Makes it easy to build EDSLs.  Very often, in an EDSL you want your users to be able to use a language that&#x27;s <i>almost</i> like the host language, but has one or two key constructs redefined.<p>I&#x27;m not sure it&#x27;s the choice I would&#x27;ve made, but I can see it being very attractive for someone whose primary experience with programming is designing a programming language.  Back when I was interested in PL design in college, I was a big fan of this property in languages as well.