sub rs{
    my @chars = map chr, 33..126;  # all printable chars
    if (defined $p) {
        # don't use anything allready in our pattern
        @chars = grep  index($p,$_)==-1,  @chars;
    }
    my $r;
    $r .= $chars[rand @chars] for 1 .. shift;
    $r or '';
}