hpricot：Hpricot::Elements#after

everyday Ruby 
>> require "hpricot"
=> true
>> doc = Hpricot('<p>foo1</p><p>foo2</p>')
=> #<Hpricot::Doc {elem <p> "foo1" </p>} {elem <p> "foo2" </p>}>
>> (doc / "p").after("foo")
=> #<Hpricot::Elements[{elem <p> "foo1" </p>}, {elem <p> "foo2" </p>}]>
>> doc.to_html
=> "<p>foo1</p>foo<p>foo2</p>foo"
>> doc = Hpricot('<p>foo1</p><p>foo2</p>hoge')
=> #<Hpricot::Doc {elem <p> "foo1" </p>} {elem <p> "foo2" </p>} "hoge">
>> (doc / "p").after("foo")
=> #<Hpricot::Elements[{elem <p> "foo1" </p>}, {elem <p> "foo2" </p>}]>
>> doc.to_html
=> "<p>foo1</p>foo<p>foo2</p>foohoge"

ブロックに何を渡せるのか不明