-# t/TEST will use -MTestInit. You may "use TestInit" in the test
-# programs but it is not required.
+# t/TEST and t/harness will invoke each test script with
+# perl -I. -MTestInit[=arg,arg,..] some/test.t
+# You may "use TestInit" in the test # programs but it is not required.
+#
+# TestInit will completely empty the current @INC and replace it with
+# new entries based on the args:
+#
+# U2T: adds ../../lib and ../../t;
+# U1: adds ../lib;
+# T: adds lib and chdir's to the top-level directory.
+#
+# In the absence of any of the above options, it chdir's to
+# t/ or cpan/Foo-Bar/ etc as appropriate and correspondingly
+# sets @INC to (../lib) or ( ../../lib, ../../t)
+#
+# In addition,
+#
+# A: converts any added @INC entries to absolute paths;
+# NC: unsets $ENV{PERL_CORE};
+# DOT: unconditionally appends '.' to @INC.
+#
+# Any trailing '.' in @INC present on entry will be preserved.