use Chart::Plot; 
    my $img = Chart::Plot->new; 
    my @data = qw( 10 11 11 12 12 13 13 14 14 15);
    $img->setData (\@data);
    

    # draw circles around each data point, diameter 15 pixels
    my $gd = $img->getGDobject;
    my $blue = $gd->colorAllocate(0,0,255); # or use $img's blue 
    my ($px,$py); 
    for (my $i=0; $i<$#data; $i+=2) {
      ($px,$py) = $img->data2pxl ($data[$i], $data[$i+1]);
      $gd->arc($px,$py,15,15,0,360,$blue);
    }


    # draw the rest of the chart, and print it 
    open (OUT,">plot.gif"); 
    binmode OUT; 
    print OUT $img->draw(); 
    close OUT;