On Tue, Mar 18, 2014 at 9:00 PM, Richard Stallman <rms@gnu.org> wrote:

>     A quick peek+edit in a #include in C, or "use My::Module" in Perl
> (where
>     you can say `perldoc -l My::Module' to find the module file), etc.
> would
>     be handy.
>
> We already have such features, but they display the other file in
> another buffer.   Why is it useful to put them in one buffer?
>
> What does it look like, to have multiple files in one buffer?


One possibility, which may not be optimal but which does have
the distinct advantage of already being implemented, is Magnar
Sveen's multifiles.el[0] library, inspired by this[1] question.

Incidentally, I've often wished for the inverse functionality,
i.e. the ability to conveniently partition a file-visiting buffer into a
set of indirect buffers, which could then have different major
modes, buffer-local variable values, minor modes, etc.  Maybe
someone will tell me that this, too, already exists :)

[0] https://github.com/magnars/multifiles.el
[1]
http://www.reddit.com/r/emacs/comments/10gc9u/can_i_have_multiple_parts_of_buffers_in_one_super/

Josh