If you're running this as a CGI program (as your use CGI would imply), I fail to see where you are printing the appropriate CGI header. Add

print $query->header, $query->start_html("some title");
[download]

before the rest of your program.

And get a monkname! They're free, or rather, at least half price this week! It's hard to be motivated to answer a transient. {grin}