Ruby docs rindex example

Question

This example is from the ruby docs.

"hello".rindex(/[aeiou]/, -2)   #=> 1

Why does this output 1 instead of 4?

Answer 1

Because the second parameter. From the doc

If the second parameter is present, it specifies the position in the string to end the search—characters beyond this point will not be considered.

So

"hello".rindex(/[aeiou]/)
 => 4