while (<FILE>) {
  # no need for chomp, because you strip whitespace below
  if (my($quote, $person) = /(.*?)--(.*?)/s) {
    s/^\s+//, s/\s+$/ for $quote, $person;
    print "$quote\t$person\n";
  } else {
    # no --, so just show the cleaned up quote:
    s/^\s+//, s/\s+$/;
    print "$_\t(Unknown)\n";
  }
}