sub zip {
  my($l1, $l2) = @_;
  die "zip(): expects two ARRAY refs\n"
    if ref($l1) ne 'ARRAY' or ref($l2) ne 'ARRAY';
  my %ret; @ret{ @$l1 } = @$l2;
  return map { $_ => $ret{$_} } @$l1;
}