Helper for negative look-ahead. How?

https://stackoverflow.com/questions/26771592/negative-look-ahead-in-go-regular-expressions https://betterprogramming.pub/demystifying-look-ahead-and-look-behind-in-regex-4a604f99fb8c

Generate composite?

NotText("hello")
// (?:[^h]|h[^e]|hel[^l]|hell[^o])