use Class::CGI
    handlers => {
      invoice_date => 'My::Date::Handler',
      sales_date   => 'My::Date::Handler',
    };
  my $cgi  = Class::CGI->new;
  my $date = $cgi->param('invoice_date');
  my $date = $cgi->param('sales_date');
  my $day  = $date->day;