I recommend an APL offspring to someone who wants to expand their horizons, rather than APL itself: K (or a variant thereof), or J. No special chars needed. J

I recommend an APL offspring to someone who wants to expand their horizons, rather than APL itself: K (or a variant thereof), or J. No special chars needed. J used to be the only freely available, and with better documentation -- however, it is also a larger language. It seems that recently the K dialects (oK, klong, kuc, kerf, xxl) are plentiful, freely available and well documented. It is also my experience that K is less frightening to most people - J uses e.g. curly braces independently as operators, which looks a-priori broken to most people (rather than just unintelligible like K does).