Thanks for your quick response, I tried your code and am getting the same false positives.

Example: $prompt_host = "BR|GR", filenames such as: YUGRABCKFI01-1.1.1.1_2011.10.04.00.00.00.txt and GRREPCCOBE10-1.1.1.1_2011.10.04.00.00.00.txt are erroneously being pushed. Here is how I implemented your code:

 while (my $file = readdir(DIR)) {
    if($file =~ m{ \A [A-Z0-9]{8} $prompt_host }xms) {     
        push(@traffic_file_list, $file);
    }
}
[download]