Try changing your Javascript so that it sets the MIME type of the request: 
http_request.open('POST', "/index.pl/get_neigh_display", true);
http_request.setRequestHeader('Content-Type', 'application/x-www-form-
+urlencoded');
http_request.send(query);

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In reply to Re: Firefox/Javascript/Perl CGI argument passing issue by tangent
in thread Firefox/Javascript/Perl CGI argument passing issue by beckmanel

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