sub show_excel {
  my $self = shift;
  my $file = "temp.xls";
  my $output = do {
    local $/; open FH, 'temp.xls' or die "$!"; <FH>
  };
  $self->header_props(-type => application/vnd.ms-excel',
                      -attachment => $file);
  return $output;
}