So possibly but I actually don’t care if the substring exists in the middle. I am more so determining the ending. So for example on our site this would be the case:
John_company != allowed
john_companyAsdf == allowed
john_company_john == allowed
So I don’t necessarily mind if the substring exists in the begining or middle or if there are different variations it is more so ensuring users cannot use our identifier at the end of a username.