Metronome

func metronome (beats_per_minute = 72, beats_per_bar = 4) {

    var counter   = 0
    var duration  = 60/beats_per_minute
    var base_time = Time.micro+duration

    STDOUT.autoflush(true)

    for next_time in (base_time..Inf `by` duration) {
        if (counter++ %% beats_per_bar) {
            print "\nTICK"
        }
        else {
            print " tick"
        }
        Sys.sleep(next_time - Time.micro)
    }
}

say metronome(ARGV.map{ Num(_) }...)

Output:

% sidef metronome.sf 60 6

TICK tick tick tick tick tick
TICK tick tick tick tick tick
TICK tick tick tick tick tick
TICK tick tick tick tick tick
TICK tick tick tick tick tick
TICK tick tick tick tick tick
TICK tick tick tick^C