diff --git a/Library/Homebrew/cask/lib/hbc/cli.rb b/Library/Homebrew/cask/lib/hbc/cli.rb
index d1fb991084..1378176da7 100644
--- a/Library/Homebrew/cask/lib/hbc/cli.rb
+++ b/Library/Homebrew/cask/lib/hbc/cli.rb
@@ -187,10 +187,10 @@ class Hbc::CLI
       end
 
       opts.on("--binarydir=PATH") do
-        opoo <<-EOF.undent
+        opoo <<-EOS.undent
           Option --binarydir is obsolete!
           Homebrew-Cask now uses the same location as your Homebrew installation for executable links.
-        EOF
+        EOS
       end
 
       FLAGS.each do |flag, method|
@@ -246,11 +246,11 @@ class Hbc::CLI
     end
 
     def purpose
-      puts <<-PURPOSE.undent
+      puts <<-EOS.undent
         brew-cask provides a friendly homebrew-style CLI workflow for the
         administration of macOS applications distributed as binaries.
 
-      PURPOSE
+      EOS
     end
 
     def usage
diff --git a/Library/Homebrew/cask/lib/hbc/cli/uninstall.rb b/Library/Homebrew/cask/lib/hbc/cli/uninstall.rb
index cd98b6e616..ae15414b72 100644
--- a/Library/Homebrew/cask/lib/hbc/cli/uninstall.rb
+++ b/Library/Homebrew/cask/lib/hbc/cli/uninstall.rb
@@ -27,10 +27,10 @@ class Hbc::CLI::Uninstall < Hbc::CLI::Base
 
       single = versions.count == 1
 
-      puts <<-EOF.undent
+      puts <<-EOS.undent
         #{cask_token} #{versions.join(', ')} #{single ? 'is' : 'are'} still installed.
         Remove #{single ? 'it' : 'them all'} with `brew cask uninstall --force #{cask_token}`.
-      EOF
+      EOS
     end
   end
 
diff --git a/Library/Homebrew/cask/lib/hbc/container/air.rb b/Library/Homebrew/cask/lib/hbc/container/air.rb
index e82b677e9c..fc618db831 100644
--- a/Library/Homebrew/cask/lib/hbc/container/air.rb
+++ b/Library/Homebrew/cask/lib/hbc/container/air.rb
@@ -11,12 +11,12 @@ class Hbc::Container::Air < Hbc::Container::Base
 
   def self.installer_cmd
     return @installer_cmd ||= INSTALLER_PATHNAME if installer_exist?
-    raise Hbc::CaskError, <<-ERRMSG.undent
+    raise Hbc::CaskError, <<-EOS.undent
       Adobe AIR runtime not present, try installing it via
 
           brew cask install adobe-air
 
-    ERRMSG
+    EOS
   end
 
   def self.installer_exist?
diff --git a/Library/Homebrew/cask/lib/hbc/system_command.rb b/Library/Homebrew/cask/lib/hbc/system_command.rb
index 6fa8a901fa..bb8d91504e 100644
--- a/Library/Homebrew/cask/lib/hbc/system_command.rb
+++ b/Library/Homebrew/cask/lib/hbc/system_command.rb
@@ -150,17 +150,17 @@ class Hbc::SystemCommand::Result
     _warn_plist_garbage(command, Regexp.last_match[2])
     xml = Plist.parse_xml(output)
     unless xml.respond_to?(:keys) && !xml.keys.empty?
-      raise Hbc::CaskError, <<-ERRMSG
+      raise Hbc::CaskError, <<-EOS
 Empty result parsing plist output from command.
   command was:
   #{command.utf8_inspect}
   output we attempted to parse:
   #{output}
-      ERRMSG
+      EOS
     end
     xml
   rescue Plist::ParseError => e
-    raise Hbc::CaskError, <<-ERRMSG
+    raise Hbc::CaskError, <<-EOS
 Error parsing plist output from command.
   command was:
   #{command.utf8_inspect}
@@ -168,6 +168,6 @@ Error parsing plist output from command.
   #{e}
   output we attempted to parse:
   #{output}
-    ERRMSG
+    EOS
   end
 end
diff --git a/Library/Homebrew/cask/spec/cask/cli/cleanup_spec.rb b/Library/Homebrew/cask/spec/cask/cli/cleanup_spec.rb
index e77576ae32..5753834e0c 100644
--- a/Library/Homebrew/cask/spec/cask/cli/cleanup_spec.rb
+++ b/Library/Homebrew/cask/spec/cask/cli/cleanup_spec.rb
@@ -18,11 +18,11 @@ describe Hbc::CLI::Cleanup do
 
