use Benchmark;

timethese( 10000000, {
  5 => sub {my $R = 5;},
  6 => sub {my $R = 6;}
});

##</code><code>##

    5:  6 wallclock secs ( 6.61 usr + -0.03 sys =  6.58 CPU) @ 1519756.84/s
    6:  6 wallclock secs ( 5.89 usr +  0.08 sys =  5.97 CPU) @ 1675041.88/s