JSON Web Token (JWT) Parser

Thanks GRaham. My intension is to write a basic iRule which will validate allow user to web service if comoddo certificate is available(Installed on browser) or allow request to web service if Authorization http header containing JWT token is available. I need to basically validate age of the token from exp param

Sample decrypted JWT Token: {"sub":123456789,"tkid":12345,"term":123456789,"exp":1548159789,"int":10}

Can you suggest basic iRUle to validate Authorization for exp time.