use Time::HiRes 'time'; my $t = time; # the whole script here say time - $t; MCE::Flow->finish; say time - $t; __END__ 1 worker: 6.01482510566711 7.76495599746704 2 workers: 4.12953305244446 7.07751798629761 4 workers: 3.33010196685791 8.4802930355072 #### _cache_collatz( $_ ) for 1 .. 1e6; say scalar %cache; %cache = (); _cache_collatz( $_ ) for 1 + 4e5 .. 1e6; say scalar %cache; __END__ 2168611 2168611