Bad script with lots of false positives. For .nl domains for instance, you must query it with whois and grep for "name.nl is free".

Just because there are no DNS records doesn't mean the domain is free.

I ran the script for a while and apparently these are available:

bjc.de caw.de cqk.de ctf.de eqn.de fab.de hwj.de iwy.de myd.de

I stopped it after that.

And that's the story behind xkcd.com -- one of very last available 4-letter domains in .com zone back then.

3: Syntax error: "(" unexpected

???