Can I create a regex that matches an optional parameter?

[BR Brett Ryan (3456)]

I'd like to create the following definition:

    <definition name="REGEXP:home(\.(mob|tab))?" extends="layout{1}"/>

Which I have three layouts, layout, layout.mob and layout.tab.

I'd like this definition to match "layout" if "home" is accessed, but I get an 
NPE.

The mob and tab variants do work.