in reply to no server response required
(I am taking for granted that the OP is addressing a Perl-based CGI or FastCGI handler ... therefore, that the question is being asked in an appropriate venue.)
It is my understanding that requests issued, at least to Apache, must be replied-to. You might be able to use a different HTTP server, but actually, I think this is a requirement of the HTTP protocol. (I'd be a little surprised if your browser didn’t get upset about it, too ...)Can you perhaps return 204 No Content? (See: this WikiPedia page...) Now, you are fulfilling the handshake obligation of the protocol, but saying that there is nothing else to say.
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