A Regular Expression is a sequence of characters that define a search pattern. If you feel this is to difficult to grasps at this point we recommend watching the following video
Shortcuts uses the popularHandlebarsJS to configure complexer URLs. We've also added the regex helper. In the name, URL and POST Forms fields you can use Regular Expressions. You can use any of the available Zendesk Placeholders in the regex helper.
Create a track and trace Shortcut
http://www.dhl.com/en/express/tracking.html?AWB={{regex ticket.description "[a-zA-Z][a-zA-Z]-\d{4}-\d{4}-\d{2}"}}&brand=DHL
Find the Order ID with 8 numbers in the first comment and use that to search Stripe
https://dashboard.stripe.com/search/?query={{regex ticket.description "\d{12}"}}