Add a few examples for Nil; jnthn++ for the 'evaporation' example

lib/Type/Nil.pod

@@ -9,6 +9,29 @@
 Represents an empty list in list context, and an undefined value in item
 context.
 
+C<Nil>, when assigned, evaporates into the type object of the type of the
+container you assigned it into.
+
+	my Int $x = 42;
+	$x = Nil;
+	$x.say;				# (Int)
+
+It is for this reason that assigning an untyped container as C<Nil> will result
+in an C<(Any)> object.
+
+	my $x = Nil;
+	$x.say;				# (Any)
+	my Int $y = $x;		# error:	Type check failed in assignment to '$y'; expected 'Int' but got 'Any'
+
+This is because an untyped container is C<Any> until proven otherwise, and
+the C<Nil> evaporates
+
+If you are looking for a variable which transforms objects into type objects
+when said variable appears on the RHS, you can type the container as C<Nil>.
+
+	my Nil $x;
+	my Str $s = $x;
+	$s.say;				# (Str)
 
 =head1 Methods