Install new perl test function in PostgreSQL

Hi,

I have taken below perl example form PostgreSQL documentation Chapter: 40.1

CREATE FUNCTION perl_max (integer, integer) RETURNS integer AS $$
if ($_[0] > $_[1]) { return $_[0]; }
return $_[1];
$$ LANGUAGE plperl;

I understood everything but I don't know how to integrate/install this new
function with PostgreSQL so that when I run "select perl_max(1,2)" query, it
returns 2. I have PostgreSQL install on one of my UNIX Server and has root
privileges. Please help me to install this function.

Thanks,
Jignesh