Understanding network-side scripting

We all understand the lines in the sand (or the architectural diagram) that separate client-side scripting from server-side scripting. It's very clear that client-side scripting, e.g. JavaScript, VBScript, ActionScript, executes on the client while server-side scripting, e.g. PHP, ASP, executes on the server. But what about network-side scripting? "There is no such thing!" might be the first response to this question, but I beg to disagree. Programmable proxies, a la F5's BIG-IP Local Traffic Manager, that provide a scripting language such as iRules, are simultaneously client-side and server-side, with the best definition to describe their placement in architectures being network-side...