use Test; my &uniq = *.Bag.first(*.value == 1).key; is (3, 3, 1).&uniq, 1; is (3, 2, 4, 2, 4).&uniq, 3; is (1).&uniq, 1; is (4, 3, 1, 1, 1, 4).&uniq, 3;