while ($keywords =~ /([-+]?)(?:'([^']*)'|"([^"]*)"|(\S+))/g) {
  my $cat = $1;
  my $keyword = $+;

  if ($keyword) {
    if ($cat eq '+') {
      push @KeysNeed, $keyword;
    } elsif ($cat eq '-') {
      push @KeysAvoid, $keyword;
    } else {
      push @Keys, $keyword;
    }
  }
}