Q:

dynamically modify HTTP POST data

I set up a squid proxy server, and I would like to monitor and modify certain HTTP POST requests before it goes out of squid.  What are my options?

A:

Take a look at the Squid page on Content Adaptation to find what you're looking for.  Those are valid options, although the only really good one is new in Squid 3.
Another option, and what I use personally for this, is to transparently redirect the request to a script which modifies it and then forwards the changed version to the original destination.

