How to capture not eval'ed ERB


I need to capture a piece of erb by helper, modify it slighlty and
render it back. Really simplified version below:

def call_tag(tagname, *attrs, &block)
    content = capture(&block)
    concat render(:inline => process_content(content) :layout =>

However if content contains any escaped js, it will be escaped again
and left not working anymore. Is there ANY way to get ERB source and
to already compiled one (through capture helper) ?