I think you are right, there is two "plot"s, but I never noticed till I add set_legend, take a look at this code.

#!D:\\tools\\Perl\\bin\\perl.exe
use CGI;
use GD::Graph::Data;
use GD::Graph::bars;
use GD;

  $q = new CGI;

  my $data = GD::Graph::Data->new();

  @data = ( [qw(Env)], [12] , [4]);

  # And we quickly need to do some manipulations on that
  my $data = GD::Graph::Data->new();
  $data->copy_from(\@data);

  my $chart = GD::Graph::bars->new();
  
  $chart->set_x_axis_font(gdMediumBoldFont);  # to display environment
  $chart->set_y_axis_font(gdMediumBoldFont); 
  $chart->set_title_font(gdGiantFont);
  $chart->set_x_label_font(gdGiantFont);
  $chart->set_y_label_font(gdGiantFont);

  $chart->set(x_label => "Environment" , 
            y_label => "count",
        title => "Migration count per environment",
        bar_spacing => 20,
        shadow_depth => 5,
        long_ticks => 0,    # this is for horizontal and vertical line
+s, 
        dclrs => [qw (lgreen lblue lred)], 
        show_values => 1
      );
  $chart->set_legend_font(GD::gdMediumBoldFont);
  $chart->set_legend("ACPT","PROD");
  ################### This is the code I just commented ###
  ### but even with this it was drawing only once. 
  # my $gd = $chart->plot($data);

 print $q->header('image/png');  
 binmode STDOUT;  
 print STDOUT $chart->plot(\@data)->png;
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Edited by planetscape - added code tags