@Override
    public boolean onExecute() {
        String result = getArg().getResult().getString();

        if (result.startsWith("Re: ") || result.startsWith("RE: ") || result.startsWith("Fw: ") ||
            result.startsWith("FW: "))
        {
            result = result.substring(4);
        } else if (result.startsWith("Fwd: ")) {
            result = result.substring(5);
        }

        ((StringResultNode)getResult()).setValue(result);
        return true;
    }
Constructs an instance of this class with given argument.

@param arg The argument for this function.
searchlib/src/main/java/com/yahoo/searchlib/expression/NormalizeSubjectFunctionNode.java