[jboss-dev] Determining JBoss AS server version by examining install

I need to determine from an ant script whether the JBoss AS version installed in a particular directory is JBoss AS 4.2.0 or later. Initially I thought I could just look at the JBOSS_HOME env entry, but the user might have installed it in a different directory other than the default jboss-4.2.0.GA directory. Can anyone think of a good/recommended way to do this? Is there a file somewhere in the distro I can parse?