my @dist;
&flood($cheese{x},$cheese{y},0);
die "No route to cheese!" unless defined $dist[$mouse{x}][$mouse{y}];

sub flood {
  my ($x,$y,$dist) = @_;
  return if defined $dist[$x][$y] and $dist[$x][$y] < $dist;
  $dist[$x][$y] = $dist++;
  flood($x-1,$y,$dist) unless $map[$x-1][$y];
  flood($x+1,$y,$dist) unless $map[$x+1][$y];
  flood($x,$y-1,$dist) unless $map[$x][$y-1];
  flood($x,$y+1,$dist) unless $map[$x][$y+1];
}