I find it often helps to write small test scripts to figure out how to solve a specific problem. They often look something like:

use strict;  
use warnings;

while (<DATA>) {
    next if ! /PP: \((\d+)\)/;
    print "Matched $1\n";
}

__DATA__
PP: (899040) Jane Smith
[download]

where the __DATA__ section contains a selection of different lines to exercise the match.