sub put_element {
  my ($hashref, @path) = @_;

  # The leaf node and its value are special
  my $value = pop @path;
  my $leaf = pop @path;

  # walk the tree, create non-existing nodes
  for my $node (@path) {
    $hashref = $hashref->{$node} ||= {};
  }

  # Finally, set the value at the leaf
  $hashref->{$leaf} = $value;
}