should be B<TRUE> or B<FALSE>. Additionally B<TRUE>, B<true>, B<Y>,
B<y>, B<YES>, B<yes>, B<FALSE>, B<false>, B<N>, B<n>, B<NO> and B<no>
are acceptable.
=item B<NULL>
should be B<TRUE> or B<FALSE>. Additionally B<TRUE>, B<true>, B<Y>,
B<y>, B<YES>, B<yes>, B<FALSE>, B<false>, B<N>, B<n>, B<NO> and B<no>
are acceptable.
=item B<NULL>