Alias /trac "/usr/share/trac/htdocs"
        <LocationMatch "/.+/projects">
               SetHandler mod_python
               PythonHandler trac.web.modpython_frontend 
               PythonOption TracEnvParentDir /home/trac/projects
               PythonOption TracUriRoot /projects
        </LocationMatch>

        <LocationMatch "/.+/projects/$prjname">
               SetHandler mod_python
               PythonHandler trac.web.modpython_frontend 
               PythonOption TracEnvParentDir /home/trac/projects/$prjname
               PythonOption TracUriRoot /projects/$prjname
        </LocationMatch>