I think you want

$file_re =
  qr/(?:(nonconsolidated|other)$underscore)?
     (faq|organization|literature|contact|service)
     $underscore($non_dot+)
     ${dot}xls/ix;
[download]

to (1) not capture the first brackets and (2) to get case insensitivity (should be regexp compile time and (3) that's where the x to ignore whitespace should be as well.

Hope this helps, -gjb-

Update: added formatting and x option to qr.