Document contains no data is a pretty clear indicator that your program exited early. Like other have said, check your error logs, add the lovely use CGI::CARP qw(fatalsToBrowser); to hopefully get SOME data to the browser.

Also, if it's a basic perl script cgi try perl -cw filename.cgi and see if it complains about a simple error that might bomb it out.

I had this happen once with a 45kb script with scads of modules. I had -w and use strict; and CGI and Carp and all that jazz going, no errors in the log, no compile errors, nothin. After hours, literally, I noticed that I had absentmindedly put an exit(0); where a much more reasonable return(0); should have been. =) It happens...