%squares = (
        a1 => $a1,
        a2 => $a2,
        a3 => $a3,
        b1 => $b1,
        b2 => $b2,
        b3 => $b3,
        c1 => $c1,
        c2 => $c2,
        c3 => $c3
);

##</code><code>##

# makes the moved piece blank
sub make_blank() {
    $squares{$response} = " ";
}