The following patch against 21092 to configpm only has one change: my $summary becomes our $summary : unique causing the perl-V output to not be copied between threads. This saves about 1.5K per thread, as can be seen from the Benchmark::Thread::Size output: before # (ref) 0 2184 1 2588 ± 4 2 2914 ±16 5 3853 ±18 10 5426 ±20 20 8554 ±14 50 17972 ±36 100 33616 ±62 Config.pm summary -> unique # (ref) 0 2184 1 2585 ± 6 2 2903 ±16 5 3842 ±16 10 5405 ±20 20 8531 ±24 50 17885 ±24 100 33484 ±42 Liz