String.Chars for lists is implemented to consider the lists as a list of unicode code points.
The 87 represents the W you see represents the at the beginning of the line, the 13 (Carraige return) causes that it is printed at the beginning of the line.
23, 6, 3, 2, and 1 are some other kind of control characters, usually ignored by modern terminals.
If you want to see the list you need to use inspect, within the interpolation, eg. IO.puts("l1: #{inspect(l1)}").
