sub display {
	my $curr = shift;
	while (1) {
		last unless defined $curr->{next};
		print "Current: ", $curr->{data}, 
		      "\tPrevious: ", $curr->{prev}{data} // "", 
		      "\tNext: ", $curr->{next}{data} // "", "\n";
		$curr = $curr->{next};
	}
    print "\n";
}