Streaming - Logging when content exists

That's what I'm talking about... I don't know if you've checked the wiki, but it seems to be extremely lacking when it comes to information and examples about the STREAM commands.

I got something working for what I wanted.

when HTTP_REQUEST {
  set uri [HTTP::uri]
}
when HTTP_RESPONSE {
  STREAM::enable
  STREAM::expression {@http://@}
}
when STREAM_MATCHED {
  log "URI $uri contains http reference"
}

What I'm trying to do now is find a way to extract not just the exact text matched but enough text afterwards that I might be able to see in the log what link contained the http reference. Is there some way that I might capture the subsequent characters until a certain character is matched (space, quotation mark, whatever), or even grab a set number of characters after (say, the next 30 characters)? I hope that makes sense.