apt-get install libprophet-perl
Prophet is currently undergoing rapid development however, so we recommend installing directly from Git if you can.
The following command will get you a copy of the source tree you can install:
git clone git://gitorious.org/prophet/prophet.git
Once you've downloaded Prophet, you can install it:
PERL_MM_USE_DEFAULT=1 perl Makefile.PL
In the hopefully unlikely event that Prophet doesn't pass its tests, please tell the developers about it so we can improve things.