my $months = (
      '1'     => 'January',
      '2'     => 'February',
      '3'     => 'March',
      '4'     => 'April',
      '5'     => 'May',
      '6'     => 'June',
      '7'     => 'July',
      '8'     => 'August',
      '9'     => 'September',
      '10'    => 'October',
      '11'    => 'November',
      '12'    => 'December',
);

print $query->popup_menu({ -name => 'month', -values => [ sort { $a <=> $b } keys %{$months} ], -labels => $months });

-------------------------------------------

Can't use string ("December") as a HASH ref while "strict refs" in use