ghc iftestcase.ll.hs

./a.out runall | perl iftestcase-perl.pl

will create 9240 testcase instances in the current directory exploring
various combinations of `define `ifdef `ifndef `elif `else

As of version 10010, they all passed.  Five of them (namely
ifdef4891.bsv ifdef7672.bsv ifdef2556.bsv ifdef5991.bsv ifdef7720.bsv)
have been selected mostly at random and are placed in this directory.