It sounds like you want to have the browser listen for the server to talk. This usually involves writing your own server program, which isn't hard, but you need a dedicated server or something like that.

Here's some links, though:

• http://wp.netscape.com/assist/net_sites/pushpull.html : Netscape's idea of pushing data to a client.
• http://cgiirc.sourceforge.net/ : CGI:IRC, an IRC gateway writen in Perl.
• http://www.webmonkey.com/webmonkey/97/18/index2a.html : Old article on how to write a chat server in Perl. It's Telnet related, but it is easily adapted to HTTP pushing. I've done a smaller version of it.

If you feel like using something existing, but not Perl-based, there's a webchat interface to Jabber servers: http://jabberstudio.org/projects/jwchat/project/view.php