foreach (readdir(DIR)) {
    if (/^([a-z0-9]*?-[a-z]{2}-[a-z]{2,3})-(\d{8})(-eol)?\.(pdf|html)$/) {
      push(@{$files{$1}}, $2);
    }
  }

##</code><code>##

  foreach (keys %files) {
    $files{$_} = [sort @{$files{$_}}];
  }