+1 for vim slime. It’s not only amazing for programming in REPL languages. Since you can send anything from the buffer to another pane, it can be used to execute commands (send some rows from a cookbook to a remote shell), copy and paste segments of a local file to a remote source, and lots of other things. It’s a great example of doing something simple (send selections to another tmux/screen pane) that can be used in all kinds of useful ways. Very much the unix philosophy.