You could use the same technique they used, but with the -=
operator.
>> a = []
=> []
>> a.object_id
=> 2154250660
>> a << 'hello'
=> ["hello"]
>> a.object_id
=> 2154250660
>> a += ['hi']
=> ["hello", "hi"]
>> a.object_id
=> 2154228260
>> a -= ['hi']
=> ["hello"]
>> a.object_id
=> 2154204700