Presistence profile

Would something like this work. Would it persist if the token remains the same? and if this value was to change would it create a new persistence record?

when HTTP_REQUEST { collect the payload containing the POST data HTTP::collect [HTTP::header SecurityTokenReference] } when HTTP_REQUEST_DATA { persist on data from 11th character following 'URI=' up to "<" and follow existing persistence record or create a new one persist uie [findstr [HTTP::payload] "URI=" 11 "<"] }

Any assistance would be greatly appreciated.