Treating result of subselect as row

Hi,

If I have a subselect that returns one row, then how can I use this in
expressions that expects row constructors in the operands, like OVERLAPS or
IN ?

SELECT (subselect1) OVEPLAPS (subselect2) -- both subselect returns one
row and two columns

OR:

SELECT (SubselectWithOneRow) IN (subselect2) -- but here subselect2 may
return many rows, but column counts are equal

I tried these in 8.2 without success.

Thanks,
Otto