add a more straightforward example for #1953

_examples/routing/dynamic-path/at-username/main.go

@@ -0,0 +1,30 @@
+package main
+
+import "github.com/kataras/iris/v12"
+
+func main() {
+	app := iris.New()
+
+	app.Get("/", func(c iris.Context) {
+		c.Writef("Hello %s", "world")
+	})
+
+	// This is an Iris-only feature across all web frameworks
+	// in every programming language for years.
+	// Dynamic Route Path Parameters Functions.
+	// Set min length characters to 2.
+	// Prefix of the username is '@'
+	// Otherwise 404.
+	//
+	// You can also use the regexp(...) function for more advanced expressions.
+	app.Get("/{username:string min(2) prefix(@)}", func(ctx iris.Context) {
+		username := ctx.Params().Get("username")[1:]
+		ctx.Writef("Username is %s", username)
+	})
+
+	// http://localhost:8080          -> FOUND (Hello world)
+	// http://localhost:8080/other    -> NOT FOUND
+	// http://localhost/@             -> NOT FOUND
+	// http://localhost:8080/@kataras -> FOUND (username is kataras)
+	app.Listen(":8080")
+}