REPLs often provide a way to access the last processed value, in the Chrome Dev
Tools, it's $_, in the Node.js or Ruby REPLs, it's _. In IEx, the last
processed value is retrieved by v/0:
iex(1)> 1
1
iex(2)> v
1
iex(3)> v |> Kernel.+(1)
2
Additionally, there is v/1 to retrieve the nth value from history. In IEX, use
h/0 or h/1 for more details.