my $first;
my $prev_node;
for (1..5) {
	my $node = { value => $_, prev => $prev_node };
	$first //= $node;
	$prev_node->{next} = $node;
	$prev_node = $node;
}

my $node = $first;
while ($node) {
	say $node->{value};
	$node = $node->{next};
}