$ ./redis-audit.rb
./redis-audit.rb:24:in `require': no such file to load -- redis (LoadError)
	from ./redis-audit.rb:24

$ which ruby -a
/usr/bin/ruby

$gem list -d

*** LOCAL GEMS ***

bundler (1.11.2)
    Authors: André Arko, Terence Lee, Carl Lerche, Yehuda Katz
    Homepage: http://bundler.io
    License: MIT
    Installed at: /var/lib/gems/1.8

    The best way to manage your application's dependencies

hiredis (0.6.1, 0.6.0)
    Author: Pieter Noordhuis
    Homepage: http://github.com/redis/hiredis-rb
    License: BSD-3-Clause
    Installed at (0.6.1): /var/lib/gems/1.8
                 (0.6.0): /var/lib/gems/1.8

    Ruby wrapper for hiredis (protocol serialization/deserialization and
    blocking I/O)

redis (3.2.2)
    Authors: Ezra Zygmuntowicz, Taylor Weibley, Matthew Clark, Brian
    McKinney, Salvatore Sanfilippo, Luca Guidi, Michel Martens, Damian
    Janowski, Pieter Noordhuis
    Homepage: https://github.com/redis/redis-rb
    License: MIT
    Installed at: /var/lib/gems/1.8

    A Ruby client library for Redis