# Pastebin XbfFizxy
class Actual {
        has Iterator    $.rest is required
}

class TurnOffIterator does Iterator {

        has Iterator    $.orig;
        has Iterator    $!actual;
        has             $.cond          = { True };

        method pull-one {
                with $!orig {
                        my \r = .pull-one;
                        say "orig: ", r;
                        return r if r =:= IterationEnd or r !~~ Actual;
                        $!orig = Nil;
                        $!actual = r.rest;
                        return self.pull-one
                } else {
                        my \r = $!actual.pull-one;
                        say "actual: ", r;
                        return r if r =:= IterationEnd;
                        return r if r ~~ $!cond;
                        IterationEnd but Actual.new: :rest($!actual)
                }
        }
}

role CondSeq {
        method take-while($cond) {
                my $iter = $.iterator;
                Seq.new(TurnOffIterator.new: :orig(
                        $iter ~~ TurnOffIterator
                                ?? $iter
                                !! class :: does Iterator {
                                        method pull-one { Actual.new: :rest($iter) }
                                }.new 
                        ), :$cond, :take) but CondSeq
        }               
}