Greetings all,
I would suggest splitting out your graph creation into its own script that prints its own header and displays your graph... then you can embed it in your html with an image tag.
example
Your script for creating the graph

#!/usr/local/bin/perl -w
use strict; #ALWAYS!!!!

use GD::Graph::pie;

my @data = (['A','O','S','I'],[3,16,12,47]);

my $mygraph = GD::Graph::pie->new(200, 200);
my $myimage = $mygraph->plot(\@data)->png;
print "Content-type: image/png\n\n";
print $myimage;
exit;
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The image tag to embed in your HTML output.

<img src="your/script/here.cgi?key=value(if needed)">
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rather than

<img src=$myimage>
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This is actually what I do when I am displaying binary data from a database Blob field.
Hope that helps. Let me know if you have any questions.

-injunjoel