.... as to your line 23 problem, it may be an if-elsif-else logic problem

...try commenting out all your logic, and try just

if ($ENV{'REQUEST_METHOD'} eq 'POST'){   print "success\n"      }
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...these lines of yours look particularly odd, as far as possible logic and prescendence errors

 elsif ($ENV{'REQUEST_METHOD'} eq 'POST') {
        if ($ENV{'CONTENT_TYPE'}=~ m#^application/x-www-form-urlencode
+d$#i) {
            $ENV{'CONTENT_LENGTH'}
                || &HTMLdie("No Content-Length sent with the POST requ
+est.") ;
            read(STDIN, $in, $ENV{'CONTENT_LENGTH'}) ;

        } else {
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its too early sunday morning for me to test that logic out.... but that is where i would look first