iRule needs updating from HTTP_CLASS for 11.4.x

All, I was hoping someone could help me with the ASM iRule. I need the HTTP_CLASS removed as that option cannot be used on 11.4.x. I would appreciate any help in the right direction.

ltm rule block_webbots2 {
    when HTTP_REQUEST {
   set abort_trans 0
    Check the UA header value, set to lower case
   switch -glob [string tolower [HTTP::header User-Agent]] {
      "_googlebot_" -
      "_msnbot" -
      "_yahoo" {
          Bad UA, send a TCP reset
         set abort_trans 1
      }
   }
}
when HTTP_CLASS_SELECTED {
   if {[HTTP::class asm]==1}{
      if {$abort_trans==1}{
         ASM::disable
         reject
      }
   }

else
   {
      if {$abort_trans==1}{
         reject
      }
   }
}
}