By Benchmark, the second one is faster than the first code. If think you could benchmark you code with both code to be sure.

use Time::HiRes qw(time);
use Benchmark qw(:all) ;

# Use Perl code in strings...
cmpthese(-10, {
        'Hires' => sub { my $t0 = [Time::HiRes::gettimeofday];
                         my $elapsed = Time::HiRes::tv_interval($t0)}
        ,
        'Time' => sub { my $t0 = time;
                         my $elapsed = time - $t0;
        },
    });
[download]

... result ...

           Rate Hires  Time
Hires 100260/s    --  -58%
Time  240043/s  139%    --
[download]