pgshell, a very simple perl program which was built to help with Gimp. Gimp has a perl server so having a command line where you can type perl commands and have them execute in the Gimp's image processing windows is the best way to confirm whether things will work as you expect them to. It is basically just using Term::Readline and an eval block. I modified it for my own use to let you type/paste in a several line long perl program or code block using start and end tags.