If you want to customize a promotion link in response to a user query, you can add $q to your promotion URL and/or your promotion title. For example, say you have a site where users can look up postal codes. Add $q to your promotion URL, like this:
http://www.example.com/postalcodes/$q
Next, add $q to your promotion title, like this:
Postal Code Lookup: $q
Now, if the user searches for 98102, Programmable Search Engine will replace $q with the user's query, and display the promotion URL like this:
http://www.example.com/postalcodes/98102
The title will be displayed as:
Postal Code Lookup: 98102
You can use $q for both regular expression and non-regular expression promotions.