The first thing that strikes me about your Perl program is that it uses a very ill-advised method of parsing the CGI parameters.

I suggest that you remove all the "DO NOT EDIT" code with this:

use CGI qw/:standard/;
foreach (param()) {
  $INPUT{$_}=param($_);
}
[download]

Before you replace that, (and test how it works) I don't even want to look at the rest of the code.