Indeed, I was playing with Dyalog some months ago, and the most painful point was I/O. I have implemented the MAL (make a lisp) interpreter in APL but I cannot

Indeed, I was playing with Dyalog some months ago, and the most painful point was I/O. I have implemented the MAL (make a lisp) interpreter in APL but I cannot seem to make the tests for the self hosting interpreter run correctly because of the way standard error and standard output are treated :-/