How to limit http request rate

This one works! when HTTP_REQUEST {

set lrqst 10
set ltime 10
set rtime 5
if {[table lookup -notouch -subtable "blacklist" [HTTP::uri]] != "" }{
    reject
    log local0.warn "reject"
}
elseif { [table lookup -notouch -subtable "clientxdlist" [HTTP::uri]] == "" }{
    table set -subtable "clientxdlist" [HTTP::uri] 1 indefinite $ltime
}
elseif { [table lookup -notouch -subtable "clientxdlist" [HTTP::uri]] < $lrqst}{
    table incr -subtable "clientxdlist" [HTTP::uri]
}
else {
    table set -subtable "blacklist" [HTTP::uri] 1 indefinite $rtime
}

}