Can Emacs save a file to more than one place at the same time?

[Marcin Borkowski]

Hi all,

I'd like to have more than one copy of the exact same file.  It would be
best if I could just edit a buffer and hit `C-x C-s` to get its contents
saved to more than one file.  I'm almost sure there is no such thing in
core Emacs, and I think coding this myself would be pretty easy (the
most difficult part would be obviously the UI).  But maybe someone
already did it and there's a package for that?

TIA,

-- 
Marcin Borkowski
http://mbork.pl