[davidgerard]

The temptation to do this in proprietaryware is strong because then your customers can customise their stuff without you giving away your precioussss.

Of course, then you have to support the terrible, terrible programming language you have just invented by accidentally making your DSL Turing complete.

Examples: ant, MediaWiki parser functions, whatever that thing Varnish uses is ... the Varnish one is less terrible than most Turing-complete configuration languages, but it still turns trying to read a config into trying to read source code. You don't want to do that to your future self.

(I have had to write actual code in Ant. It's as if COBOL were written in XML. Unbelievably horrible.)