Using regular expressions within xpath predicates

Can anyone share an example of using regular expressions within an xpath
predicate?  I'm wanting to parse a structure and pick out any elements
that have a non-numeric name.  Example:

<security>
	<policies>
		<policy>
			<name>randy</name>
			...
		</policy>
		<policy>
			<name>1</name>
			...
		</policy>
		<policy>
			<name>policy 101</name>
			...
		</policy>
		<policy>
			<name>3</name>
			...
		</policy>


I'm trying to figure out what xpath expression would identify the
policies with alpha characters...  Something like:

not(/security/policies/policy[name=[0-9]*])

Thanks,

Randy