iRule for URL Re-write

Given the following data group, if found replace one with two
class urlrewrite  {
   "apples.com oranges.com"
   "foo.com bar.com"
   "peas.com carrots.com"
}
when HTTP_REQUEST {
    set entry [findclass [HTTP::host] $::urlrewrite " "]
    if {$entry != ""} {
        log "Entry not null, replacing Host: [HTTP::host] with: $entry"
        HTTP::header replace Host $entry
    }
}