In a manner of speaking. Some things are difficult to do in HAML, which happen to be things you shouldn't be doing anyway.

For example, I don't know how to write multi-line Ruby code (with the exception of function calls) in HAML. I wouldn't be surprised if there is a way, but you can't just drop it in like you can with ERB. This means that if you need multiple lines of Ruby, you move the code a more appropriate area (model, helper, controller, etc).