<%perl>

use GD::Graph::bars;
use Data::Dumper;

my ($x, $y, @numbers, $number);

my @data = (
    # X axis
    [ qw( -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 )]
);

# loop for each success level
for ($x = 1, $x < 5, $x++){

    # generate numbers for each skill level
    for ($y = 1, $y < 19, $y++){

        $number = $x*$y*2+5;
        push @numbers, $number;
    }
    push @data, [@numbers];
}

my $graph = new GD::Graph::bars();
$graph->set(
    title       => 'Skill Resolution',
    x_label     => 'Skill Level',
    y_label     => 'Success Level'
);

my $gd = $graph->plot(\@data) or die "Could not plot: ".$graph->error.
    Dumper(@data);

print "Content-type:  image/png\n\n";
print $gd->png();

</%perl>