this seems to be a good day for me to be finding old bugs. i don't think these two bits of rc should behave any differently:
% rc -c 'echo hello > /fd/4' <>[4] /dev/cons
hello
% {echo hello > /fd/4} <>[4] /dev/cons
/fd/4: rc: can't open: '/fd/4' inappropriate use of fd
%
as it happens, the actual file being opened in the second
instance is '#c/cons' (the original rc's stdin).
