@lace(t:tab, n:numeric)

builds a new tab whose elements are interlaced sequences of the elements of the t subcollections, up to size n.
       @lace([[1, 2, 3], 6, ["foo", "bar"]], 9)

returns
       [1, 6, "foo", 2, 6, "bar", 3, 6, "foo"]

the first elements is taken in the first element of t, the second in the second element of t, etc., in a cyclic way, until 9 elements have been acquired. Scalar elements are extended to tab of constants and element in a subcollection are taken modulo the size of the subcollection.