#!/usr/bin/env perl

use strict;
use warnings;

use Benchmark 'cmpthese';
use List::Util 'pairmap';
use Data::Dump;

my %h = qw{mammal cat mollusc snail fish cat};

print "*** Check initial data\n";
dd \%h;

print "*** Check subs return the same value\n";
print "_for\n";
dd _for();
print "_map\n";
dd _map();
print "_pairmap\n";
dd _pairmap();

print "*** Benchmark\n";
cmpthese 0 => {
    for => \&_for,
    map => \&_map,
    pairmap => \&_pairmap,
};

sub _for {
    my $result = [];

    for my $key (keys %h) {
        next unless $h{$key} eq 'cat';
        push @$result, $h{$key}, $key;
    }

    return $result;
}

sub _map {
    my $result = [];

    @$result = map { $h{$_} eq 'cat' ? ($h{$_}, $_) : () } keys %h;

    return $result;
}

sub _pairmap {
    my $result = [];

    @$result = pairmap { $b eq 'cat' ? ($b, $a) : () } %h;

    return $result;
}