>> x: context [ foo: [] ]
>> append x/foo 10
== [10]
>> ?? x
x: make object! [
    foo: [10]
]
>> y: make x []
>> ?? y
y: make object! [
    foo: [10]
]
>> append y/foo 20
== [10 20]
>> ?? y
y: make object! [
    foo: [10 20]
]
>> ?? x
x: make object! [
    foo: [10]
]
>> a: context [ foo: copy [] ]
>> append a/foo 30
== [30]
>> ?? a
a: make object! [
    foo: [30]
]
>> b: make a []
>> append b/foo 40
== [30 40]
>> ?? b
b: make object! [
    foo: [30 40]
]
>> ?? a
a: make object! [
    foo: [30]
]