RE: What is the :eval form ?

[Drew Adams]

> I'm trying to get some information about this (e?)lisp form
>   (add-to-list 'global-mode-string
>              '(:eval (mail-bug-mode-line-all "2")))
> 
> How can I find information about this special form ?
> When I ask emacs using C-h f with point over it

:eval is not a function here.

What you want to do is ask Emacs about variable `global-mode-string': `C-h v
global-mode-string'.

That help buffer includes a link to help on variable `mode-line-format'.  If you
click that link you will find information about :eval.