I need help on validating email entries

[xux]

Hi everybody,
                I want to check whether email entries are entered properly.pls my regex expresion  have been saying not valid even when i entered my email addy.The regex am using is"if(!eregi ('^[a-zA-Z0-9_\-\.]+@[a-zA-Z0-9\-]+\.[a-zA-Z0-9\-\.]+$',$email))
{
  echo'That is not a valid email address.';
  exit;
}
"
Please I need help.Thanks