vhost equivalent

I'd like to run an http server that serves pages for multiple domains
using the same server IP.  I thought it would be sufficient to create
two instances and two associated instance configurations.

configuration "firstdomain":
        hostname firstdomain.com
        enable head
        enable get
        pass /* /firstdomain.com/*

configuration "seconddomain":
        hostname seconddomain.com
        enable head
        enable get
        pass /* /seconddomain.com/*

This way, I was thinking, browser requests for firstdomain.com and
seconddomain.com would be handled by the appropriate instance and the
proper index.htmls would be served.  They aren't.  If this configuration
is crazy, please tell me why.

For added wacky fun, the pages are being served in EBCDIC. Must ASCII
web pages be located in one of the subfilesystems of the IFS?  I seem to
remember something about QDLS but can't recall.

Thanks.

brian.