$me="me@my.domain";
$you="you@your.domain";
$subject="Easy question";
$message="Hey, this is in the manual. A cinch, really!";
$copy="Cc: $you\r\n";
mail($me, $subject, $message, $copy);
The fourth parameter is for "additional headers." Take a look at the
mail() manual page for more examples...
HTH,