Strip a dirname from a property that represents a path

[Eric Wood]

I have a property that is a path reference to a jar file and I want to
get the directory name for the element.  The task dirname works with a
file to set a property, but is there a simply solution to grabbing the
path to from a file.  I assume that I could use the ant-contrib
PropertyRegex task, but was thinking that there is a simpler more
elegant solution.  Any thoughts?
 
<property name="pmd.jar" value="/release/pmd/pmd/4.1/pmd-4.1.jar" />
 
what I want is a property for the "release/pmd/pmd/4.1" directory.
 
Thanks, Eric