Once you have:
- the ability to wrap some commands up in a larger context
- an escaping system

Then you have the layering problem, of working out how to escape the inner stuff in a way that won't be misinterpreted. Tcl has this problem. Most programming languages don't as they have a sharp distinction between string literals and everything else, and a high reliance on brackets to explicitly limit the scope you need to read to understand an action unit.