use strict;
use warnings;
use GraphViz;
use CGI;

my $q = new CGI();
print $q->header(), $q->start_html();

open my $dot, ">", "tree.dot" || die $!;
print $dot qq(digraph g { graph [] A -> B; C -> B; });
close $dot;

my $cmd = "dot -Tgif tree.dot -o tree.gif";
system($cmd);

print $q->end_html;