This is just a small and nice script that you can use for finding any free domain in certain TLD with characters specified in regex.
Works based on assumption that no SOA record == domain doesn’t exists (can mean also broken stuff in nameservers) and only after that performs a whois lookup for faster search.
Domains are currently generated by regex in variable ‘combinations’ and output prints into console. Current setting equals exactly 3 letter .fi domains, with a-z characters.