#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
use feature 'say';
use Time::HiRes qw(gettimeofday tv_interval);

# measure elapsed time
say 'Start counting';
my $t0 = [gettimeofday];
# do bunch of stuff here
say 'I am doing my things here that I want to know the process time...';

my $t1 = [gettimeofday];
say 'Finished counting';

print Dumper $t0;
print Dumper $t1;

my $t0_t1 = tv_interval $t0, $t1;
say $t0_t1;

my $elapsed = tv_interval ($t0, [gettimeofday]);

say $elapsed;

# $elapsed = tv_interval ($t0); # equivalent code

__END__

$ perl test.pl
Start counting
I am doing my things here that I want to know the process time...
Finished counting
$VAR1 = [
          1507287063,
          951261
        ];
$VAR1 = [
          1507287063,
          951274
        ];
1.3e-05
8.6e-05