This happened to me with an XML based rules engine I wrote. First I needed conditions, then I introduced variables, then loops, then if-then-else. When I needed

This happened to me with an XML based rules engine I wrote. First I needed conditions, then I introduced variables, then loops, then if-then-else. When I needed to handle errors, I realized that I just had invented something like BASIC in XML format. The interpreter was surprisingly short and concise mainly because XML ensured I didn't have to do the parsing. Switched to dynamically compiled C# eventually.