diff --git a/src/Cli/Program.elm b/src/Cli/Program.elm
index d73eb7e..1b23408 100644
--- a/src/Cli/Program.elm
+++ b/src/Cli/Program.elm
@@ -310,9 +310,11 @@ run (Config { optionsParsers }) argv versionMessage =
                 ++ (validationErrors
                         |> List.map
                             (\{ name, invalidReason } ->
-                                "`"
+                                "Invalid "
+                                    ++ "`--"
                                     ++ name
-                                    ++ "` failed a validation. "
+                                    ++ "` option."
+                                    ++ "\n"
                                     ++ invalidReason
                             )
                         |> String.join "\n"
diff --git a/src/Cli/Validate.elm b/src/Cli/Validate.elm
index 1d9a86b..e139fff 100644
--- a/src/Cli/Validate.elm
+++ b/src/Cli/Validate.elm
@@ -1,4 +1,4 @@
-module Cli.Validate exposing (predicate, ValidationResult(..), regex)
+module Cli.Validate exposing (predicate, ValidationResult(..), regex, regexWithExpectation)
 
 {-| This module contains helper functions for performing validations (see the
 "validate..." functions in `Cli.Option`).
@@ -83,3 +83,40 @@ regex regexPattern checkString =
 
             else
                 Invalid ("Must be of form /" ++ regexPattern ++ "/")
+
+{-| A helper for regex validations with an additional expectation message.
+
+    programConfig : Program.Config String
+    programConfig =
+        Program.config
+            |> Program.add
+                (OptionsParser.build identity
+                    |> OptionsParser.with
+                        (Option.requiredKeywordArg "name"
+                            |> Option.validate
+                                (Cli.Validate.regexWithExpectation "I expected this to be" "^[A-Z][A-Za-z_]*")
+                        )
+                )
+
+If the validation fails, the user gets output like this:
+
+```shell
+$ ./greet --name john
+Validation errors:
+
+`name` failed a validation. I expected this to be matching "^[A-Z][A-Za-z_]*" but got 'john'
+Value was:
+"john"
+```
+
+-}
+regexWithExpectation : String -> String -> String -> ValidationResult
+regexWithExpectation expectation regexPattern checkString =
+    case regex regexPattern checkString of
+        Valid ->
+            Valid
+
+        Invalid _ ->
+            Invalid (expectation ++ " matching \"" ++ regexPattern ++ "\", but got '" ++ checkString ++ "'")
+
+
diff --git a/tests/OptionsParserTests.elm b/tests/OptionsParserTests.elm
index f8177c7..00426fc 100644
--- a/tests/OptionsParserTests.elm
+++ b/tests/OptionsParserTests.elm
@@ -280,6 +280,32 @@ all =
                             |> OptionsParser.end
                         )
                         [ { name = "name", invalidReason = "Must be 3 characters long" } ]
+            , test "fails with expectation when regexWithExpectation validation function fails" <|
+                \() ->
+                    expectValidationErrors [ "--scalar-codecs", "src/ModuleName" ]
+                        (OptionsParser.build identity
+                            |> OptionsParser.with
+                                (Option.optionalKeywordArg "scalar-codecs"
+                                    |> Option.validateIfPresent
+                                        (\moduleName ->
+                                            Validate.regexWithExpectation "I expected an Elm module name" "^[A-Z][A-Za-z_]*(\\.[A-Z][A-Za-z_]*)*$" moduleName)
+                                )
+                            |> OptionsParser.end
+                        )
+                        [ { name = "scalar-codecs", invalidReason = "I expected an Elm module name matching \"^[A-Z][A-Za-z_]*(\\.[A-Z][A-Za-z_]*)*$\", but got 'src/ModuleName'" } ]
+            , test "succeeds when regexWithExpectation validation function passes" <|
+                \() ->
+                    expectMatch [ "--scalar-codecs", "ModuleName" ]
+                        (OptionsParser.build identity
+                            |> OptionsParser.with
+                                (Option.optionalKeywordArg "scalar-codecs"
+                                    |> Option.validateIfPresent
+                                        (\moduleName ->
+                                            Validate.regexWithExpectation "I expected an Elm module name" "^[A-Z][A-Za-z_]*(\\.[A-Z][A-Za-z_]*)*$" moduleName)
+                                )
+                            |> OptionsParser.end
+                        )
+                        (Just "ModuleName")
             , test "succeeds when validation function passes" <|
                 \() ->
                     expectMatch [ "--name", "Bob" ]