cleanup, docs

site/doc/pages/substr.txt

@@ -20,7 +20,6 @@ If `start_pos` is negative, counting starts from the end of the string.
 
 If `length` is negative, the returned range stops that many bytes before the end of the string.
 
-Related:
 
-- PHP: `substr()`
-- JavaScript / Node.js: `String.prototype.slice()` or `substring()`
+:example
+print(substr("documentation", 0, 3), "\n");