Simple variable question

In a screen scraping session I capture a URL using ~@SITE_URL@~ in an extractor pattern.

I then invoke a script from that extractor screen that executes "after each pattern match". Within the script when I reference SITE_URL using getVariable it shows SITE_URL as being null. I would like to use the contents of SITE_URL as
~#SITE_URL#~ for my next scrapable file URL, but can't because it is null even though the original scraping file filled it in.

thanks for the help