Improve discussion and examples of programmatic use of class method n…

…ames (#4168)

+ provide more practical examples
+ add a cross-reference link so the curious can find the discussion

doc/Language/objects.pod6

@@ -378,15 +378,6 @@ returns:
 method Str { "⤷ $!origin\n$ⲧ$.notes()$!destination ⤶\n" }
 =end code
 
-Method names can be resolved at runtime with the C<.""> operator.
-
-=begin code
-class A { has $.b };
-my $name = 'b';
-A.new."$name"().say;
-# OUTPUT: «(Any)␤»
-=end code
-
 The syntax used to update C<$.notes> changed in this section with respect
 to the previous L<#Attributes> section. Instead of an assignment:
 
@@ -398,10 +389,12 @@ we now do a method call:
 =for code :preamble<my $trip>
 $trip.notes("First steps");
 
+X<Classes|Methods,overriding default accessors>
 Overriding the default auto-generated accessor means it is no longer
 available to provide a mutable container on return for an assignment.
 A method call is the preferred approach to adding computation and
-logic to the update of an attribute. Many modern languages can update
+logic to the update of an attribute (see 'programmatic use' of such calls
+in the following section). Many modern languages can update
 an attribute by overloading assignment with a “setter” method. While
 Raku can overload the assignment operator for this purpose with a
 L<C<Proxy>|https://github.com/Raku/roast/blob/master/S12-attributes/mutators.t>
@@ -411,6 +404,34 @@ L<weaker object oriented design|https://6guts.wordpress.com/2016/11/25/perl-6-is
 
 =head2 Class and instance methods
 
+X<Classes|Methods,programmatic use>
+Method names can be resolved at runtime with the C<.""> operator which
+enables programmatic use of such names. For example, since an
+attribute name is also a method, we can show attibute C<a>'s value by
+calling the C<a> method:
+
+=begin code
+class A { has $.a = 9 }
+my $method = 'a';
+A.new."$method"().say;
+# OUTPUT: «9␤»
+=end code
+
+A method with arguments may be called in a similar manner:
+
+=begin code
+class B {
+    has $.b = 9;
+    method mul($n) {
+        $!b * $n
+    }
+}
+my $method = 'mul';
+B.new."$method"(6).say;
+# OUTPUT: «54␤»
+=end code
+
+X<Classes|Methods,signatures>
 A method's signature can have an I<explicit invocant> as its first parameter
 followed by a colon, which allows for the method to refer to the object
 it was called on.