Yes.

use Math::BigApprox qw/Fact/;
use Benchmark qw/cmpthese/;
use Memoize;

memoize( 'Fact', INSTALL => 'fastFact' );

our $test = 20000;

print "$test!\t=>\t", Fact($test), "\n";

cmpthese ( -5, {
    Fact        => sub{ my $a = Fact($test)     },
    fastFact    => sub{ my $a = fastFact($test) },
} );
[download]

Results...

20000!  =>      1.819206e+77337
             Rate     Fact fastFact
Fact       7.89/s       --    -100%
fastFact 297159/s 3766395%       --
[download]

You almost need Math::BigApprox to deal with the percent improvement when memoized. A factorial is one of those "pure functions" where memoization pays off if you intend to use the same params more than once.