Ok, first a tip, try running your script from the command line, examples of both tests: 
$ REQUEST_METHOD=GET QUERY_STRING='bob=jack&jane=janice' ./sendit.pl 
$ REQUEST_METHOD=POST CONTENT_LENGTH=20 ./sendit.pl <<EOF
bob=jack&jane=janice
EOF

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Second, I have to admit that my fellow monks are correct, with their suggestion that you should use the CGI module, and should definately not allow unauthenticated users unchecked access to your mailserver, as it will quickly be overcome with spammers. But unfortunately, your bug wouldn't be fixed by either of their solutions, so I'll continue with the analysis. When I ran my tests, I got an error from perl which is causing your 500 error: 
Undefined subroutine &main::LMAIL called at ./test.pl line 23.

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Incidently, those error messages will also appear in your webservers error logs. If I look at line 23, I can see: 
22:  open (LMAIL, "|usr/sbin/sendmail -t");
23:  print LMAIL("To: $in{myEmail}\n");
24:  print LMAIL ("From: $in{Email}\n");

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Notice the lack of a space between the filehandle LMAIL and your open parenthesis? Perl is interpreting that instance of LMAIL as a call to the function &LMAIL(), which doesn't exist. This is causing it to exit with the error printed above. Putting a space in there should fix your problem. Incidently, you'll also need one of those spaces on line 28 :)

   [ qi3ber ] I used to think that I knew it all, then I started to listen.

In reply to Re: form mail with post, getting "premature ending of script headers" by qi3ber
in thread form mail with post, getting "premature ending of script headers" by edahm

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