in reply to
How to write out a Perl script and run it in as few keystrokes as possible.
While this is perhaps particular to my programming style, I have a window open that runs a "runtests" script on a loop. Inside 'runtests' (a plain old sh script) I run whatever I'm working on (usually a perl script) and end with a 5 second delay.
This allows me to change the delay or even the script arguments without interrupting the test loop script.
I find it's a remarkably handy way of keeping focus in the editor and looking over to see if tests are failing or the script is blowing up.