It looks like you are making some interesting and perhaps false assumtions. You are assuming that the '9' digit is a valid pin number and that multiple iterations of randomly generated numbers will produce at least one of every digit. A better test would be:

my $pin;
1 while ( $pin = pin() ) =~ /\A\d{4}\z/;

my $digits = "\0" x 10;
do {
    substr $digits, $_, 1, $_ for pin() =~ /\d/g;
    } until $digits =~ /\A\d{10}\z/;
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And of course the first test will never end unless a stray gamma ray hits your CPU and changes the constant 4 to some other number.   :-)