add example of in-place editing of a hash key

also shows how to delete a hash key which seems to be missing

Author: tbrowder

doc/Language/hashmap.pod6

@@ -462,9 +462,34 @@ specify that you would like read-write access to the values.
     my %answers = illuminatus => 23, hitchhikers => 42;
     for %answers.values -> $v is rw { $v += 10 };
 
-It is not, however, possible to do in-place editing of hash keys, even in the
-case of object hashes.
+It is not possible directly to do in-place editing of hash keys, even in the
+case of object hashes; however, a key can be deleted and a new key/value pair
+added to achieve the same results. For example, given this hash:
 
+=begin code
+my %h = a => 1, b => 2;
+for %h.keys.sort -> $k {
+    # use sort to ease output comparisons
+    print "$k => {%h{$k}}; ";
+}
+say ''; # OUTPUT: «a => 1; b => 2;»␤
+=end code
+
+replace key 'b' with 'bb' but retain 'b's value as the new key's value:
+
+=begin code
+for %h.keys -> $k {
+    if $k eq 'b' {
+        my $v = %h{$k};
+        %h{$k}:delete;
+        %h<bb> = $v;
+    }
+}
+for %h.keys.sort -> $k {
+    print "$k => {%h{$k}}; ";
+}
+say ''; # OUTPUT: «a => 1; bb => 2;»␤
+=end code
 
 =end pod