use Time::HiRes qw(tv_interval);

&t('Reference Time');
sleep(2);
&t('Did something');

sub t(){
    my $t0 = [gettimeofday];
    my $elapsed = tv_interval ( $t0 );
    my $elapsed_o = $elapsed;
    
    $elapsed = $elapsed - $last_elapsed;
    if ($last_elapsed){printf ("(%s)%f<br>\n",$_[0],$elapsed);}
    $last_elapsed = $elapsed_o;
}