       expect {
         subject.cleanup!
-      }.to output(<<-OUTPUT.undent).to_stdout
+      }.to output(<<-EOS.undent).to_stdout
         ==> Removing cached downloads
         #{cached_download}
         ==> This operation has freed approximately #{disk_usage_readable(cleanup_size)} of disk space.
-      OUTPUT
+      EOS
 
       expect(cached_download.exist?).to eq(false)
     end
@@ -38,11 +38,11 @@ describe Hbc::CLI::Cleanup do
 
       expect {
         subject.cleanup!
-      }.to output(<<-OUTPUT.undent).to_stdout
+      }.to output(<<-EOS.undent).to_stdout
         ==> Removing cached downloads
         skipping: #{cached_download} is locked
         ==> This operation has freed approximately #{disk_usage_readable(cleanup_size)} of disk space.
-      OUTPUT
+      EOS
 
       expect(cached_download.exist?).to eq(true)
     end
@@ -56,10 +56,10 @@ describe Hbc::CLI::Cleanup do
 
         expect {
           subject.cleanup!
-        }.to output(<<-OUTPUT.undent).to_stdout
+        }.to output(<<-EOS.undent).to_stdout
           ==> Removing cached downloads older than 10 days old
           Nothing to do
-        OUTPUT
+        EOS
 
         expect(cached_download.exist?).to eq(true)
       end
diff --git a/Library/Homebrew/cask/test/cask/artifact/uninstall_test.rb b/Library/Homebrew/cask/test/cask/artifact/uninstall_test.rb
index 4d6c5df1b5..4ab2dc3d28 100644
--- a/Library/Homebrew/cask/test/cask/artifact/uninstall_test.rb
+++ b/Library/Homebrew/cask/test/cask/artifact/uninstall_test.rb
@@ -42,7 +42,7 @@ describe Hbc::Artifact::Uninstall do
       let(:launchctl_remove_cmd) { %w[/bin/launchctl remove my.fancy.package.service] }
       let(:unknown_response) { "launchctl list returned unknown response\n" }
       let(:service_info) {
-        <<-PLIST.undent
+        <<-EOS.undent
           {
                   "LimitLoadToSessionType" = "Aqua";
                   "Label" = "my.fancy.package.service";
@@ -53,7 +53,7 @@ describe Hbc::Artifact::Uninstall do
                           "argument";
                   );
           };
-        PLIST
+        EOS
       }
 
       describe "when launchctl job is owned by user" do
@@ -124,7 +124,7 @@ describe Hbc::Artifact::Uninstall do
         ]
       }
       let(:pkg_info_plist) {
-        <<-PLIST.undent
+        <<-EOS.undent
           <?xml version="1.0" encoding="UTF-8"?>
           <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
           <plist version="1.0">
@@ -135,7 +135,7 @@ describe Hbc::Artifact::Uninstall do
                   <string>/</string>
           </dict>
           </plist>
-        PLIST
+        EOS
       }
 
