Take a look at
CGI::SSI again. In the previous discussion,
dws mentions using
<!--#exec cmd=""-->.. which is correct based on the CGI::SSI documentation.
<!--#exec cgi="..."--> is no longer being supported. But
<!--#exec cmd="..." --> is supported,
but "the package variable CGI::SSI::allow_exec has to be set to true (and will fail in any case if your CGI is running in taint mode, as it should be!)."