+exim -odf -DOPT=relative_file_path d@test.ex
+Subject: test 1.4 - Specified, non-absolute
+****
+exim -odf -DOPT='$acl_m_unset' e@test.ex
+Subject: test 1.5 - Specified, expansion empty
+****
+exim -odf -DOPT='DIR/aux-fixed/TESTNUM.$sender_address' f@test.ex
+Subject: test 1.6 - Specified, expansion tainted
+****
+exim -odf -DOPT='${if ={0}{0} {DIR/aux-fixed/TESTNUM.bounce.tmpl}{bad}}' g@test.ex
+Subject: test 1.7 - Specified, expansion good
+****