{with {x 3}
{with {f {fun {y} {+ x y}}}
{with {x 5}
{call f 4}}}} []
{with {f {fun {y} {+ x y}}}
{with {x 5}
{call f 4}}} [(x,3)]
{with {x 5} {call f 4}} [(f,{fun {y} {+ x y}}), (x,3)]
{call f 4} [(x,5),(f,{fun {y} {+ x y}}),(x,3)]
{+ x y} [(y,4),(x,5),(f,{fun {y} {+ x y}}),(x,3)]
----------------------------------------------------------------------
{call {with {x 3} {fun {y} {+ x y }}} 4} []
> {with {x 3} {fun {y} {+ x y}}} []
> {fun {y} {+ x y}} [(x,3)]
=> {fun {y} {+ x y}}
{call {fun {y} {+ x y}} 4}