If the following works perfectly:
 
if(!eregi("^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2}|[com|net|org|edu|info])$", $email))
$errors[] = "A \"Valid e-Mail Address\" is required";
 
 
Then why doesnt the below work ??
 
if(!eregi("^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2}|[com|net|org|edu|info|ab.ca|on.ca|org.us|co.uk])$", $email))
$errors[] = "A \"Valid e-Mail Address\" is required";

Then when I try to further "escape" the periods it also doesn't work

if(!eregi("^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2}|[com|net|org|edu|info|ab\.ca|on\ca|org\.us|co\.uk])$", $email))
$errors[] = "A \"Valid e-Mail Address\" is required";