multi-able ports and urls

Not tested but try this:

when HTTP_REQUEST {
    if {server_port < 84 || server_port > 84} {
        switch [HTTP::host] {
            "sf.stc.com" {
                HTTP::redirect "http://[HTTP::host]:85[HTTP::uri]"
            }
            "dd.stc.com" {
                HTTP::redirect "http://[HTTP::host]:86[HTTP::uri]"
            }
            "bo.stc.com" {
                HTTP::redirect "http://[HTTP::host]:87[HTTP::uri]"
            }
            "tt.stc.com" {
                HTTP::redirect "http://[HTTP::host]:88[HTTP::uri]"
            }
            "mm.stc.com" {
                HTTP::redirect "http://[HTTP::host]:89[HTTP::uri]"
            }
        }
    }
}