for my $i (280 .. 320) {
    for my $j (680 .. 720) {
        for my $k (95 .. 105) {
            for my $l (30 .. 40) {
                my $hg = hypergeom($i, $j, $k, $l);
            }
        }
    }
}

##</code><code>##

39.11s   Without Memoize
35.25s   Memoize logfact only
38.40s   Memoize gammaln only
47.04s   Memoize hypergeom only