<?^open Unix ?>  <?let st = stat "robots.txt" in 
    let sz = float_of_int st.st_size in
    let (amt, unit) = match arg "unit" with
          | Some "M" -> (sz /. 1048576., "M")
          | Some "k" -> (sz /. 1024., "k")
          | _          -> (sz, "") ?>
<?"%.1f%s" amt, unit ?>