use 5.012; use strict; use warnings; use Benchmark qw(:all); bench($_) for qw(10 100 1000 10000); sub bench { my ($max) = @_; my @vars = map {$_ => $_} 1..$max; say $max; cmpthese -1 => { 'no copy' => sub{ my @keys = map { $_%2 ? () : $var…