iRule to a variable for chosen pool member

i actually had to split the events to do the different things i needed.. i ended up with this-

when ACCESS_ACL_ALLOWED { 
    set user [ACCESS::session data get "session.logon.last.username"] 
    set uri [string range [HTTP::uri] 3 end] 
    HTTP::header replace "APP_USER" $user
        HTTP::uri $uri
    }
when HTTP_REQUEST_SEND {
    if { [class match [LB::server addr] equals server-dev] } {
        clientside {
            HTTP::header replace Host "[class match -value [LB::server addr] equals server-dev]:9000"
            }
        }
    }   
when HTTP_RESPONSE {
    if { [HTTP::header "Location"] starts_with "devserver" } {
    HTTP::header replace Location [string map {"[class match -value [LB::server addr] equals server-dev]:9000" "company.domain.com/app"} [HTTP::header value Location]] }
}

Thanks for your valuable input on this..