What's wrong with my code preg_match

What's wrong with my code preg_match

if(!preg_match("^[_a-z0-9-]+(.[_a-z0-9-]+)@[a-z0-9-]+(.[a-z0-9-]+)(.[a-z]{2,3})$",
$email)){
Warning: preg_match(): No ending delimiter '^' found in
C:\xampp\htdocs\Test\source\index.php on line 28