app.psgi

use strict;
use warnings;

use Redis;

my $password = '';
my $host = '';

sub random_image {
  my $redis = Redis->new(server => $host);
  $redis->auth($password);
  my $key = $redis->randomkey;
  my $len = $redis->llen($key);
  my $index = int(rand($len)) - 1;
  return $redis->lindex($key, $index);
}

sub {
  my $image = random_image;
  my $body = "<a href='/'><img src='$image'></a>";
  [200, ['Content-Type' => 'text/html', 'Content-Length' => length $body], [$body]]
}

Makefile.PL

#!/usr/bin/env perl
use ExtUtils::MakeMaker;

WriteMakefile(
  PREREQ_PM => {'AnyEvent::Feed' => '0.3'},
  PREREQ_PM => {'AnyEvent::Redis' => '0.23'},
  PREREQ_PM => {'Redis' => '1.904'},
);

update_images.pl

#!/usr/bin/perl

use strict;
use warnings;

use AnyEvent;
use AnyEvent::Feed;
use AnyEvent::Redis;

my $password = '';
my $host = '';
my $port = '';

my @feeds;
my $redis = AnyEvent::Redis->new(
  host => $host,
  port => $port,
);
my $img_re = qr{https?://[^\s]+\.(?:gif|png|jpe?g)}i;
my $cv = AE::cv;

sub add_feed {
  my $url = shift;

  my $feed = AnyEvent::Feed->new(url => $url);

  $cv->begin;
  $feed->fetch(sub {
    my ($reader, $new, $feed, $error) = @_;

    my @images = map {($_->content->body =~ /($img_re)/g)} $feed->entries;

    $redis->del($url, sub {});

    for my $image (@images) {
      $cv->begin;
      $redis->lpush($url, $image, sub {$cv->end});
    }

    $cv->end;
  });
  push @feeds, $feed;
}

$redis->auth($password, sub {});

add_feed 'http://cutegirlsbeingcute.tumblr.com/rss';
add_feed 'http://getoutoftherecat.tumblr.com/rss';
add_feed 'http://thisiswhyyourefat.tumblr.com/rss';

$cv->recv;