Even in a single-threaded environment, passing a struct around containing values allows you to implement dynamic scoping, which in this case means, you can easi

Even in a single-threaded environment, passing a struct around containing values allows you to implement dynamic scoping, which in this case means, you can easily call some functions with some overridden values in the global struct, and that code can also pass around modified versions of the struct, and so on, and it is all cleanly handled and scoped properly. This has many and sundry uses. If you just have a plain global variable this is much more difficult. Although Perl 5 has a nice feature where all global variables can automatically be treated this way by using a "local" keyword. It makes the global variables almost useful, and in my experience, makes people accidentally splattering globals around do a lot less damage than they otherwise would because they don't have to make explicit provision for scoped values. I don't miss many features from Perl but this is on the short list.