Re: header-line-format hacking

[ytrewq1]

David Hansen writes:
 
> Just set `header-line-format', e.g:
> 
> (setq header-line-format (concat (or header-line-format "") " test"))
> 
> will append " test" to the header line of the current buffer.

I was under the impression that the header-line-format variable
can hold a template like the one that mode-line-format uses.  If
that's the case, wouldn't the code snippet above not work for
non-string templates?