Once upon a time, Apple's Mac OS operating system and the Unix operating system were two completely separate worlds, each with its own idea of what constituted "scripting." On Mac OS, there was AppleScript and the OSA. On Unix, there was the command line, shell scripting, and the various shell scripting languages such as Perl. Now, with Mac OS X, those two worlds are united; both kinds of "scripting" are present, and there is communication between them, in both directions. Thus, you can combine the power of Unix scripting with the power of AppleScript.
The way you call a Unix tool from AppleScript is with the do shell script scripting addition command. The way you call from Unix into AppleScript is with the osascript tool. This chapter discusses both, along with some examples; you'll see how Perl, curl, and AppleScript can work together to perform a web query, and you'll see Ruby, AppleScript, and Microsoft Excel joining forces to perform textual analysis and graph the results.