This script can pose as a web browser, visit a web site, extrapolate content, modify it, and then feed it back to a user on your site. Using a search and replace routine, you can tell the script exactly what to look for and what to put in it's place.
This script fetches a URL that has been typed into the form and then mangles the contents of it, displayed a resulting page showing the original page jumbled up.
Grab another site's content and put it on yours using this script. No SSI required.