Consider the following expect script:

#!/usr/bin/expect

spawn bash
interact {
  -o
  hello_world { send "Goodbye" }
}

Under this script, any time the process sends hello_world, the hello_world disappears and turns into Goodbye.
I could explicitly write send_user("hello_world") to bring it back, but I am wondering if there is an option such as -echo for user input that would tell expect to show the process output anyways.