deref ($_[0]->{$1}, $_[1]);

##</code><code>##

sub deref {
 return \$_[0] unless $_[1] =~ s/^-([\w\._]+)//;
 $_[0]->{$1} ||= {}; # Vivify an anonymous hash if needed.
 deref ($_[0]->{$1}, $_[1]);
}