Keep stack between eval #5500

I am implementing a REPL and want to keep local variables between calls to eval. I've looked at mirb and tried to do what it does, but I get a crash, maybe because I'm initiating the call from ruby instead of C, so I guess I call vm exec recursively ?

I also looked at eval.c but it's more complex (maybe because it needs to work when called from ruby).

Any help appreciated.