Add an initial string so that the code example runs

S32-setting-library/Str.pod

@@ -442,6 +442,7 @@ this case the entire rest of the string is returned, whatever is available.
 A version of C<substr> that returns a writable reference to a part of a
 string variable:
 
+ my $string = "one of the characters in the Flinstones is: barney";
  $string ~~ /(barney)/;
  substr-rw($string, $0.from, $0.to) = "fred";