unexpected output from a simple Elixir function

unexpected_output

/**
* Why does certain input result in weird character output rather than a list?
* (from the Exercise: Functions-1 - Pragprog Elixir book)
**/

iex> pair_tuple_to_list = fn {a, b} -> [a, b] end
#Function<6.90072148/1 in :erl_eval.expr/5>

iex> pair_tuple_to_list.({1, 4})
[1, 4]

iex> pair_tuple_to_list.({8, 9})
'\b\t'   

iex> pair_tuple_to_list.({8, 19})
[8, 19]

iex> pair_tuple_to_list.({18, 9})
[18, 9]

iex> pair_tuple_to_list.({7, 9})
'\a\t'  

iex> pair_tuple_to_list.({8, 7})
'\b\a'

iex> pair_tuple_to_list.({2, 8})
[2, 8]