Iterator Operations

 sub mingle {
 my @iterator = @_;
 my $next = 0;
 sub {
 my $line = $iterator[$next]->();
 $next = ($next + 1) % @iterator;
 $line;
 }
 }

• Now if you have several iterators you can turn them into one:

 $new_it = mingle($it1, $it2, $it3);

• (Proper handling of EOF conditions is left as an exercise.)