Adds example for classify refs #1731

doc/Type/Any.pod6

@@ -891,8 +891,23 @@ Defined as:
     multi sub classify($test, +items, :$into!, *%named )
     multi sub classify($test, +items, *%named )
 
-The two first forms will fail.
+The two first forms will fail. The rest include a C<$test>, which is a function
+that will return a scalar for every input; these will be used as keys of a hash
+whose values will be arrays with the elements that output that key for the test
+function.
 
+=for code
+my @years = (2003..2008).map( { Date.new( $_~"-01-01" ) } );
+@years.classify( *.is-leap-year , into => my %leap-years );
+say %leap-years;
+# OUTPUT: «{False => [2003-01-01 2005-01-01 2006-01-01 2007-01-01], 
+#           True => [2004-01-01 2008-01-01]}␤»
+
+
+Similarly to L<C<.categorize>|/type/Any#method_categorize>, elements can be
+normalized by the C<Callable> passed with the C<:as> argument, and it can use
+the C<:into> named argument to pass a C<Hash> the results will be classified
+into; in the example above, it's defined on the fly.
 
 =head2 method produce