Custom Code - Prevent subsequent processing

I have the following code which runs as Custom Code when the form is submitted. The idea is that it loops through all of the fields (assuming it's not an email field) and runs a regexp against the fields for a URL or Email address.

I'm still seeing some forms with URLs in the fields come through.

The last one I had was:
http://www.rmtbear.com/info-3.html

Validating the regexp at http://regexpal.com/ I get a match using:

(https?:\/\/)?([\da-z\.-]+)\.([a-z\.]{2,6})([\/\w \.-]*)*\/?

Can you see why this doesn't stop the form running?

The custom code is run as Controller and is the first OnSubmit event:

<?php
$isthisspam = false;
//Honeypot
if ( $form->data['parmaham'] != '' ) {
  $isthisspam=true;
}
foreach($form->data as $name => $value) {
    if ($name == 'email') {
	//Skip validation
	} else {
		//Email
		if (preg_match("/^([a-z0-9_\.-]+)@([\da-z\.-]+)\.([a-z\.]{2,6})$/",$value)) {
			$isthisspam=true;
		}
		//URL
		if (preg_match("/^(https?:\/\/)?([\da-z\.-]+)\.([a-z\.]{2,6})([\/\w \.-]*)*\/?$/",$value)) {
			$isthisspam=true;
		}
	}

    
}


//Is this spam?
if ($isthisspam) {
	$mainframe->redirect('http://www.ic3.gov/default.aspx');
}
?>

Do I need to exit() after the redirect to make sure?

Ah of course.

Thanks Bob

Have a good weekend.

Pete