Can you prove that the script doesn't die? This is CGI, right? That being the case, your warning if the script dies will be a mysterious server error and an entry in the web server's error log. If it does die, you know the file never got opened in the first place. If your script has already printed the headers, it might be more difficult to find the error, because part of the page may still load. Perhaps using the CGI::Carp qw/fatalsToBrowser/; module will help you to see what's going on.

If the file never got opened in the first place, possible reasons might be that you're looking in the wrong directory for a file that might exist in some other path location. This can happen when using relative paths. Or you may be attempting to open a file that your script (executing as 'nobody') doesn't have permission to open.