It is possible that you are not printing the http header early enough. Try adding a line to print that header again for debug purposes right at the top of your program.

Perhaps you are having trouble including a module or you have a BEGIN block or other initial processing which dies with an error message (when the browser is expecting an http header). Carp is good, but why not first try running it from command line or from browser with that extra header being printed at the beginning. Then you can add print statements as milestones to tell you where your program has gone.

If this fails also check permissions, try chmod 755 yourscript.cgi also make sure your apache can execute as cgi files with the extension (.pl or .cgi) which you have decided to use. Oh and also make sure you are running perl 5 (type perl -V).