Fluid-Let

The syntax for a fluid-let expression is the same as for let:

  (fluid-let ((variable expr)   ) body-expr   ) 

Each variable must be either a local variable or a global variable that is bound before the fluid-let expression is evaluated. Before the body-exprs are evaluated, the bindings for the variables are set! to the values of the corresponding exprs. Once the body-exprs have been evaluated, the values of the variables are restored. The value of the entire fluid-let expression is the value of the last body-expr.