A few questions about ISWIM
The wikipedia page for ISWIM says that it is a higher-order language, and that ISWIM is syntactic sugar for the $\lambda$-calculus. 

Although it seems to have no explicit $\lambda$ construct, thereby making it impossible to have anonymous functions, one achieves the same expressive power by combining lexical scoping and first-class functions: Define a new name  for a function locally; pass function as value to higher-order function.