Regex negation?

Question

I\'m playing Regex Golf (http://regex.alf.nu/) and I\'m doing the Abba hole. I have the following regex that matches the wrong side entirely (which is what I was trying to

Answer 1

Using the explanation here: https://stackoverflow.com/a/406408/584663

I came up with: ^((?!((\w)(\w)\4\3)).)*$