If/else in index.rss.builder

Hi. I'm new to Rails. It's my first post here.

So I have an index.rss.builder (http://gist.github.com/602773)
On line 10 I want to check for an excerpt before showing:

post.excerpt + '<p>***</p>' +

I know how to do if/else in views, but not here.

Thanks

it's ever simpler than a view because a .builder file is pure ruby - a
normal if/else is all you need.

Fred