#! perl
use strict;
use warnings;

while (<DATA>) {
  print if /(\d)(?=.*\1)/g and not /($1)(?=.*\1)/g;
}

__DATA__
0000 (Don't pick)
0001 (Don't pick)
0012 (Pick)
0011 (Pick)
1001 (Pick)
1009 (Pick)
1234 (Don't pick)
9879 (Pick)