package Foo;
use strict;
use Data::Dumper;

sub list_params {
  my ( $self, cgi ) = @_;
  my %formdata;

  defined($cgi) && ref($cgi) && $cgi->isa('CGI')
    or return 0;

  foreach my $key ( $cgi->param ) {
      $formdata{ $key } = _format_vals( [ $cgi->param( $key ) ] );
  }
      
  Dumper( \%formdata );
}