# create a simple pair
var p = Pair('a', 'b')
say p.first;            #=> 'a'
say p.second;           #=> 'b'

# create a pair of pairs
var pair = 'foo':'bar':'baz':();   # => Pair('foo', Pair('bar', Pair('baz', nil)))

# iterate over the values of a pair of pairs
loop {
    say pair.first;                #=> 'foo', 'bar', 'baz'
    pair = pair.second;
    pair == nil && break;
}