Since you can't run the script on the command-line (not sure why), and you most likely will get other syntax errors in the future, you might like to add near the top of your script (after the #! line):

use CGI::Carp qw(fatalsToBrowser);
[download]

This will send error messages to the browser so you can see them. You probably don't want that in production.
You error is that you need $num = ""; or just my $num;