TCL 1st class

set ns [new Simulator]
set f [open out.tr w]
$ns trace-all $f
proc finish { } {
    global ns f
    $ns flush-trace
    close $f
    exit 0
    }
set n0 [$ns node]
set n1 [$ns node]
$ns duplex-link $n0 $n1 1mb 10ms DropTail
$ns at 5.0 "finish"
$ns run