Getting a forwarding port from a URI

Can I assume that if there's nothing after the port number then the newuri variable is empty? If so, then a quick check and replace function should do the trick:

if { not ( $newuri starts_with "/" ) } { set newuri "/${newuri}" }

So it might look something like this:

when HTTP_REQUEST { 
    set newuri [findstr [HTTP::uri] "/" 5]
    if { not ( $newuri starts_with "/" ) } { set newuri "/${newuri}" }
    log local0. "Original request is: [HTTP::host][HTTP::uri]" 
    log local0. "New URI is: $newuri" 
    set newport [findstr [HTTP::uri] "/" 1 4] 
    HTTP::uri "$newuri" 
    log local0. "New Port is: $newport" 
    HTTP::header replace Host "[HTTP::host]:$newport"

    if { $newport ne "" } {
        Use the relevant Pool
        pool mule_pool_$newport
    } else { 
        log local0. "Newport Variable was empty"
    }
}