demark(d, L)
i1 : demark("+", a..f) o1 = a+b+c+d+e+f
i2 : demark(" and ", 6:"more") o2 = more and more and more and more and more and more
To achieve a similar insertion while keeping the output as a list, see mingle.
i3 : mingle(6: "more", 5: "and") o3 = {more, and, more, and, more, and, more, and, more, and, more} o3 : List
The object demark is a function closure.