diff --git a/Library/Homebrew/cli_parser.rb b/Library/Homebrew/cli_parser.rb
index 7d56d40089..c6eb823c30 100644
--- a/Library/Homebrew/cli_parser.rb
+++ b/Library/Homebrew/cli_parser.rb
@@ -10,13 +10,12 @@ module Homebrew
         instance_eval(&block)
       end
 
-      def switch(*names, description: nil)
+      def switch(*names, description: nil, env: nil)
         description = option_to_description(*names) if description.nil?
         @parser.on(*names, description) do
-          names.each do |name|
-            @parsed_args["#{option_to_name(name)}?"] = true
-          end
+          enable_switch(*names)
         end
+        enable_switch(*names) if !env.nil? && !ENV["HOMEBREW_#{env.to_s.upcase}"].nil?
       end
 
       def comma_array(name, description: nil)
@@ -50,6 +49,14 @@ module Homebrew
         @parser.parse!(cmdline_args)
         @parsed_args
       end
+
+      private
+
+      def enable_switch(*names)
+        names.each do |name|
+          @parsed_args["#{option_to_name(name)}?"] = true
+        end
+      end
     end
   end
 end
diff --git a/Library/Homebrew/dev-cmd/irb.rb b/Library/Homebrew/dev-cmd/irb.rb
index 700cbe0097..b27cb4ab80 100644
--- a/Library/Homebrew/dev-cmd/irb.rb
+++ b/Library/Homebrew/dev-cmd/irb.rb
@@ -5,6 +5,8 @@
 #:    If `--pry` is passed or HOMEBREW_PRY is set, pry will be
 #:    used instead of irb.
 
+require "cli_parser"
+
 class Symbol
   def f(*args)
     Formulary.factory(to_s, *args)
@@ -21,7 +23,12 @@ module Homebrew
   module_function
 
   def irb
-    if ARGV.include? "--examples"
+    args = Homebrew::CLI::Parser.new do
+      switch "--examples"
+      switch "--pry", env: :pry
+    end.parse
+
+    if args.examples?
       puts "'v8'.f # => instance of the v8 formula"
       puts ":hub.f.installed?"
       puts ":lua.f.methods - 1.methods"
@@ -29,7 +36,7 @@ module Homebrew
       return
     end
 
-    if ARGV.pry?
+    if args.pry?
       Homebrew.install_gem_setup_path! "pry"
       require "pry"
       Pry.config.prompt_name = "brew"
@@ -45,7 +52,7 @@ module Homebrew
 
     ohai "Interactive Homebrew Shell"
     puts "Example commands available with: brew irb --examples"
-    if ARGV.pry?
+    if args.pry?
       Pry.start
     else
       IRB.start
diff --git a/Library/Homebrew/extend/ARGV.rb b/Library/Homebrew/extend/ARGV.rb
index 8f8a63c7ef..0a66a0abe6 100644
--- a/Library/Homebrew/extend/ARGV.rb
+++ b/Library/Homebrew/extend/ARGV.rb
@@ -268,10 +268,6 @@ module HomebrewArgvExtension
     include? "--fetch-HEAD"
   end
 
-  def pry?
-    include?("--pry") || !ENV["HOMEBREW_PRY"].nil?
-  end
-
   # eg. `foo -ns -i --bar` has three switches, n, s and i
   def switch?(char)
     return false if char.length > 1
diff --git a/Library/Homebrew/test/cli_parser_spec.rb b/Library/Homebrew/test/cli_parser_spec.rb
index 2c2c7d9d93..fadb5cc881 100644
--- a/Library/Homebrew/test/cli_parser_spec.rb
+++ b/Library/Homebrew/test/cli_parser_spec.rb
@@ -6,6 +6,7 @@ describe Homebrew::CLI::Parser do
       described_class.new do
         switch "-v", "--verbose", description: "Flag for verbosity"
         switch "--more-verbose",  description: "Flag for higher verbosity"
+        switch "--pry", env: :pry
       end
     }
 
@@ -34,6 +35,12 @@ describe Homebrew::CLI::Parser do
     it "raises an exception when an invalid option is passed" do
       expect { parser.parse(["--random"]) }.to raise_error(OptionParser::InvalidOption, /--random/)
     end
+
+    it "maps environment var to an option" do
+      allow(ENV).to receive(:[]).with("HOMEBREW_PRY").and_return("1")
+      args = parser.parse([])
+      expect(args.pry?).to be true
+    end
   end
 
   describe "test long flag options" do