I agree also that io is a good place for the basic version that doesn't do file descriptor stuff and maybe the fancy file descriptor stuff should be a separate issue and should go in subprocess.

To move this along and generate more discussion, I took code from Nick earlier in the thread and made a little patch and a test program and put it in a gist:

https://gist.github.com/msabramo/6049140

If folks like that, I can convert the test program into an automated test. 

What do you guys think?