alias template parameters - opCall caller! example breaks in Programming in D, page 530

[Nick Treleaven]

On Saturday, 23 August 2025 at 13:38:27 UTC, Nick Treleaven wrote:
> I'm not aware of any template function called `caller` - 
> perhaps it is defined in the book somewhere?

```d
void caller(alias func)() {
     write("calling: ");
     func();
}
```
https://dlang.org/book/templates_more.html#ix_More%20Templates.alias,%20template%20parameter