my %found;
my %notfound;
@notfound{1..12} = ();
my $re = join "|", keys %notfound;
for my $key (keys %test) {
    if ($key =~ m/\.0?($re)\./) {
        my $month = $1 + 0;
        $found{$month} ||= 1;
        delete $notfound{$month};
        $re = join "|", keys %notfound;
        # wenn alle gefunden, braucht man gar nicht mehr suchen
        last unless keys %notfound;
    }
}
say for keys %found;