#!/usr/bin/perl

use strict;
use warnings;
# use 5.010;

use Benchmark qw/cmpthese :hireswallclock/;

{
    my @chr=('a'..'z', 'A'..'Z');

    sub genkeys {
        map {
            join '' => map $chr[rand @chr], (1) x (5 + rand 10);
        } 1..shift;
    }
}

my %hash=map {$_ => 1} genkeys 5000;
my @test=(keys %hash, genkeys 5000);

{
    $|++;
    local $\="\n";
    open my $fh, '>', '/dev/null' or die "Can't open /dev/null: $!\n";

    cmpthese -60 => {
        assign => sub () {
            for my $input (@test) {
                if (my $ans = $hash{$input}) {
                    print $fh "$input => $ans";
                }
            }
        },
        double => sub () {
            for my $input (@test) {
                if (exists $hash{$input}) {
                    print $fh $hash{$input};
                }
            }
        } };
}

__END__

##</code><code>##

kirk:~ [15:16:04]$ ./bm.pl
         Rate double assign
double 29.4/s     --    -1%
assign 29.7/s     1%     --