A wise man once said: "Prediction is hard, especially about the future."

A look into the source of Iterator shows, that it is implemented as you described (one value look ahead internally).

Doing it this way seems questionable.

Update: It seems that he needs the look ahead to be able to return undef as a valid value telling it apart from Iterator-exhausted.

So maybe you are better of with Iterator::Simple which cannot yield undef, but will also not look ahead.