my @displacement = (
    [-1, -1],
    [-1,  0],
    [-1, +1],
    [ 0, -1],
    [ 0,  0],
    [ 0, +1],
    [+1, -1],
    [+1,  0],
    [+1, +1],
    [-1, -1],
);

sub check_coord {
    my ($x, $y, $wall, $coord)= @_;

    for($displacement[$coord - 1]) {
        $x += $_->[0];
        $y += $_->[1];
    }

    return
        if $y < 0 or $x < 0
        or not defined(
           $map[$y]
           or $map[$y][$x]
        );

    return $map[$y][$x] eq $wall;
}