You can use wildcards/regexes in lists only.
They are not possible in Extended lists for recategorization. Extended lists cannot contain wildcards.
I did try and was successful with leaving off part of the URL of a site to recategorize. For example:
Just a helpful hint!
The Extended list will work on the domain level and categorize the sub-hosts.
However, It won't let you do wildcards like:
google.* in order to get google.com, google.ca, google.de, google.cn, etc.