My advice is to break down the problem into small junks which you can understand. First, see if you can create a GD graph manually with your data, then if successful, see if your object output is suitable for input to GD::graph.

GD graph has some nested arrays it uses for input, for example, see how the data is arranged in the following example. Make sure your input is like that.

#!/usr/bin/perl -w
use strict;
use GD::Graph::bars;

my @data = ( [qw(a b c d e f g)], [1,2,3,4,5,6,7] );

my $graph = GD::Graph::bars->new(200, 200);
$graph->set(
   transparent       => '0',
   bgclr             => 'lgray',
   boxclr            => 'white',
   fgclr             => 'white',
   cycle_clrs        => '1',
   x_label           => 'X Label',
   y_label           => 'Y label',
);

my $gd = $graph->plot(\@data);
binmode STDOUT;

#print "Content-type: image/png\n\n";
print $gd->png();
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