my $response = $browser->post($url,
          [ 'Encounter1847760942' => "$enc_id",
            'SelectType1847760942' => "StartOnSelect",
            'Begin1847760942' => "01/02/2005",
            'DaysBack1847760942' => "3",
            'ProcedureSearchText1847760942' => "",
            'EncounterOptionSelected' => "false" ], @ns_headers);

##</code><code>##

$response = $browser->content($poststring);
# where $poststring = 'checkbox'=>\"1\"" etc....