use strict;
use warnings;
use Benchmark 'cmpthese';

my (%set_a, %set_b);
@set_a{1..100} = undef;
@set_b{50..150} = undef;

sub slices {
  my %set;
  @set{keys %set_a, keys %set_b} = undef;
}

sub items {
  my %set;
  $set{$_} = undef for keys %set_a, keys %set_b;
}

sub hasheq {
  my %set;
  %set = (%set_a, %set_b);
}

cmpthese(10000, {
  slices => \&slices,
  items  => \&items,
  hasheq => \&hasheq,
});