ActionScript 3.0 :: Flash Escape Regular Expressions Characters?

I am trying to find if a substring (pattern) is included in a string (path). I use the search method of String class, but if my pattern string includes regular expressions special characters (i.e. ()$), the search function returns (-1). How can I escape these characters?

Code:
// with path="hello$world" and pattern="hello$" this returns -1
function checkPath (pattern:String):int
{
var reg:RegExp = new RegExp(pattern);
return path.search(reg);
}