Vice versa. Look at the Rate column — it shows the speed of the function! The more times a second the function is called, the faster it is :) So in this table (produced by the benchmark involving all three variants) 
                   Rate      interval   HiRes::time buitin time()
interval        88470/s            --          -53%          -95%
HiRes::time    188363/s          113%            --          -89%
buitin time() 1753092/s         1882%          831%            --

[download]
builtin time() is 9 times faster than Time::HiRes::time, which is nearly 2 times faster than the weird variant with tv_interval!

Benchmark code is here: 

#!/usr/bin/perl

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

# Use Perl code in strings...
cmpthese(-1, {
        'interval' => sub { my $t0 = [Time::HiRes::gettimeofday];
                         my $elapsed = Time::HiRes::tv_interval($t0)}
        ,
        'HiRes::time' => sub { my $t0 = Time::HiRes::time();
                         my $elapsed = Time::HiRes::time() - $t0;
        },
        'buitin time()' => sub { my $t0 = time;
                         my $elapsed = time - $t0;
        },
    });

[download]
     s;;Just-me-not-h-Ni-m-P-Ni-lm-I-ar-O-Ni;;tr?IerONim-?HAcker ?d;print

In reply to Re^3: Measuring time intervals using Time::HiRes -- time vs. gettimeofday and tv_interval by Ieronim
in thread Measuring time intervals using Time::HiRes -- time vs. gettimeofday and tv_interval by hrr

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