croak "no wheels specified" unless @_;
-	my @w = map { [ 1, ref eq 'ARRAY' ? @$_ : $_ ] } @_;
+	my @w = map { [ 1, ref eq 'CODE' ? $_->() : $_ ] } @_;
 	my $done;

##</code><code>##

sub odometer {
	die "no wheels specified" unless @_;
	my @w = map { [ $_, $_->() ] } @_;
	my $done;
	return sub {
		if ($done) { $done=0; return }
		my @cur = map { $_->[1] } @w;
		for ( my $i=$#w; $i>=0; $i-- ) {
			defined( $w[$i][1] = $w[$i][0]->() ) and last;
			$w[$i][1] = $w[$i][0]->();
			$done=1 unless $i;
		}
		return wantarray ? @cur : join '', map {defined()?$_:''} @cur;
	};
}

##</code><code>##

use Test::More;
sub array_it {
	my ($i,@arr) = (0,@_);
	return sub { if ( $i>$#arr ) { $i=0; return } $arr[$i++] }
}
{
	my $odo = odometer( array_it('foo','bar'), array_it('-'),
		array_it(3..5) );
	my @o;
	while (defined( my $x = $odo->() )) { push @o, $x }
	while (my @x = $odo->()) { push @o, \@x }
	is_deeply \@o, ["foo-3", "foo-4", "foo-5", "bar-3", "bar-4",
		"bar-5", ["foo","-","3"], ["foo","-","4"], ["foo","-","5"],
		["bar","-","3"], ["bar","-","4"], ["bar","-","5"] ];
}
{
	my $odo = odometer(
		array_it(qw/ a b c /),
		array_it(qw/ 1 2 /,undef,qw/ 3 4 /),
	);
	my @o;
	while (defined( my $x = $odo->() )) { push @o, $x }
	is_deeply \@o, [qw/ a1 a2 b3 b4 c1 c2 /];
	@o = ();
	while (defined( my $x = $odo->() )) { push @o, $x }
	is_deeply \@o, [qw/ a3 a4 b1 b2 c3 c4 /];
}
done_testing;