Something

Xchat::register("Test","0.1");
Xchat::hook_server("PRIVMSG",\&test_sub);

sub test_sub {
  if ($_[0][2] eq "#testing123" && $_[0][3] eq ":!3") {
    $chars = "UUDFBLR";
    $a = 0
    $b = 0
    for $i (1 .. 25) {      
      $rand = int(rand(6)) + 1;
      while ($rand == $a || $rand == $b && ((($rand == 1) && ($a = 2)) || (($rand == 2) && ($a = 1)) || (($rand == 3) && ($a = 4)) || (($rand == 4) && ($a = 3)) || (($rand == 5) && ($a = 6)) || (($rand == 6) && ($a = 5)))) {
        $rand = int(rand(6)) + 1; 
      }
      $b = $a;
      $a = $rand;
      $result = $result . substr($chars,$rand,1) . " ";
    }
    Xchat::command("msg #testing123 $result");
  }
  return Xchat::EAT_NONE;
}