The $_ variable provided by bash is always set to the last argument of the previous command. One handy use of this is for changing directories into a newly created directory.
$mkdirnew_dir&&cd$_
This command will leave you in your newly created directory, new_dir.
We can imagine using this bash variable in a number of similar scenarios as well. What if we are using some language specific command that creates a directory? Will it work when creating a new Phoenix or Rails project?