Testing attribute existence on 3.x

[Phil Mayers]

I have a feeling I've asked this before so apologies if so, but...

How do I do this:

  if (list:Attr) {
  }

I just get:

       ^ Expected a module return code

...on startup when I do this. This seems gross:

  if (list:Attr =~ /.*/) {
  }

...but does work.

This is with current GIT head. "man unlang" seems to suggest what I'm 
doing should work?