//@ works a bit like borrowing does in the real world: If your friend borrows a book from you, your friend
//@ can have it and work on it (and you can't!) as long as the book is still borrowed. Your friend could
//@ even lend the book to someone else. Eventually however, your friend has to give the book back to you,
//@ works a bit like borrowing does in the real world: If your friend borrows a book from you, your friend
//@ can have it and work on it (and you can't!) as long as the book is still borrowed. Your friend could
//@ even lend the book to someone else. Eventually however, your friend has to give the book back to you,