+}
+
+sub require_subdir ($) {
+ # => list of descendant subdirs
+ my ($here) = (@_);
+ my $prefix = $here eq '.' ? qr{} : qr{$prefix/};
+ my @children = grep { m{^$prefix[^/]+$} } @allsubdirs;
+ my @descendants;
+ foreach my $child (@children) {
+ push @descendants, require_subdir(