class Staff::Record {
    has Str  $.name;
    has Int  $.rank;
    has Hash $.pref;

    method CREATE(Str $name, Int $rank, Hash $cereal_pref) {
      .check_rank($rank);
      ($.name, $.rank, $.pref) = ($name, $rank, $cereal_pref);
    }

    method name() returns Str {
      return $.name;
    }

    method rank() returns Str {
      return $.rank;
    }

    method rank(Int $new_rank) {
      .check_rank($new_rank);
      $.rank = $new_rank;
    }

    method check_rank(Staff::Record $obj: Int $rank) is private {
     die "Invalid rank for $obj.class() object: $rank"

       unless 0 < $rank < 10;
    }

    # Other methods here
}