Look in your Web server logs. That's where these errors will show up.
CGI::Carp will make errors show up in your browser, but generally not compile-time errors.
If you can't get to your Web server logs, try wrapping your CGI script in a small wrapper that will send errors to the browser. For example, if your CGI program is called dosomething, name this shell script dosomething-debug, make it executable, then run this script from your browser to see errors.