Note that the 12,701 character regex is WRONG. It doesn't even match "70". Even the binary regex is wrong.

The original 32K regex pointed to in the stackexchange problem statement however is perfectly correct.

Test code:

    open(F, '< /tmp/q.in');
    $myre = <F>;
    chomp($myre);
    $myrecomp = qr/^(?:$myre)$/;
    while (<>) {
      chomp();
      if (m/$myrecomp/) {
        print "$_\n";
      }
    }

Examples of multiples of 7 not matched by the given regex: 70, 707, 7007, 11095

(I spent all morning trying to find the bug in my regex compiler based on the assumption that the answer there was correct)