Find all letters in a list

default
{
    touch_start(integer total_number)
    {
        list data = ["A","B","C","D","A"];
		integer index;
		list positions=[];
		string letterToFind = "A";

		while (index<llGetListLength(data)){
			if (llList2String(data,index)==letterToFind){
				positions+=index;
			}
			index++;
		}
		llOwnerSay("Positions: " + llList2CSV(positions));
    }
}