Next paragraph is an excerpt from documentation inside Pari.pm:

This package is a Perl interface to famous library PARI for
numerical/scientific/number-theoretic calculations.  It allows use of
most PARI functions as Perl functions, and (almost) seamless merging
of PARI and Perl data. 

Documentation to this package is contained inside Pari.pm. After
installing it is accessible by standard means, like

  perldoc Math::Pari
  man Math::Pari

and possibly in other forms particular for your system.

If you have a not very old perl (5.003 should do), then uncompress the
archive into a separate directory, find the archtecture of your
processor (if it is not recognized automatically, the slower portable
code will be used), and do

	perl Makefile.PL 
		or
	perl Makefile.PL machine=hppa

(recognized processors are sun3 sparcv7 sparcv8micro sparcv8super
alpha hppa i386), then

	make
	make test

(expect several failures from will_fail.t, but Pari.t and Testout.t
should pass). Now

	make install

should make this extension available to the perl programs.

You can get a better undestanding of the translations made by Testout.t by
running it manually:

	perl t/Testout.t

after install, or

	perl -Mblib t/Testout.t

before install.
