ADFS custom claims append using criteria using if condition

Hi All,

We have an requirement to send SamAccountName as claim for an application & that's easy, but the problem is application accepts more than 4 characters as nameID. to over come this I was planning to append SamAccountName of persons with lessthan 4 characters& add prefix some character to it like a or x, so that any username which is like abc or xyz is changed to xabc ot axyz instead of making change in AD as this will be a big impact. so I am seeking help from the experts here on how or if possible to provide a custom claim using REGEX through which I can achieve this.

Thanks in Advance.

-Arvind Sindhu Enterprise Arch (Microsoft Technologies) Sapient.