This function constitutes the 'main program' of the metacircular evaluator. The way it functions is very simple. First, the globals are installed in the global environment. Then a read-eval-print-loop (REPL) is started which runs until the metacircular pico programmer enters an empty Pico program. Entering an empty Pico program (on most systems, this happens by pressing enter) is the convention to stop the metacircular evaluator.