What is this regex means? : <p>I found this regex as an email validation but i can't understand what is means, I tried to enter multiple forms of emails but they didn't work, I think there is a problem in this regex.</p>

<p><strong>^[A-Z0-9][A-Z0-9._%+-]{0,63}@(?:[A-Z0-9]{1,63}.){1,125}[A-Z]{2,63}$</strong></p>

<p>can anyone explain what is this regex means and give an example for it.</p>

<p>Thanks in advance.</p>
