> If there are regular expressions in the language syntax, or the library, it's a feature of the UTM. By "the library" do you mean the core library of the lang

> If there are regular expressions in the language syntax, or the library, it's a feature of the UTM. By "the library" do you mean the core library of the language? If a language didn't have regular expressions as part of its core library, does that mean regular expressions would not be a feature of that language? > Some features are simply not expressible in the target language of the rewriting, other than by using the syntax to create an inefficient, interpreted language. Why inefficient? Why interpreted? What if the syntax was efficiently compiled?