[arekm@tarm ~/rpm/SPECS]$ cat alien.spec
# $Revision: 1.72 $, $Date: 2007/02/12 21:23:46 $
Summary:        Pakages converter (tgz, rpm, deb, slp)
Name:           alien
Version:        1.0
Release:        1
Group:          nothing
License:        nothing

%description

%package        x
Summary:        x
Version:        2.0
Group:          nothing
%prep

%description x

%build

%install

%clean
rm -rf $RPM_BUILD_ROOT

%files
[arekm@tarm ~/rpm/SPECS]$ rpmbuild --define "prep %dump" alien.spec 2>&1 | grep ": PACKAGE_VERSION"
 -1: PACKAGE_VERSION    2.0