ISWIM
If You See What I Mean.
Landin 1966.
ISWIM is purely functional, a sugaring of
lambda-calculus, and the ancestor of most modern applicative languages.
An ISWIM program is a single expression qualified by 'where' clauses (auxiliary definitions including equations among variables), conditional expressions and function definitions.
ISWIM was the first language to use
lazy evaluation and introduced the offside rule for indentation.
["The Next 700 Programming Languages", P.J. Landin, CACM 9(3):157-166