use Time::HiRes qw(time); 
use Benchmark qw(:hireswallclock cmpthese); 

cmpthese(5, { 
    a => sub { sleep 4 }, 
    b => sub {sleep 6}
});'

#            (warning: too few iterations for a reliable count)
#            (warning: too few iterations for a reliable count)
#                Rate  a  b
#a 5000000000000000/s -- 0%
#b 5000000000000000/s 0% --