I noticed another long-standing bug (I think the final result is wrong):

 % foo=(1 2)
 % bar=3
 % print -l ${foo+$bar$foo}
 31
 2
 % print -l ${foo+$foo$bar}
 1 23

This is a case of the arrayness of the result being lost because the
non-array, $bar, came after the array, $foo.

Attached is a patch that fixes this by having multsub() only honor
mult_isarr as a flag that indicates that a single-item result was
really an array, not that a multi-item result should not be an array.

..wayne..