Regular expression to verify email address

$email = "test@ansoncheung.com";
if (preg_match('/^[^0-9][a-zA-Z0-9_]+([.][a-zA-Z0- 9_]+)*[@][a-zA-Z0-9_]+([.][a-zA-Z0-9_]+)*[.][a-zA-Z]{2,4}$ /',$email)) {
 echo "Your email is ok.";
} else {
 echo "Wrong email address format";
}

Regular expression, email