diff --git a/bin/penchant b/bin/penchant
index 30be87b..b6eecbe 100755
--- a/bin/penchant
+++ b/bin/penchant
@@ -2,8 +2,9 @@
 
 require 'rubygems'
 require 'thor'
+require 'penchant'
 
-class Penchant < Thor
+class PenchantCLI < Thor
   include Thor::Actions
   source_root File.expand_path('../..', __FILE__)
 
@@ -13,6 +14,11 @@ class Penchant < Thor
     directory 'template/script', options[:dir]
     Dir[File.join(options[:dir], '**/*')].each { |file| File.chmod(0755, file) }
   end
+
+  desc "gemfile ENV", "Switch the gemfile environment"
+  def gemfile(env)
+    Penchant::Gemfile.do_full_env_switch!(env)
+  end
 end
 
-Penchant.start
+PenchantCLI.start
diff --git a/lib/penchant/gemfile.rb b/lib/penchant/gemfile.rb
index eaad68c..ec640fd 100644
--- a/lib/penchant/gemfile.rb
+++ b/lib/penchant/gemfile.rb
@@ -1,8 +1,23 @@
+require 'erb'
+
 module Penchant
   class Gemfile
     attr_reader :path
 
-    def initialize(path)
+    class << self
+      def do_full_env_switch!(env)
+        gemfile = Penchant::Gemfile.new
+        if !gemfile.has_gemfile_erb?
+          puts "Not using Gemfile.erb, exiting."
+          return false
+        end
+
+        gemfile.switch_to!(env)
+        system %{bundle}
+      end
+    end
+
+    def initialize(path = Dir.pwd)
       @path = path
     end
 
@@ -26,10 +41,25 @@ module Penchant
       File.readlines(gemfile_path).first.strip[%r{environment: (.*)}, 1]
     end
 
+    def switch_to!(gemfile_env)
+      @env = gemfile_env
+      template = File.read(gemfile_erb_path)
+
+      File.open(gemfile_path, 'wb') do |fh|
+        fh.puts "# generated by penchant, environment: #{@env}"
+
+        fh.print ERB.new(template).result(binding)
+      end
+    end
+
     private
     def file_in_path(file)
       File.join(@path, file)
     end
+
+    def env(check, &block)
+      instance_eval(&block) if check.to_s == @env.to_s
+    end
   end
 end
 
diff --git a/spec/lib/penchant/gemfile_spec.rb b/spec/lib/penchant/gemfile_spec.rb
index c3bf923..1fcf153 100644
--- a/spec/lib/penchant/gemfile_spec.rb
+++ b/spec/lib/penchant/gemfile_spec.rb
@@ -49,15 +49,51 @@ GEMFILE
         its(:environment) { should == environment }
       end
     end
+
+    describe '#switch_to!' do
+      it 'should raise an exception' do
+        expect { subject.switch_to!(:whatever) }.to raise_error(Errno::ENOENT)
+      end
+    end
   end
 
   context 'with gemfile.erb' do
+    let(:erb_data) { 'whatever' }
+
     before do
-      write_file(gemfile_erb_path) { "whatever" }
+      write_file(gemfile_erb_path) { erb_data }
     end
 
     it { should_not have_gemfile }
     it { should have_gemfile_erb }
+
+    describe '#switch_to!' do
+      let(:erb_data) { <<-ERB }
+<% env :test do %>
+  test
+<% end %>
+
+<% env :not do %>
+  not
+<% end %>
+
+all
+ERB
+
+      it 'should render test data' do
+        subject.switch_to!(:test)
+
+        File.read('Gemfile').should include('test')
+        File.read('Gemfile').should include('all')
+      end
+
+      it 'should not render test data' do
+        subject.switch_to!(:not)
+
+        File.read('Gemfile').should include('not')
+        File.read('Gemfile').should include('all')
+      end
+    end
   end
 end
 
diff --git a/template/script/gemfile b/template/script/gemfile
index a067d07..eb78755 100755
--- a/template/script/gemfile
+++ b/template/script/gemfile
@@ -1,16 +1,11 @@
 #!/usr/bin/env ruby
 
-if !File.file?('Gemfile.erb')
-  puts "Not using Gemfile.erb, exiting."
+require 'rubygems'
+require 'penchant'
+
+if Penchant::Gemfile.do_full_env_switch!(ARGV[0])
+  puts "Gemfile switched to #{ARGV[0]}"
+else
   exit 0
 end
 
-require 'erb'
-
-env = ARGV[0]
-
-File.open('Gemfile', 'w') { |fh| fh.print ERB.new(File.read('Gemfile.erb')).result(binding) }
-system %{bundle}
-
-puts "Gemfile switched to #{env}"
-