irule-based redirection & maintenance page

when HTTP_REQUEST {  
     make sure $dn is an actual pool  
    set dn "empty_pool"  
    
     choose a vhost based on requested site name  
    switch [string tolower [HTTP::host]] {  
      www.sitename1.com { set up www.sitename.com; set dn www.sitename.com_down }  
      www.sitename2.com { set up www.sitename.com_80 }  
      www.complexsite.com { set up www.complexsite.com }  
    }  
    
     check for sites that need special treatment first, then sites that are up  
     then down sites (with a down pool), then down sites (with no down pool)  
    if { $up equals "www.complexsite.com" and [active_members $up] > 0 } {  
      switch -glob [string tolower [HTTP::uri]] {  
        "/uri1*" - "/uri2*" - "/uri3/pagename.html" { use pool $up }  
        default { HTTP::uri "/append/to/beginning[HTTP::uri]"; use pool $up }  
      }  
    }  
    elseif { [active_members $up] > 0 } { use pool $up }  
    elseif { [active_members $dn] > 0 } { use pool $dn }  
    else {  
      switch -glob [string tolower [HTTP::uri]] {  
        "/" { HTTP::respond 200 content [b64decode [class element -value 0 maint_fxcm]] "Content-Type" "text/html" }  
        "/logo.gif" { HTTP::respond 200 content [b64decode [class element -value 1 maint_fxcm]] "Content-Type" "image/gif" }  
        "/top-backbanner.jpg" { HTTP::respond 200 content [b64decode [class element -value 2 maint_fxcm]] "Content-Type" "image/jpeg" }  
        default { HTTP::redirect "/" }  
      }  
    }   
  }