my @elapse= (0);
my %total;
my %only;
 
sub sub
{
    push @elapse, 0;
    # ...
    my( $name, $time );
    $total{$name} += $time;
    $only{$name} += $time;
    $only{$name} -= pop @elapse;
    $elapse[-1] += $time;
}