The example in the manual that invokes the cli version of 
php works. But If I try to do the same thing with R (the 
statistics package at www.r-project.org) it hangs. Almost 
the same problem with bc -- output is only seen there if 
the fwrite connection is closed before doing an fread/fget.
R buffers its output in non-terminal mode so I have tried 
modifying the source of R to force line-buffered output -- 
no joy. I have also tried calling R indirectly via the 
unbuffer script that comes with expect -- no joy. I have 
also tried the pty example program from "Advanced 
Programming in the Unix environment -- no joy.