Question about persistance by checking and if not there inserting HTTP Header Field

Hello,

You can try with that one:

when HTTP_REQUEST {
    set clientip ""
    if { [HTTP::header exists True-Client-IP] } {
        set clientip [HTTP::header True-Client-IP]
    }
    else { 
        HTTP::header insert True-Client-IP [IP::client_addr]
        set clientip [HTTP::header True-Client-IP]
    }
    persist uie $clientip
}

Regards