Mention one use case of exec() (#37982)

files/en-us/web/javascript/reference/global_objects/regexp/exec/index.md

@@ -52,6 +52,8 @@ When using `exec()`, the global flag has no effect when the sticky flag is set 
 - If you are finding all occurrences of a global regex and you don't care about information like capturing groups, use {{jsxref("String.prototype.match()")}} instead. In addition, {{jsxref("String.prototype.matchAll()")}} helps to simplify matching multiple parts of a string (with capture groups) by allowing you to iterate over the matches.
 - If you are executing a match to find its index position in the string, use the {{jsxref("String.prototype.search()")}} method instead.
 
+`exec()` is useful for complex operations that cannot be easily achieved via any of the methods above, often when you need to manually adjust [`lastIndex`](/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp/lastIndex). ({{jsxref("String.prototype.matchAll()")}} copies the regex, so changing `lastIndex` while iterating over `matchAll` does not affect the iteration.) For one such example, see [rewinding `lastIndex`](/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp/lastIndex#rewinding_lastindex).
+
 ## Examples
 
 ### Using exec()