I can't suppress MAPM warnings (and I'd like to).
That particular message ("Warning") only comes from one place.
I suspect a change (to something more redirection-friendly) would allow the user to get rid of them.
p:\mapm> echo %@eval[acos(2)] 2>NUL MAPM Warning: 'm_apm_arccos', |Argument| > 1 0
p:\mapm> grep Warning: *.c MAPMUTL1.C: fprintf(stderr, "MAPM Warning: %s\n", message);