I think that this is what you were looking for. You were missing the save_chart sub, and the script saves the chart as a gif (by default):

#!/usr/bin/perl 

use strict;
use warnings;
use GD::Graph::bars;
use GD::Graph::hbars;
use GD::Graph::Data;

my $data = GD::Graph::Data->new([
   ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug",
   "Sep", "Oct", "Nov", "Dec"],
   [23, 5, 2, 20, 11, 33, 7, 31, 77, 18, 65, 52]]);

my $mygraph = GD::Graph::bars->new(500, 300);
$mygraph->set(
    x_label     => 'Month',
    y_label     => 'Number of Hits',
    title       => 'Number of Hits in Each Month in 2002',
) or warn $mygraph->error;

$mygraph->plot($data) or die $mygraph->error;
save_chart($mygraph, 'test');

sub save_chart { 
    my $chart = shift or die "Need a chart!"; 
    my $name = shift or die "Need a name!"; 
    local(*OUT); 
    
    my $ext = $chart->export_format; 
    open(OUT, ">$name.$ext") or die "Cannot open $name.$ext for write:
+ $!"; 
    binmode OUT; 
    print OUT $chart->gd->$ext(); 
    close OUT;
}
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Note that my @data = ([ should be

my $data = GD::Graph::Data->new([
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Updated: Noticed something missing? Here's the corrected chart:

#!/usr/bin/perl 

use strict;
use warnings;
use GD::Graph::bars;
use GD::Graph::hbars;
use GD::Graph::Data;

my $data = GD::Graph::Data->new([
   ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug",
   "Sep", "Oct", "Nov", "Dec"],
   [23, 5, 2, 20, 11, 33, 7, 31, 77, 18, 65, 52]])
or warn GD::Graph::Data->error;

for my $mygraph (GD::Graph::bars->new(500, 300), 
                 GD::Graph::hbars->new(500, 300)
{
    my $name = 'test';
    print STDERR "Processing $name\n";

$mygraph->set(
  x_label      => 'Month',
  y_label      => 'Number of Hits',
  title        => 'Number of Hits in Each Month in 2002',
  bar_spacing  => 8,
  shadow_depth => 4,
  shadowclr    => 'dred',
  transparent  => 0,
)
or warn $mygraph->error;

$mygraph->plot($data) or die $mygraph->error;
save_chart($mygraph, $name);
}

sub save_chart { 
    my $chart = shift or die "Need a chart!"; 
    my $name = shift or die "Need a name!"; 
    local(*OUT); 
    
    my $ext = $chart->export_format; 
    open(OUT, ">$name.$ext") or die "Cannot open $name.$ext for write:
+ $!"; 
    binmode OUT; 
    print OUT $chart->gd->$ext(); 
    close OUT;
}
[download]