Source code in the pop11 programming language

define hanoi(n, src, dst, via);
if n > 0 then
    hanoi(n - 1, src, via, dst);
    'Move disk ' >< n >< ' from ' >< src >< ' to ' >< dst >< '.' =>
    hanoi(n - 1, via, dst, src);
endif;
enddefine;

hanoi(4, "left", "middle", "right");