I activly use the following code in spec files:

%define test1 0
%define test2 0
%prep
%build

%if %{test1}
%if %{test2}
%else
%endif
%endif

That works ok with rpm 3.0.4-0.48 but fails with 3.0.5-9.6x. The error
message is:
parse error in expression
(spec file name):(%if %{test1} line number): parseExpressionBoolean returns
-1

The same script works fine if test1 == 1...