my %moves;
foreach my $i ( -7..-1, 1..7 ) {
  push @{$moves{'rook'}}, [$i,0], [0,$i];
}

my %valid_moves;
$valid_moves{'rook'} = [];
foreach my $i ( 0 .. 7 ) {
  $valid_moves{'rook'}->[$i] = [];
  foreach my $j ( 0 .. 7 ) {
    $valid_moves{'rook'}->[$i]->[$j] = [];
    foreach my $move ( @{$moves{'rook'}} ) {
      my $x = $i - ($move->[0]);
      next if ( $x < 0 or $x > 7 );
      my $y = $j - ($move->[1]);
      next if ( $y < 0 or $y > 7 );
      push @{$valid_moves{'rook'}->[$i]->[$j]}, [$x,$y];
    }
  }
}