flexfax: dialrules - empty string match?

["Mau, Jonathan" <Jonathan.Mau@nrc.ca>]

Greetings:

The source of FAX numbers in my organization is not clean (ie the user
interface is dumb enough to allow email address to be entered into the FAX
number field), so sometimes when running through the rules, an empty string
results.  I want to match these and send them to an internal number.  I have
tried the following regular expressions to match on the empty string, but
none work:

^$
.?
[^.]
.{0,1}

How do I match to an empty string?

Thanks

Jonathan