sub _url_encode_data 
{   
    my ( $data ) = @_;   
    
    my $post_string;
    
    foreach my $field ( keys %$data ) 
    {
        next if ( $data->{$field} eq '' );
    
        $data->{$field} =~ s/([^a-zA-Z0-9_\-.])/uc sprintf("%%%02x",ord($1))/eg;
    
        $post_string .= "$field=$data->{$field}&";
    }
    
    return $post_string;
    
} # END _url_encode_data