Suggest none-junction, explain why !/…/ works

Hopefully resolves #1425.

Author: AlexDaniel

doc/Type/List.pod6

@@ -309,6 +309,26 @@ Examples:
     say ('hello', 1, 22/7, 42, 'world').grep: Int;              # OUTPUT: «(1 42)␤»
     say grep { .Str.chars > 3 }, 'hello', 1, 22/7, 42, 'world'; # OUTPUT: «(hello 3.142857 world)␤»
 
+
+Note that if you want to grep for elements that do not match, you can
+use a C<none>-L<Junction|/type/Junction>:
+
+    say <a b 6 d 8 0>.grep(none Int);           # OUTPUT: «(a b d)␤»
+    say <a b c d e f>.grep(none /<[aeiou]>/);   # OUTPUT: «(b c d f)␤»
+
+Another option to grep for elements that do not match a regex is to
+use a block:
+
+    say <a b c d e f>.grep({! /<[aeiou]>/})     # OUTPUT: «(b c d f)␤»
+
+The reason the example above works is because a regex in boolean
+context applies itself to C<$_>. In this case, C<!> boolifies the
+C«/<[aeiou]>/» regex and negates the result. Smartmatching against a
+L<Callable> (in this case a L<Block>) returns the value returned from
+that callable, so the boolified result of a regex is then used to
+decide whether the current value should be kept in the result of a
+grep.
+
 The optional named parameters C<:k>, C<:kv>, C<:p>, C<:v> provide the same
 functionality as on slices:
 
@@ -338,12 +358,6 @@ Examples:
     say grep { .Str.chars > 3 }, :p, 'hello', 1, 22/7, 42, 'world';
     # OUTPUT: «(0 => hello 2 => 3.142857 4 => world)␤»
 
-Note that if you want to grep for elements that do not match a regular
-expression, you should use the following syntax, with a block:
-
-    say <a b c d e f>.grep({! /<[aeiou]>/})
-    # OUTPUT: «b c d f␤»
-
 =head2 routine first
 
 Defined as: