builder_with_funargs.erl

Xml:posts do 
    lists:each(Posts) do |Post| 
        Xml:post do 
            Xml:title(Post#post.title), 
            Xml:body(Post#post.body), 
            Xml:published_at(Post#post.published_at), 
            Xml:comments do 
                lists:each(Post#post.comments) do |Comment| 
                    Xml.comment do 
                        Xml:body(Comment#comment.body) 
                    end 
                end 
            end 
        end 
    end 
end

normal_erlang_builder.erl

Xml:posts(fun() -> 
    lists:each(fun(Post) -> 
        Xml:post(fun() -> 
            Xml:title(Post#post.title), 
            Xml:body(Post#post.body), 
            Xml:published_at(Post#post.published_at), 
            Xml:comments(fun() ->
                lists:each(fun(Comment) ->
                    Xml.comment(fun() -> 
                        Xml:body(Comment#comment.body) 
                    end)
                end, Post#post.comments)
            end)
        end)
    end, Posts)
end)