$M = 8;
    $A = 5;
    $X = 0;
    $C = 0;
    
    sub lcrng {
        $X = (($X * $A) + 1) % $M;
        
        $C++;
        if ($C = $M-1) {
            $C = 0;
            $X = lcrng();
        }
        return ($X);
    }