[exim] Regular expressions with $header_to?

How can I differentiate b/w

1. poolrobert@???
2. 3cffejjdbjfipdnkkjiiooieomcjaa.robert@???
3. "Robert Nicholson" <robert@???>
4. robert@???

without using "is" ie. exactly comparison

I want to be able to canoncalize the address before the comparison.

in the above I want reject 1 & 2 but not 3 and 4