URL host rewrite based on URI

 
 when HTTP_REQUEST { 
  
     Check if the subdomain starts with www. or is null 
    if {[string tolower [HTTP::host]] starts_with "www." or [HTTP::host] eq ""}{ 
  
        Exit this event in this rule 
       return 
    } 
    log local0. "Host didn't start with www: [HTTP::host]" 
  
     Save the first directory in the HTTP path, set to lower case 
    set first_dir [string tolower [getfield [HTTP::path] "/" 2]] 
  
     Check if the first directory matches some pattern like "product" 
    if {not ($first_dir starts_with "product")}{ 
  
        Exit this event in this rule 
       return 
    } 
    log local0. "\$first_dir, $first_dir, matched the pattern check" 
  
     Check if the first directory in the path is not the same as the subdomain 
    if {$first_dir ne [getfield [string tolower [HTTP::host]] "." 1]}{ 
  
          log local0. "Redirecting request to $first_dir.xyz.com" 
          HTTP::redirect "$first_dir.xyz.com" 
       } 
    } 
 }