my ($previous,$next);
my @keys = sort { $a <=> $b } keys %hash;

for (my $i=0; $i < scalar @keys; $i+=1) {
	$previous = $keys[$i-1] unless $i == 0;
	$next     = $keys[$i+1] unless $i == scalar @keys;
	last if $keys[$i] == $current;
}