I ran into the exact same problem when trying to solve some (not very complicated in retrospect) errors in a body of text. Shallow copying a string that I was applying permutations to and storing in an array meant that every single string in the array was the same, so I could never have more than one permutation without pulling some hacks like this.

I would be very interested in a cleaner variant on the marshal load hack for non-primitives, or even some interesting doc/writeup on how this works.