diff --git a/lib/optimist.rb b/lib/optimist.rb
index d3f21da..ae3cfb8 100644
--- a/lib/optimist.rb
+++ b/lib/optimist.rb
@@ -175,8 +175,8 @@ def opt(name, desc = "", opts = {}, &b)
       @short[short] = o.name
     end
 
-    raise ArgumentError, "permitted values for option #{o.long.inspect} must be either nil or an array;" unless o.permitted.nil? or o.permitted.is_a? Array
-    
+    raise ArgumentError, "permitted values for option #{o.long.long.inspect} must be either nil, Range, Regexp or an Array;" unless o.permitted_type_valid?
+
     @specs[o.name] = o
     @order << [:opt, o.name]
   end
@@ -410,9 +410,11 @@ def parse(cmdline = ARGV)
         params << (opts.array_default? ? opts.default.clone : [opts.default])
       end
 
-      params[0].each do |p|
-        raise CommandlineError, "option '#{arg}' only accepts one of: #{opts.permitted.join(', ')}" unless opts.permitted.include? p
-      end unless opts.permitted.nil?
+      if params.first && opts.permitted
+        params.first.each do |val|
+          opts.validate_permitted(arg, val)
+        end
+      end
 
       vals["#{sym}_given".intern] = true # mark argument as specified on the commandline
 
@@ -730,7 +732,7 @@ def add(values)
 
 class Option
 
-  attr_accessor :name, :short, :long, :default, :permitted
+  attr_accessor :name, :short, :long, :default, :permitted, :permitted_response
   attr_writer :multi_given
 
   def initialize
@@ -741,6 +743,7 @@ def initialize
     @hidden = false
     @default = nil
     @permitted = nil
+    @permitted_response = "option '%{arg}' only accepts %{valid_string}"
     @optshash = Hash.new()
   end
 
@@ -796,32 +799,80 @@ def full_description
     desc_str
   end
 
+  ## Format stdio like objects to a string
+  def format_stdio(obj)
+    case obj
+    when $stdout   then '<stdout>'
+    when $stdin    then '<stdin>'
+    when $stderr   then '<stderr>'
+    else obj # pass-through-case
+    end
+  end
+
   ## Generate the default value string for the educate line
   private def default_description_str str
     default_s = case default
-                when $stdout   then '<stdout>'
-                when $stdin    then '<stdin>'
-                when $stderr   then '<stderr>'
                 when Array
                   default.join(', ')
                 else
-                  default.to_s
+                  format_stdio(default).to_s
                 end
     defword = str.end_with?('.') ? 'Default' : 'default'
     " (#{defword}: #{default_s})"
   end
 
+  def permitted_valid_string
+    case permitted
+    when Array
+      return "one of: " + permitted.to_a.map(&:to_s).join(', ')
+    when Range
+      return "value in range of: #{permitted}"
+    when Regexp
+      return "value matching: #{permitted.inspect}"
+    end
+    raise NotImplementedError, "invalid branch"
+  end
+
+  def permitted_type_valid?
+    case permitted
+    when NilClass, Array, Range, Regexp then true
+    else false
+    end
+  end
+
+  def validate_permitted(arg, value)
+    return true if permitted.nil?
+    unless permitted_value?(value)
+      format_hash = {arg: arg, given: value, value: value, valid_string: permitted_valid_string(), permitted: permitted }
+      raise CommandlineError, permitted_response % format_hash
+    end
+    true
+  end
+  
+  # incoming values from the command-line should be strings, so we should
+  # stringify any permitted types as the basis of comparison.
+  def permitted_value?(val)
+    case permitted
+    when nil then true
+    when Regexp then val.match permitted
+    when Range then permitted.to_a.map(&:to_s).include? val
+    when Array then permitted.map(&:to_s).include? val
+    else false
+    end
+  end
+
   ## Generate the permitted values string for the educate line
   private def permitted_description_str str
-    permitted_s = permitted.map do |p|
-      case p
-      when $stdout   then '<stdout>'
-      when $stdin    then '<stdin>'
-      when $stderr   then '<stderr>'
-      else
-        p.to_s
-      end
-    end.join(', ')
+    permitted_s = case permitted
+                  when Array
+                    permitted.map do |p|
+                      format_stdio(p).to_s
+                    end.join(', ')
+                  when Range, Regexp
+                    permitted.inspect
+                  else
+                    raise NotImplementedError
+                  end
     permword = str.end_with?('.') ? 'Permitted' : 'permitted'
     " (#{permword}: #{permitted_s})"
   end
@@ -868,6 +919,7 @@ def self.create(name, desc="", opts={}, settings={})
     ## autobox :default for :multi (multi-occurrence) arguments
     defvalue = [defvalue] if defvalue && multi_given && !defvalue.kind_of?(Array)
     opt_inst.permitted = permitted
+    opt_inst.permitted_response = opts[:permitted_response] if opts[:permitted_response]
     opt_inst.default = defvalue
     opt_inst.name = name
     opt_inst.opts = opts
diff --git a/test/optimist/parser_educate_test.rb b/test/optimist/parser_educate_test.rb
index 18185b1..b195268 100644
--- a/test/optimist/parser_educate_test.rb
+++ b/test/optimist/parser_educate_test.rb
@@ -169,6 +169,16 @@ def test_help_has_grammatical_permitted_text
     assert help[1] =~ /Permitted/
     assert help[2] =~ /permitted/
   end
+
+  def test_help_with_permitted_range
+    parser.opt :rating, 'rating', permitted: 1..5
+    parser.opt :hex, 'hexadecimal', permitted: /^[0-9a-f]/i
+    sio = StringIO.new 'w'
+    parser.educate sio
+    help = sio.string.split "\n"
+    assert_match %r{rating \(permitted: 1\.\.5\)}, help[1]
+    assert_match %r{hexadecimal \(permitted: \/\^\[0-9a-f\]\/i\)}, help[2]
+  end
 ############
 
