sub get_links {
	my @links;
	open(my $fh, "<", "links.alpha.sorted.25sample")
		or die "cannot open < links.alpha.sorted.25sample: $!";
	while(<$fh>) {
		chomp;
		my $tuple;
		@$tuple = split(/\s+/, $_);
		push(@links, $tuple);
	}
	return @links;
}