One of the following should be helpful:
   a)Running the script from the command line.
   b)Checking the server error log.

Update:
Following crazyinsomniac's suggestion here's a slightly different take on some good stuff to include near the top of your script

use CGI::Carp;
use CGI::Carp qw(fatalsToBrowser);
local $SIG{__WARN__} = \&Carp::cluck;
[download]

I'm using fatalsToBrowser already.

But what about suggestions a) and b)?

Perhaps my "should be helpful" was a little too casual. Those are not throw-away suggestions. They are likely the two most common and effective strategies for solving the kind of problem you describe. If you peruse the archives here at Perl Monks you will see them recommended again and again.

They will likely lead you to a solution to your current problem. And checking those two things should become second nature for you any time you have a problem of this sort because they are such reliable strategies.

In particular, find out where your server error log is and befriend it. It is one of your most reliable resources for debugging CGI.

Try "Content-Type: text/html\n\n";
Note capital 'T' for 'Type'. Good luck.

Apache (on both Linux and Windows) is happy to accept each of the following:

Content-type: text/html
Content-Type: text/html
CoNtEnT-TyPe: text/html
[download]

The original poster does not mention which server is being used. I can't find a definitive word on capitalization on HTTP headers but the HTTP docs I can lay my hands on seem rather casual about capitalization. YMMV

 
___crazyinsomniac_______________________________________
Disclaimer: Don't blame. It came from inside the void
perl -e "$q=$_;map({chr unpack qq;H*;,$_}split(q;;,q*H*));print;$q/$q;"

So, the script actually works, but the output cannot be printed out? Could that be that the script does not run twice? This often happens on modern javascript-laden ebusiness sites, where you can't use the Back button of your browser, lest some cooky is dropped from the jar or the session manager looses its way in the fog.

I haven't seen the script though, but some browsers reload the page when they print it out. If your script cannot be run twice in a row, you're doomed.

HTH

--bwana147

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).

Another really important possible source of information is your server logs. what do they say? anything? i just debugged something by spending an hour pulling my hair out and smashing my head against a wall and then 30 seconds reading the logfile and fixing the problem it told me about.

if you're running apache on a unix system, they're likely at /var/log/httpd-error.log or something like it.

Try the CGI::Debug module. I've used this module a few times and found it very helpful. If your script causes an error, CGI::Debug appends debugging information to the output so that instead of a very unhelpful "it didn't work" message, you usually end up with enough information to fix the problem. You can even have CGI::Debug send its output to you via e-mail, if you wish.