> ri Enumerable
The +Enumerable+ mixin provides collection classes with several
traversal and searching methods, and with the ability to sort. The
class must provide a method +each+, which yields successive members
of the collection...

> ri String.each
Splits _str_ using the supplied parameter as the record separator
(+$/+ by default), passing each substring in turn to the supplied
block.

Okay, so maybe String shouldn't mixin Enumerable in the first place.