The manual entry for ereg is at:
http://www.php.net/manual/en/function.ereg.php
In it you'll notice that ereg requires at least two arguments. It looks like you've only made an attempt to provide the search pattern. Where is the string that it's supposed to use?
Also, if you are wanting to grab all the characters before the @ character, why not do exactly that? Perhaps something like:
ereg("(.)+@",$data,$regs)
$regs[1] should be whatever was found inside the parenthesis. Look at the examples in the manual.
Also, I think you're incorrectly using the { } characters. They are used to specify how many characters you want to match.
Here's a phpbuilder article on regular expressions.
http://www.phpbuilder.com/columns/dario19990616.php3