I changed the definition of the show and toggle methods like this:

sub show {
    my $board = shift;
    print "\e[H";
    for my $row (@$board) {
        return unless defined $row;
        print map $_ ? '*' : defined $_ ? '.' : '', @$row;
        print "\e[K\n";
    }
    print "\e[J";
    use Time::HiRes "sleep";
    sleep(6e-3);
} # show

sub toggle {
    my ($board, $x, $y) = @_;
    my $old = $board->[$y][$x];
    return unless defined $old;
    $board->[$y][$x] = $old eq 1 ? 0 : 1;
} # toggle
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