Can iRule be used to modify HTML code itself being passed?

I was able to get regexes to work by wrapping the stream expression in {}'s:

This example looks for IP addresses in response content and replaces them with 0.0.0.0:

when HTTP_RESPONSE {
   STREAM::enable
   STREAM::expression {@\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}@0.0.0.0@}
}

Backreferences didn't seem to work though... the matched string is replaced with a literal \1.

Aaron