Can Emacs pipe a buffer through another one?

[J Krugman]

Suppose I have two buffers A and B, not necessarily associated with
a file on disk, and furthermore, suppose that B's content is a
script (bash, perl, python, etc.) that prints to STDOUT a transform
of whatever it reads from STDIN.  (Assume that the first line of
B is a suitable shebang line.)  It would be really cool if, without
leaving Emacs, and without creating any new files on disk, one
could feed the contents of buffer A as STDIN to the script in buffer
B, and take the resulting output and insert them in some other
buffer C (possibly replacing some or all of C's contents).  (Of
course, there should be no reason why these buffers should all be
different from each other.  For instance, B could be a script that
rewrites itself.)

Even cooler would be if instead of using whole buffers for program
and data as described above, one could use regions.

Can one already do any of this in Emacs?  If not, can someone give
me a clue about how to write such a thing in Emacs Lisp?

Thanks!

jill

-- 
To  s&e^n]d  me  m~a}i]l  r%e*m?o\v[e  bit from my a|d)d:r{e:s]s.