[Zope] string manipulation problem

[Greg]

I simply need to remove the leading x amount of characters from a string.  
I have a username that looks like this:

ADOMAIN\jsmith

This is on my NT network of course.  I would like to display only:

jsmith

I tried using string.split, but I keep receiving errors.

This is the code I am trying now.

<dtml-call "REQUEST.set('authU', _.string.split(AUTHENTICATED_USER, 
'\\')[-1])">
<dtml-var authU>

I'll be using that variable elseware too.

Thanks for you help!

Greg