Adds RUN-MAIN refs #2632

doc/Language/create-cli.pod6

@@ -325,6 +325,42 @@ yourself, or by importing one from any of the
 L<Getopt|https://modules.perl6.org/search/?q=getopt> modules available in the
 ecosystem.
 
+X<|RUN-MAIN>
+=head2 sub RUN-MAIN
+
+Defined as:
+
+    sub RUN-MAIN(&main, $mainline, :$in-as-argsfiles)
+
+This routine allows complete control over the handling of C<MAIN>.  It gets a
+C<Callable> that is the MAIN that should be executed, the return value of the
+mainline execution  and additional named variables: C<:in-as-argsfiles> which
+will be C<True> if STDIN should be treated as C<$*ARGFILES>.
+
+If C<RUN-MAIN> is not provided, a default one will be run that looks for
+subroutines of the old interface, such as C<MAIN_HELPER> and C<USAGE>.  If
+found, will execute following the "old" semantics.
+
+=begin code
+class Hero {
+    has @!inventory;
+    has Str $.name;
+    submethod BUILD( :$name, :@inventory ) {
+        $!name = $name;
+        @!inventory = @inventory
+    }
+}
+
+sub new-main($name, *@stuff ) {
+    Hero.new(:name($name), :inventory(@stuff) ).perl.say
+}
+
+RUN-MAIN( &new-main, Nil );
+=end code
+
+This will print the name (first argument) of the generated object.
+
+
 X<|GENERATE-USAGE>
 =head2 sub GENERATE-USAGE