OK, just to confirm - does the Perlmonks community agree that Perl threads are actually runnable on separate CPUs/cores? Can anybody tell me on how to check that separate Perl threads are running on different cores in case "top is foolong you" as suggested already? I did a test to measure the time it takes to run a single process that processes all data and then another test for 8 Perl threads that each process 1/8 of the data set and the time measurement was almost exactly the same. I am doing something wrong?