Note how to do "not equal" with constraints

doc/cabal-package.rst

@@ -1477,8 +1477,20 @@ system-dependent values for these fields.
 
     Version constraints use the operators ``==, >=, >, <, <=`` and a
     version number. Multiple constraints can be combined using ``&&`` or
-    ``||``. If no version constraint is specified, any version is
-    assumed to be acceptable. For example:
+    ``||``.
+
+    .. Note::
+
+       To avoid package versions when there is no `not equal` operator, use
+       ``<`` and ``>`` in combination with the ``||`` operator. We might want to
+       do this to avoid a deprecated version or to skip versions. For example,
+       the `time =1.12.*` series depends on `base >=4.13 && <5` but
+       `time-1.12.3` bumps the lower bound on base to `4.14`. If we still want
+       to compile with a `ghc-8.8.*` version of GHC that ships with `base-4.13`,
+       then we can use `time >=1.12 && (time <1.12.3 || time >1.12.3)`.
+
+    If no version constraint is specified, any version is assumed to be
+    acceptable. For example:
 
     ::