if ( defined $rulelist->{$rulenum}->{REGION} ){
      my $rule = $rulelist->{$rulenum}->{REGION};
      if ( $rule =~ s/!// ){ # handles negation
         if ( $line -> {REGIONID} == $rule ){ next RULE };
      }
      elsif ( $line -> {REGIONID} != $rule)  { next RULE };
      ...