Try this (produces this):

use Data::Dump qw[ pp ];
use GD::Graph::bars;
use GD::Graph::hbars;

my @data = (
    [ qw[Jan _ Feb _ Mar _ Apr _ May _ Jun _ Jul _ Aug _ Sep _ Oct _ N
+ov _ Dec _ ] ],
    [ map rand( 25 ), 1 .. 24 ],
    [ map rand( 25 ), 1 .. 24 ],
);

for my $my_graph (GD::Graph::hbars->new( 800, 600 ) ) {

    $my_graph->set(
        title => 'Stacked Bars (incremental)',
        x_label => 'X Label', y_label => 'Y label',
        cumulate => 1,
        overwrite => 1,
        borderclrs => $my_graph->{dclrs},
        bar_spacing => 20,
        bar_width => 10,
        transparent => 0,
    );

    $my_graph->set_legend( qw(offset increment more));
    $my_graph->plot(\@data);
    save_chart($my_graph, "test.png");
}
system 1, 'test.png';



sub save_chart
{
    my $chart = shift or die "Need a chart!";
    my $name = shift or die "Need a name!";
    local(*OUT);

    open(OUT, ">$name") or
        die "Cannot open $name.$ext for write: $!";
    binmode OUT;
    print OUT $chart->gd->png;
    close OUT;
}
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