use Data::UUID; use Class::BuildMethods 'name', rank => { default => 'private' }, age => { validate => sub { my ($self, $age) = @_; die "Must be 18 or over" unless $age >= 18; }, }, id => { default => Data::UUID->new->get_str, validate => sub { die "id() is readonly" } }; sub new { bless [], shift } sub foo { my $self = shift; return $self->[0] unless @_; # lots of horribly complicated code $self->[0] = shift; return $self; }