sub valid_record {
        my %field = @_ ;
        my $valid = 1 ;
        my $why   = '' ;
        # Do some multi-field validation, e.g.
        if( $field{'colour'} eq 'blue' and
            $field{'make'} eq 'estate' ) {
          $valid = 0 ; # No blue estates available.
          $why   = '<b><i>No blue estates available</i></b>' ;
        }
        # etc.
        ( $valid, $why ) ; 
    }