I beg your pardon.
I bought a package of extensions with advertised functionality that in this case does not work.
The last time I messed with Regular Expressions I actually paid for a custom solution from WebAssist and when it was pointed out later that the expression does not work in all cases I was told that it was my problem. Check my support history.
I'm pretty sure that I am not the only client working on websites that may be visited by people with 1 letter domains. Perhaps WebAssist's time might be better spent fixing the problem with the extension rather than posting links to other web pages.