Something like this should work (untested):
declare
fun {Add I}
% define a local function which adds I to its argument
fun {Adder J}
J + I
end
in
% returns this new function
Adder
end
{Show {{Add 1} 2}} % should print 3
% or more verbose:
declare
Add1 = {Add 1}
{Show {Add1 2}}