Here's a test that should exercise every version of "pydoc" installed on the system:

mkdir -p /tmp/foo/bar; cd /tmp/foo; chmod 0 bar
for n in `whereis -b pydoc`; do echo "**** $n ****"; $n modules; done

Tested under Ubuntu with bash and sh; should work fine with any Bourne-derived shell that supports 'whereis'. Please see attached file.