#!/usr/bin/perl

use strict;
use warnings;

my %hash;
$hash{$_}=1 for 1 .. 10_000_000;

__END__

##</code><code>##

#!/usr/bin/perl

use strict;
use warnings;
use constant KEYS => 10_000_000;

my %hash;
keys %hash=KEYS;
$hash{$_}=1 for 1 .. KEYS;

__END__

##</code><code>##

#!/usr/bin/perl

use strict;
use warnings;
use constant KEYS => 10_000_000;

my %hash;
keys %hash=KEYS;
@hash{1..KEYS}=(1) x KEYS;

__END__