I have strange situation. I need to call a program in cgi-bin from within a perl script. When I try to do that with exec($program), I get

(20014)Internal error: proxy: error reading status line from remote server
proxy: Error reading from remote server returned by ...

The long story... I am calling mapserv (http://mapserver.org) as a cgi program from OpenLayers (http://openlayers.org). Ordinarily, my web site is served by Perl Dancer, but the mapserver calls are made directly to http://server/cgi-bin/mapserv from JavaScript. The Dancer web site is served by Starman behind an Apache2 proxy front-end. This is how it looks

[browser] -> http://server/app -> [apache2] -> proxy port 5000 -> Starman
    |
    |
    +-> http://server/cgi-bin/mapserv -> [apache2] -> cgi-bin -> mapserv

This is what I am trying to accomplish

[browser] -> http://server/app -> [apache2] -> proxy port 5000 -> Starman
                                                                    |
                                                                    |
                               mapserv <-- cgi-bin <-- [apache2] <--+

I saw this question re: 20014 error, but that suggested solution didn't help.

Any other hints?