  are disconnecting after 1 request. I know about a few 
desktop whois apps which are able to do bulk queries..
Questions is what is the big trick ? This seems to be a good kept 
secret. Any ideas ?
Bjoern