     private
diff --git a/test/optimist/parser_permitted_test.rb b/test/optimist/parser_permitted_test.rb
new file mode 100644
index 0000000..42de4c8
--- /dev/null
+++ b/test/optimist/parser_permitted_test.rb
@@ -0,0 +1,93 @@
+require 'stringio'
+require 'test_helper'
+
+module Optimist
+
+class ParserPermittedTest < ::Minitest::Test
+  def setup
+    @p = Parser.new
+  end
+
+  def test_permitted_flags_filter_inputs
+    @p.opt "arg", "desc", :type => :strings, :permitted => %w(foo bar)
+
+    result = @p.parse(%w(--arg foo))
+    assert_equal ["foo"], result["arg"]
+    assert_raises(CommandlineError) { @p.parse(%w(--arg baz)) }
+  end
+
+  def test_permitted_invalid_scalar_value
+    err_regexp = /permitted values for option "(bad|mad|sad)" must be either nil, Range, Regexp or an Array/
+    assert_raises(ArgumentError, err_regexp) {
+      @p.opt 'bad', 'desc', :permitted => 1
+    }
+    assert_raises(ArgumentError, err_regexp) {
+      @p.opt 'mad', 'desc', :permitted => "A"
+    }
+    assert_raises_errmatch(ArgumentError, err_regexp) {
+      @p.opt 'sad', 'desc', :permitted => :abcd
+    }
+  end
+
+  def test_permitted_with_string_array
+    @p.opt 'fiz', 'desc', :type => 'string', :permitted => ['foo', 'bar']
+    @p.parse(%w(--fiz foo))
+    assert_raises_errmatch(CommandlineError, /option '--fiz' only accepts one of: foo, bar/) {
+      @p.parse(%w(--fiz buz))
+    }
+  end
+  def test_permitted_with_symbol_array
+    @p.opt 'fiz', 'desc', :type => 'string', :permitted => %i[dog cat]
+    @p.parse(%w(--fiz dog)) 
+    @p.parse(%w(--fiz cat)) 
+    assert_raises_errmatch(CommandlineError, /option '--fiz' only accepts one of: dog, cat/) {
+      @p.parse(%w(--fiz rat))
+    }
+  end
+
+  def test_permitted_with_numeric_array
+    @p.opt 'mynum', 'desc', :type => Integer, :permitted => [1,2,4]
+    @p.parse(%w(--mynum 1)) 
+    @p.parse(%w(--mynum 4)) 
+    assert_raises_errmatch(CommandlineError, /option '--mynum' only accepts one of: 1, 2, 4/) {
+      @p.parse(%w(--mynum 3))
+    }
+  end
+
+  def test_permitted_with_numeric_range
+    @p.opt 'fiz', 'desc', :type => Integer, :permitted => 1..3
+    opts = @p.parse(%w(--fiz 1))
+    assert_equal opts['fiz'], 1
+    opts = @p.parse(%w(--fiz 3))
+    assert_equal opts['fiz'], 3
+    assert_raises_errmatch(CommandlineError, /option '--fiz' only accepts value in range of: 1\.\.3/) {
+      @p.parse(%w(--fiz 4))
+    }
+  end
+
+  def test_permitted_with_regexp
+    @p.opt 'zipcode', 'desc', :type => String, :permitted => /^[0-9]{5}$/
+    @p.parse(%w(--zipcode 39762))
+    err_regexp = %r|option '--zipcode' only accepts value matching: /\^\[0-9\]\{5\}\$/|
+    assert_raises_errmatch(CommandlineError, err_regexp) {
+      @p.parse(%w(--zipcode A9A9AA))
+    }
+  end
+  def test_permitted_with_reason
+    # test all keys passed into the formatter for the permitted_response
+    @p.opt 'zipcode', 'desc', type: String, permitted: /^[0-9]{5}$/,
+           permitted_response: "opt %{arg} should be a zipcode but you have %{value}"
+    @p.opt :wig, 'wig', type: Integer, permitted: 1..4,
+           permitted_response: "opt %{arg} exceeded four wigs (%{valid_string}), %{permitted}, but you gave '%{given}'"
+    err_regexp = %r|opt --zipcode should be a zipcode but you have A9A9AA|
+    assert_raises_errmatch(CommandlineError, err_regexp) {
+      @p.parse(%w(--zipcode A9A9AA))
+    }
+    err_regexp = %r|opt --wig exceeded four wigs \(value in range of: 1\.\.4\), 1\.\.4, but you gave '5'|
+    assert_raises_errmatch(CommandlineError, err_regexp) {
+      @p.parse(%w(--wig 5))
+    }
+  end
+
+end
+end