Elaborate a bit on substr-rw()

S32-setting-library/Str.pod

@@ -471,6 +471,17 @@ string variable:
  $string ~~ /(barney)/;
  substr-rw($string, $0.from, $0.to) = "fred";
 
+This writable reference can be aliased to, for repeated operations:
+
+ my $r := substr-rw($string, $0.from, $0.to);
+ $r = "fred";   # "barney" replaced by "fred"
+ $r = "wilma";  # "fred" replaced by "wilma"
+
+Please note that only the start point is kept by the reference: any changes
+to the length of the string before the start point, will render the reference
+useless.  So it is probably safest to keep only one writable reference per
+string, or make sure that all replacement strings have the same size.
+
 =item trim
 
   multi method trim() is export;