sub recurse_tree {
    my ($root) = @_;
    $root =~ s!/$!!;
    my @dirs = ( $root );
    for my $dir ( @dirs ) {
        opendir DIR,  $dir or do { warn "Can't read $dir\n"; next };
        for my $file ( readdir DIR ) {
            # skip . dirs
            next if $file eq '.' or $file eq '..';
            # skip symlinks
            next if -l "$dir/$file";
            if ( -d "$dir/$file" ) {
                push @dirs, "$dir/$file";
            }
            else {
                push @files, "$dir/$file";
            }
        }
        closedir DIR;
    }
  return \@dirs, \@files;
}