use Benchmark; my $str = 'hello'; timethese( 10000000, { 'pack' => q{ $str = pack("A10",$str); }, 'sprintf' => q{ $str = sprintf("%-10s",$str); }, }); #### Benchmark: timing 10000000 iterations of pack, sprintf... pack: 18 secs (16.86 usr 0.00 sys = 16.86 cpu) sprintf: 18 secs (17.36 usr 0.00 sys = 17.36 cpu)