RPC-Exec allows implementing pligin as a separated executable in its own language, connected with the main program via json-rpc-1.0 as described in http://json-rpc.org/wiki/specification. It was started during development of some perl code, for prototyping new functionality in Haskell. I did not feel like messing with FFI of both them in a single process, so decided to go this way.
Later it turned out to be not needed, but I still have some plans to use it, so let it be around, just in case.
The tree contains haskell library RPC. It is a primary implementation. It supports running a program or custom connection from two handles. It can handle requests in both ways, and intended to be able to run several requests in parallel, though this is not yet so. It is still a deep alpha, particularly some very important things still not implemented.
Also contains a perl library RPCX.pm. It is not working, only sketched. I intended it to be able to act as a simple client.