$x = $y * 16;
$x = $y << 4; #Much faster

##</code><code>##

use Benchmark;
use integer;
Benchmark::cmpthese(-10, {
 multiply => sub { my $y = 3; my $x = $y * 16 },
 shift => sub { my $y = 3; my $x = $y << 4 } }
);