Javascript Execution

Hi,

I am working on a http agent which harvests various products and prices on
a number of websites. The problem I run into is that some sites use
javascript.

After downloading a web page from my perl script, what I want to do is:
1. Execute any existing javascript on the page.
2. Modify the page according to the javascript results.
3. Save the page to a local file.

Hence I want to do the exact thing that a normal web browser does but
instead of writing to a browser window the output shall be written to a file.

Does anyone know of any possible solution or hint?

All suggestions kindly appreciated!

Regards,
Erik Axelkrans