sub clean
{
    my ($dir) = @_;
    opendir (DIR, $dir) or {warn "cannot opendir $dir" and return};
    my (@subdirs, @files);
    map {
        push @subdirs, $_ if (-d "$dir/$_" && $_ !~ /\.|\.\./);
        push @files, $_ if (-f "$dir/$_");
    } readdir(DIR);
    closedir(DIR);
    map {&clean("$dir/$_")} @subdirs;
    print "DIR - $dir\n";
    foreach my $file (@files) {
        # do thing on each file
    }    
}