Convert camel case to human readable string?

Is there a reg exp or function that will convert camel case, css and underscore to human readable format? It does not need to support non-humans at this time. Sorry aliens. :(

Examples:

helloWorld -> "Hello World"
hello-world -> "Hello World"
hello_world -> "Hello World"

Here is the ActionScript version based on the idea from Ricks C example code. For JavaScript version remove the strong typing. For example, change var value:String to var value. Basically remove any declaration that starts with a semicolon, :String, :int, etc.

/**
 * Changes camel case to a human readable format. So helloWorld, hello-world and hello_world becomes "Hello World". 
 * */
public static function prettifyCamelCase(value:String=""):String {
    var output:String = "";
    var len:int = value.length;
    var char:String;

    for (var i:int;i<len;i++) {
        char = value.charAt(i);

        if (i==0) {
            output += char.toUpperCase();
        }
        else if (char !== char.toLowerCase() && char === char.toUpperCase()) {
            output += " " + char;
        }
        else if (char == "-" || char == "_") {
            output += " ";
        }
        else {
            output += char;
        }
    }

    return output;
}

JavaScript version:

/**
 * Changes camel case to a human readable format. So helloWorld, hello-world and hello_world becomes "Hello World". 
 * */
function prettifyCamelCase(str) {
    var output = "";
    var len = str.length;
    var char;

    for (var i=0 ; i<len ; i++) {
        char = str.charAt(i);

        if (i==0) {
            output += char.toUpperCase();
        }
        else if (char !== char.toLowerCase() && char === char.toUpperCase()) {
            output += " " + char;
        }
        else if (char == "-" || char == "_") {
            output += " ";
        }
        else {
            output += char;
        }
    }

    return output;
}