Magento 1.9 and PHP 5.6 – Deprecated Use of iconv.internal_encoding

I recommend you check your apache error log. You should make sure it isn't generating errors or you may very well get a blank screen.

The e modifier is short for eval. It performs a back reference substitution, then executes the replacement string as PHP, then performs the substitution using the returned value.

For example:

$pattern     = '/(.*)/e';
$replacement = 'strtoupper("$0");';
$input       = 'hello';
echo preg_replace($pattern, $replacement, $input);

Can be translated into:

$pattern     = '/(.*)/';
$input       = 'hello';
echo preg_replace_callback($pattern, function ($matches) {
    return strtoupper($matches[0]);
}, $input);

Without knowing what's returned by @file_get_contents($stylesheet) it's a little difficult to give accurate advice. The most obvious answer is the following, however be warned, this is pretty much as insecure as the e modifier (which is why it's deprecated):

echo preg_replace_callback('/\$([\w]+)/', function ($matches) {
    return eval($matches[0]);
}, $input);