From the looks of things, you'll want to familiarise yourself with some of the modules bundled with Perl that can make your life a lot easier. For example, if you need to make a directory, you can use File::Path:

use File::Path;

# ...

unless (-d $upload_dir)
{
     mkpath($upload_dir);
}
[download]

You will note, though, that this is pretty bold, taking a parameter in from the CGI input and making a directory based on that name. You should take great care to make sure that this directory name is valid, and, for example, doesn't contain values like "../../../.w4r3z/"

Instead of cranking open something like Sendmail directly, try using Mail::Sender or Mail::Mailer which give you a simpler interface.

Most important, of course, is to use strict which is not optional if you want to do things properly. Yes, you have to declare your variables, each and every one of them, but this shouldn't be considered bad.

If you could post the error you're getting, that might help with diagnosis.