use IO::Dir;
sub make_reader2 {
    my ($dirname) = @_;
    my $d = new IO::Dir $dirname or die "opendir $dirname: $!";
    my $next;

    return sub {
        while (1) {
            unless (defined $next) {
                my $entry = $d->read or return;
                next if $entry eq '.';
                next if $entry eq '..';
                $entry = "$dirname/$entry";
                if (-d $entry) {
                    $next = make_reader2($entry);
                } else {
                    $next = sub { my $r = $entry; undef $entry; $r; };
                }
            }

            my $result = $next->();
            return $result if defined $result;
            undef $next;
        }
    };
}

my $reader = make_reader2($ARGV[0]);
print "$_\n" while (defined($_ = $reader->()));