Is it possible to store arrays in a custom field?

Question

If I understand correctly, custom fields work like this:

key(string/int) => value(string/int)

Is it possible to define a custom field like this?

key(string/int) => value(array (string/int, string/int))

I want to use such a structure for storing a series of quotations in [quote, source] format, thinking that it would minimize potential input error compared with, say, str_splitting a single value.