protected override Variable Evaluate(ParsingScript script)
{
// 1. Get the name of the variable.
string varName = Utils.GetToken(script, Constants.NEXT_ARG_ARRAY);
Utils.CheckNotEmpty(script, varName, m_name);
// 2. Get the current value of the variable.
ParserFunction func = ParserFunction.GetFunction(varName, script);
Variable currentValue = func.GetValue(script);
// 3. Get the value to be added or appended.
Variable newValue = Utils.GetItem(script);
// 4. Take either the string part if it is defined,
// or the numerical part converted to a string otherwise.
string arg1 = currentValue.AsString();
string arg2 = newValue.AsString();
// 5. The variable becomes a string after adding a string to it.
newValue.Reset();
newValue.String = arg1 + arg2;
ParserFunction.AddGlobalOrLocalVariable(varName, new GetVarFunction(newValue));
return(newValue);
}