how to use data group

 
   when HTTP_REQUEST {  
    
     log local0. "[IP::client_addr]:[TCP::client_port]: [HTTP::method] request to [HTTP::host][HTTP::uri]"  
    
     find a match using host+uri against the class and  
     returns the whole string (field1 field2 field3)then  
     set it as newURI variable.  
 set newURI "[findclass [HTTP::host][HTTP::uri] $::redlist]"  
     if { $newURI ne "" } {  
    
        log local0. "[IP::client_addr]:[TCP::client_port]: Matched line $newURI"  
    
         Parse the three fields in the matched datagroup line  
        scan $newURI {%s %s %s} unused host uri  
    
        log local0. "Parsed: $unused $host $uri"  
    
        change host and uri  
        if {$host ne ""}{  
   log local0. "Setting new host to $host"    
   HTTP::header replace Host $host 
        }  
        if {$uri ne ""}{  
   log local0. "Setting new uri to $uri"    
           HTTP::uri $uri  
        }  
     }  
  }