Redirect based on URI content

Issue 1:

This will redirect the client:

 
 if { [domain [HTTP::host] 2] equals [HTTP::host] } { 
   HTTP::redirect www.[HTTP::host] 
 } 
 

This will just fix the header, with no change in client's perspective:

 
 if { [domain [HTTP::host] 2] equals [HTTP::host] } { 
   HTTP::header replace Host "www.[HTTP::host]" 
 } 
 

Issue 2:

Is this also for the same rule as Issue 1? If so, in which order should they be evaluated? it can't be sent to both www and sub.