iRule - select rate class based on source IP match in data group

when HTTP_REQUEST {
 Compare the request source IP with the addresses in the thoseclasses data group
 and populate the variable 'thatclass' with the associated string value if
 there is a match
  set thatclass [class match -value [IP::client_addr] equals thoseclasses]
   As long as our variable: thatclass isn't empty, continue
   if { $thatclass ne "" } {
    Apply the rateclass
    rateclass $thatclass
   }
   If there wasn't a match and variable 'thatclass' is empty, use a default
   else {
    rateclass CatchAll
  }
}