[lbshzjvb] Unlambda with lambda

Are there programs in programming language Unlambda which require exponential space to write because of its lack of certain constructs?

The webpage mentions that abstraction elimination of lambdas can cause exponential growth.

Similarly, we would very much like "let" bindings (even if not supporting recursion) for syntactic sugar and to make programs easier to understand.  We change the point from a deliberately obfuscated language to one merely based on unusual primitives but which otherwise tries to be helpful to the programmer.

Write a translator from single-backtick syntax to surrounding parentheses like Lisp.

Or, would the language be easier to understand if it written in postfix syntax (reverse Polish) like PostScript?  Currently it has no explicit notion of an expression stack like PostScript, but I suspect it has one implicitly.