I often play around with Ruby code to try things out. irb is of course a great Ruby interactive shell for this. However, what it's less good at is multi-line code, or more complicated code, and simply refining code that you execute over and over (in particular when it's multi-line). Solution: use TextMate instead. As TextMate users know, you can run arbitrary script (either a selection or a file's worth). I am finding now that I much prefer to simply pop open a new window in TextMate, and type my experiments there, and then hit Cmd-R to try things out. It even produces nicer output.