public package Foswiki::AggregateIterator public package Foswiki::AggregateIterator is a Foswiki::Iterator $unique is set, we try to not repeat values.
Warning: $unique assumes that the values are strings.
{filter} can be defined to be a sub that filters each entry. The entry will be ignored (next() will not return it) if the filter returns false.
{process} can be defined to be a sub to process each entry before it is returned by next. The value returned from next is the value returned by the process function.