In order to test that our extension works, we now need to look at the file test.pl.  This file is set up to imitate the same kind of
       testing structure that Perl itself has.  Within the test script, you perform a number of tests to confirm the behavior of the exten-
       sion, printing "ok" when the test is correct, "not ok" when it is not.  Change the print statement in the BEGIN block to print
       "1..4", and add the following code to the end of the file:

               print &Mytest::is_even(0) == 1 ? "ok 2" : "not ok 2", "\n";
               print &Mytest::is_even(1) == 0 ? "ok 3" : "not ok 3", "\n";
               print &Mytest::is_even(2) == 1 ? "ok 4" : "not ok 4", "\n";

       We will be calling the test script through the command ""make test"".  You should see output that looks something like this:

               % make test
               PERL_DL_NONLAZY=1 /opt/perl5.004/bin/perl (lots of -I arguments) test.pl
               1..4
               ok 1
               ok 2
               ok 3
               ok 4
               %