String interpolation with pipe

[sihui_io]

It turns out a |> "#{}" doesn’t mean we are actually interpolating a into the position of #{}

iex(71)> "a" |> "This is: #{}, and #{last}"
"aThis is: , and b"
iex(72)> "a" |> "This is: , and #{last}"
"aThis is: , and b"