Cache persistence on domain name

Here is the current cache rule I am using in the 4.x:

 cache (not (http_host == "xxxx")) {  
    origin_pool Caches  
    cache_pool Caches  
  }

And we are going down to the 2nd level domain (i.e. yahoo.com)

Here is an iRule I came up with. Will it do the same?

 when HTTP_REQUEST {  
    if { [HTTP::host] != "xxxx"} {   
      pool cache_pool  
      persist universal [domain [HTTP::host] 2] 86400  
    } else {  
      pool cache_pool  
      persist universal [domain [HTTP::host] 2] 86400   
    }   
  }