The *other* lisp interaction mode

[Perry Smith]

Within the past few months, someone mentioned a mode they use to tinker with 
emacs lisp.  As I recall, it had a prompt like '==> ' but I'm not 100% of that. 
 What I do recall is when I evaluated a long list like auto-mode-alist, it 
would give me the whole list rather than only part of it with the dot dot dots.

I've searched the list archive and googled the past hour and can't find what 
I'm talking about.  Can someone refresh my memory?

Thanks
pedz