reap program with prunehistory

[Julien ÉLIE]

Hi,

According to the man page of prunehistory:

-p
  Prunehistory will normally complain about lines that do not follow
  the correct format.  If the ``-p'' flag is used, then the program
  will silently print any invalid lines on its standard output.
  (Blank lines and comment lines are also passed through.)  This can
  be useful when prunehistory is used as a filter for other programs
  such as reap.

What is reap?  An old program shipped with INN?
Another Unix program?  (I couldn't find it with Debian "apt-file search".)

I am currently converting the man page into POD and I wonder what is
the meaning of the last sentence.

-- 
Julien ÉLIE

« La vérité pure et simple est très rarement pure
  et jamais simple. » (Oscar Wilde)