       it "can uninstall" do
diff --git a/Library/Homebrew/cask/test/cask/artifact/zap_test.rb b/Library/Homebrew/cask/test/cask/artifact/zap_test.rb
index 8ffa1c5e30..489299eca3 100644
--- a/Library/Homebrew/cask/test/cask/artifact/zap_test.rb
+++ b/Library/Homebrew/cask/test/cask/artifact/zap_test.rb
@@ -43,7 +43,7 @@ describe Hbc::Artifact::Zap do
       let(:launchctl_remove_cmd) { %w[/bin/launchctl remove my.fancy.package.service] }
       let(:unknown_response) { "launchctl list returned unknown response\n" }
       let(:service_info) {
-        <<-PLIST.undent
+        <<-EOS.undent
           {
                   "LimitLoadToSessionType" = "Aqua";
                   "Label" = "my.fancy.package.service";
@@ -54,7 +54,7 @@ describe Hbc::Artifact::Zap do
                           "argument";
                   );
           };
-        PLIST
+        EOS
       }
 
       describe "when launchctl job is owned by user" do
@@ -125,7 +125,7 @@ describe Hbc::Artifact::Zap do
         ]
       }
       let(:pkg_info_plist) {
-        <<-PLIST.undent
+        <<-EOS.undent
           <?xml version="1.0" encoding="UTF-8"?>
           <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
           <plist version="1.0">
@@ -136,7 +136,7 @@ describe Hbc::Artifact::Zap do
                   <string>/</string>
           </dict>
           </plist>
-        PLIST
+        EOS
       }
 
       it "can zap" do
diff --git a/Library/Homebrew/cask/test/cask/cli/cat_test.rb b/Library/Homebrew/cask/test/cask/cli/cat_test.rb
index f51fe4be09..df49efda07 100644
--- a/Library/Homebrew/cask/test/cask/cli/cat_test.rb
+++ b/Library/Homebrew/cask/test/cask/cli/cat_test.rb
@@ -3,7 +3,7 @@ require "test_helper"
 describe Hbc::CLI::Cat do
   describe "given a basic Cask" do
     before do
-      @expected_output = <<-CLIOUTPUT.undent
+      @expected_output = <<-EOS.undent
         test_cask 'basic-cask' do
           version '1.2.3'
           sha256 '8c62a2b791cf5f0da6066a0a4b6e85f62949cd60975da062df44adf887f4370b'
@@ -13,7 +13,7 @@ describe Hbc::CLI::Cat do
 
           app 'TestCask.app'
         end
-      CLIOUTPUT
+      EOS
     end
 
     it "displays the Cask file content about the specified Cask" do
diff --git a/Library/Homebrew/cask/test/cask/cli/create_test.rb b/Library/Homebrew/cask/test/cask/cli/create_test.rb
index 85d888cfae..cf3cf28a36 100644
--- a/Library/Homebrew/cask/test/cask/cli/create_test.rb
+++ b/Library/Homebrew/cask/test/cask/cli/create_test.rb
@@ -37,7 +37,7 @@ describe Hbc::CLI::Create do
   it "drops a template down for the specified Cask" do
     Hbc::CLI::Create.run("new-cask")
     template = File.read(Hbc.path("new-cask"))
-    template.must_equal <<-TEMPLATE.undent
+    template.must_equal <<-EOS.undent
       cask 'new-cask' do
         version ''
         sha256 ''
@@ -49,7 +49,7 @@ describe Hbc::CLI::Create do
 
         app ''
       end
-    TEMPLATE
+    EOS
   end
 
   it "throws away additional Cask arguments and uses the first" do
diff --git a/Library/Homebrew/cask/test/cask/cli/search_test.rb b/Library/Homebrew/cask/test/cask/cli/search_test.rb
index a0365862ed..4b15d8eab8 100644
--- a/Library/Homebrew/cask/test/cask/cli/search_test.rb
+++ b/Library/Homebrew/cask/test/cask/cli/search_test.rb
@@ -4,11 +4,11 @@ describe Hbc::CLI::Search do
   it "lists the available Casks that match the search term" do
     lambda {
       Hbc::CLI::Search.run("photoshop")
-    }.must_output <<-OUTPUT.gsub(%r{^ *}, "")
+    }.must_output <<-EOS.undent
       ==> Partial matches
       adobe-photoshop-cc
       adobe-photoshop-lightroom
-    OUTPUT
+    EOS
   end
 
