my %data = {
   'Cities'=>{
      'CityA'=>{
         'PopByAge/Gender'=>{
            'Ages 0-9'=>{'Male' = 220,'Female' = 180},
            ...
      },...
    },
    'Tables'=>{
       'PopByAge/Gender'=>{
          'Ages 0-9'=>{
             'CityA'=>{'Make'=>220, 'Female'=>180},
             ...
    ...
};