well, one of my first languages was Pascal, where you have to tell your subroutines whether they get their parameters by value or by reference. That possybly had made me more aware of this one.
Which means, when I use sort, I have to pause thinking about whether it modifies in-place (Python) or returns a sorted copy (Perl)...
copied by reference
is just plain wrong terminology. References are used to avoid
Don't even think
in such terms! That impedes yourself, and then no wonder you're puzzled... regardless in which language you program.