   it "shows that there are no Casks matching a search term that did not result in anything" do
diff --git a/Library/Homebrew/cask/test/cask/cli/uninstall_test.rb b/Library/Homebrew/cask/test/cask/cli/uninstall_test.rb
index e2909873a6..80d4576cd3 100644
--- a/Library/Homebrew/cask/test/cask/cli/uninstall_test.rb
+++ b/Library/Homebrew/cask/test/cask/cli/uninstall_test.rb
@@ -57,11 +57,11 @@ describe Hbc::CLI::Uninstall do
       timestamped_versions.each do |timestamped_version|
         caskroom_path.join(".metadata", *timestamped_version, "Casks").tap(&:mkpath)
                      .join("#{token}.rb").open("w") do |caskfile|
-                       caskfile.puts <<-EOF.undent
+                       caskfile.puts <<-EOS.undent
                          cask '#{token}' do
                            version '#{timestamped_version[0]}'
                          end
-                       EOF
+                       EOS
                      end
         caskroom_path.join(timestamped_version[0]).mkpath
       end
@@ -112,13 +112,13 @@ describe Hbc::CLI::Uninstall do
 
       saved_caskfile.dirname.mkpath
 
-      IO.write saved_caskfile, <<-EOF.undent
+      IO.write saved_caskfile, <<-EOS.undent
         cask 'ive-been-renamed' do
           version :latest
 
           app 'ive-been-renamed.app'
         end
-      EOF
+      EOS
     end
 
     after do
diff --git a/Library/Homebrew/cask/test/cask/dsl_test.rb b/Library/Homebrew/cask/test/cask/dsl_test.rb
index 4cd30d2414..ce57e0b078 100644
--- a/Library/Homebrew/cask/test/cask/dsl_test.rb
+++ b/Library/Homebrew/cask/test/cask/dsl_test.rb
@@ -20,7 +20,7 @@ describe Hbc::DSL do
     end
 
     it "prints a warning that it has encountered an unexpected method" do
-      expected = Regexp.compile(<<-EOREGEX.undent.lines.map(&:chomp).join(""))
+      expected = Regexp.compile(<<-EOS.undent.lines.map(&:chomp).join(""))
         (?m)
         Warning:
         .*
@@ -29,7 +29,7 @@ describe Hbc::DSL do
         brew update; brew cleanup; brew cask cleanup
         .*
         https://github.com/caskroom/homebrew-cask#reporting-bugs
-      EOREGEX
+      EOS
 
       TestHelper.must_output(self, attempt_unknown_method, expected)
     end
diff --git a/Library/Homebrew/cask/test/cask/url_checker_test.rb b/Library/Homebrew/cask/test/cask/url_checker_test.rb
index cb0e50d575..2dfed62d3e 100644
--- a/Library/Homebrew/cask/test/cask/url_checker_test.rb
+++ b/Library/Homebrew/cask/test/cask/url_checker_test.rb
@@ -11,13 +11,13 @@ describe Hbc::UrlChecker do
     end
 
     it "properly populates the response code and headers from an http response" do
-      TestHelper.fake_response_for(TestHelper.test_cask.url, <<-RESPONSE.gsub(%r{^ *}, ""))
+      TestHelper.fake_response_for(TestHelper.test_cask.url, <<-EOS.undent)
         HTTP/1.1 200 OK
         Content-Type: application/x-apple-diskimage
         ETag: "b4208f3e84967be4b078ecaa03fba941"
         Content-Length: 23726161
         Last-Modified: Sun, 12 Aug 2012 21:17:21 GMT
-      RESPONSE
+      EOS
 
       checker = Hbc::UrlChecker.new(TestHelper.test_cask, TestHelper.fake_fetcher)
       checker.run