This post will be extremely valuable to about 3 people in the world.
I finally found a simple solution for programming with a Scheme REPL in Vim. However, this is useful for REPLs, LISPs, and any “UNIX-interactive” program.
install exec_with_piped somewhere. (For further reading see mod_pipe)
in a terminal, run this:
./exec_with_piped /path/to/YOURPIPE “YOURREPL”
i.e. ./exec_with_piped [...]