module to skip tests when modules are not available

 Test::Needs allows one to skip test scripts if modules are not available. The
 requested modules will be loaded, and optionally have their versions checked.
 If the module is missing, the test script will be skipped. Modules that are
 found but fail to compile will exit with an error rather than skip.
 .
 If used in a subtest, the rest of the subtest will be skipped.
 .
 If the "RELEASE_TESTING" environment variable is set, the tests will
 fail rather than skip. Subtests will be aborted, but the test script
 will continue running after that point.