The manpage of Perls prove tool says:
Options in .proverc are specified in the same way as command line options:
# .proverc --state=hot,fast,save -j9
This is not true, a rule specified as
--rules='par=**'
will work on the command line but is not recognized in the .proverc
file. In fact, adding this line to .proverc
will disable parallel testing for all files.