XF 1.3 RegEx Username Validation?

[Hentai]

I run a music community and one of our forum rules is you are not allowed to end your username with a capital "P". The rule may seem strange to outsiders but we implemented it because people were misusing the honorific "-P" (standing for "Producer") and it had lead to drama in the past.

Is there any way I can enforce this rule with RegEx or the "Disallowed Text in User Names" function?

 

[Mike]

The regex is always case insensitive, so you could only prevent "P" and "p" as the last letter. (That would be done with: [^P]$ )