use Set::Light; my $pid = fork; die "Can't fork: $!" if ! defined $pid; if($pid){ # parent my $start_time = time; wait; printf "Child exited after %d seconds\n", time - $start_time; } else { # child my $start_time = time; my $set = Set::Light->new(); for( my $i = 0; $i < 10_000_000; $i++ ) { $set->insert( $i ); } printf "Child done after %d seconds\n", time - $start_time; exit; } __END__ Child done after 36 seconds Child exited after 163 seconds