The correct answer is JavaScript. This is because JavaScript is a client-side scripting language commonly used to create interactive effects within web browsers, including dynamic content updates, form validation, and animated graphics. Perl, although a versatile scripting language, is more traditionally used for systems administration, text processing, and web development on the server side rather than client-side interactions in a browser. PHP is a server-side scripting language used mainly for web development. Lastly, CSS is used for defining the presentation of a web document written in HTML or XML, but it does not provide interactive functionalities.