$| = 1;

$seq = "";

sub other {
	for (my $w=0; $w<10; $w++) {
		my $s = substr($seq, -$w, +$w);
		foreach my $v (reverse 0..$w) {
			if (index($seq, $s . $v)<0) {
				$seq .= $v;
				return $v;
			}
		}
	}

	die "d'oh";
}

foreach my $n (1..10_000) {
	my $v = other();
	print "$n $v\n";
}