[Exim] Two questions regarding virtual domain aliases...

I'm planning on using the virtual domain aliasing feature in Exim via the "file=/etc/aliases/$domain" thing. However, I have two questions:

1) What if I want to have the same aliases for 'client.com' and 'mail.client.com'. Do I have to use a symlink in /etc/aliases, or is there some way to tell Exim "treat all subdomains of 'client.com' as just 'client.com'"

2) I know that Exim supports a default alias, via "*: defaultcontact@???". However, can I use regexps? For example, if I want to have "help" and "helpdesk" and "helpcenter" all go to the same person, I'd like to be able to say "help.*: jhelper@???". Can Exim do that?

- Joe