[s.mmb] and [r.mmb] are sends and receives, respectively, that allow you to change their argument via an inlet. So you can easily re-route them. I originally made them to make it easy to give GOPs internal sends like the built-in GUI objects (like here). They're pretty self explanatory; check out the help files.

http://www.pdpatchrepo.info/hurleur/r.mmb.pd