The terminal command !$ allows us to to retrieve the previous command in
a terminal session. This allows us to reference the previous commands and append/
prepend if to a new command instead of using ↑ and ↓ arrow keys.
For example, this can be used to solve a common elixir mini-problem:
Prepending iex -S in front of a command to pry open an elixir process
in iex session.
$ mix phx.server
....
....
$ iex -S !$ # Pressing return returns the following
$ iex -S mix phx.server
There are many other ways !$ can be used to make our lives easier!
Tip: Binding !$ to a tmux key is super helpful, instead of having to
type it every time