factory.p6

class Hexe::Stanza::Presence {
    method new($obj) {
        return self.bless(*);
    }   
}

class Hexe::Stanza::Message {
    method new($obj) {
        return self.bless(*);
    }   
}

class Hexe::Stanza {
    method create($obj) {
        given $obj<_tag> {
            when 'presence' {
                return Hexe::Stanza::Presence.new($obj);
            }   
            when 'message' {
                return Hexe::Stanza::Message.new($obj);
            }   
            default {
                return Failure("Unknown tag '$obj<_tag>'");
            }   
        }   
    }   
}

don't forget that bless with a whatever star argument is now deprecated