We are using Perl 5.10.1. I have just had a look at the delta documentation. Apparently, there is a big upgrade of the `Test::Harness` module (which provides the `prove` command) between 5.10.0 and 5.10.1, and it does look like that the `-j N` option is only added as part of this upgrade, which is a bit unfortunately.

(By the way, the current stable version of Perl is 5.18.0, so we are all far behind!)

See also [perl5101delta](http://perldoc.perl.org/perl5101delta.html).

@arjclark To test for Perl 5.10.1, you can do:

```sh
if perl -e 'require 5.10.1' 2>/dev/null; then
    prove -j 9 # ...
else
    prove # ...
fi
```