benchmark hash element assignment and testing

compare.pl

use Benchmark ':all';

my @array = 1 .. 1000;

cmpthese(
    10000,
    {

        '%foo = map { $_ => 1 } @array' => sub {
            my %foo = map { $_ => 1 } @array;
        },
        '@foo{@array} = undef' => sub {
            my %foo;
            @foo{@array} = undef;
        },
        '@foo{@array} = (1) x @array' => sub {
            my %foo;
            @foo{@array} = (1) x @array;
        },
        '@foo{@array} = @array' => sub {
            my %foo;
            @foo{@array} = @array;
        },
    },
);

my %foo = (1) x @array;

cmpthese(
    100000,
    {
        'grep  { exists $foo{_} } @array' => sub {
            my @foo = grep  { exists $foo{_} } @array;
        },
        'grep  { $_ } @foo{@array}' => sub {
            my @foo = grep  { $_ } @foo{@array};
        },
    },
);