Mine

...
    for {set z 0} {$z<$dataresult} {incr z} {
        set dataresult2 [mysqlnext $handle]

        set data_id [lindex $dataresult2 0]
        set oid [lindex $dataresult2 1]
        set name [lindex $dataresult2 2]
        set color [lindex $dataresult2 3]
        set data_type [lindex $dataresult2 4]

        set connections [Tnm::snmp value [$s get "$oid" ] 0]

        puts -nonewline "$name\t"
        puts $connections
        append rrdstring ":$connections"
        append createcommand "DS:$name:$data_type:1200:0:1000 "
    }
    set createcommand [string trimright $createcommand " "]

    set rrd_dir /var/www/klammeraffe/css-rrd
    set rrd_path $rrd_dir/css-$device_id.rrd

    if { ! [file exists $rrd_path] } {
        puts "Making rrd $rrd_path"
        puts $createcommand
        puts "\n\n"

        set command "Rrd::create ${rrd_path} -b N --step 60 $createcommand RRA:AVERAGE:0.5:1:105120"

        $command

        #if { [catch {Rrd::create $rrd_path -b N --step 60 $createcommand RRA:AVERAGE:0.5:1:105120} result ] } {
        #   puts "Error: $result"
        #}
    }
...