sub validate_data($$)
{
    my $q = shift;
    my $tmpl = shift;

    my %data = ();
    my %invalid = ();

    foreach my $key (keys %{$tmpl})
    {
        my $value = $q->param($key);
        if (&{$tmpl->{$key}}($value))
        {
            $data{$key} = $value if defined $value;
        } else {
            $invalid{$key} = 1;
        }
    }

    return (\%data, \%invalid);
}