You need to start "some program" and make two pipes: one feeding to its standard input, and one reading from its standard output. I think there is even a pipe3 version, but don't recall if that's the right thing.
in reply to Re^2: Bidirectional IPC with Expect and Passthrough
in thread Bidirectional IPC with Expect and Passthrough
Without the fancy syntax, you can create a named pipe, and then as a separate step use the redirection syntax ">" to send the output of the program to the pipe you previously opened. You have the other end and can read from that. You can use the pipe syntax for the other direction (only) or use "<" and ">" in the `system` construct to do them both with named pipes.