The following solution
http://static.rust-lang.org/doc/master/intro.html#owning-concurrency
is partially a good start...
but I believe it would be better to let the (D) compiler
optimization stage figure out _automatically_ if it needs to make
a copy of the variable `numbers` or not depending on whether
`numbers` is used or not further down the body of `main`.
Are there currently any semantic passes in DMD that checks where
reference data are read/written that could be utilized here?
Also Walter has talked about loads of data flow optimizations
pending in DMD that for example automatically make new
expressions immutable (and in turn shareable without locks) when
possible.
