Like Algol and Pascal, and unlike most other dialects of Lisp
except for Common Lisp, the expression language is a statically scoped language with
block structure. To each place where a variable is bound in an expression
there corresponds a region of the expression text within which
the binding is effective. The region is determined by the particular
binding construct that establishes the binding; if the binding is
established by a lambda expression, for example, then its region
is the entire lambda expression. Every reference to, or assignment of,
a variable refers to the binding of the variable that established the
innermost of the regions containing the use. If there is no binding of
the variable whose region contains the use, then the use refers to the
binding for the variable in the top-level environment, if any;
if there is no binding for the identifier,
it is said to be unbound.