the "with-" pattern (originally from lisp, i believe, but ruby did a lot to bring it to the masses), where something like a filehandle manages its own lifecycle, and calls your closure in between. so rather than the C-like

    let f = open-file-for-writing(filename);  
    for line in array {  
      write-line-to-file(f, line);
    }
    close-file(f);

you can do

    with-open-file-for-writing(filename) {|f|
      for line in array {
        write-line-to-file(f, line);
      }
    }

where the definition of with-open-file-for-writing() would look like

    def with-open-file-for-writing(filename, closure) {
      let f = open-file-for-writing(filename);
      call-closure(closure, f);
      close-file(f);
    }

the benefit of having this be a closure rather than just a function pointer can be seen in the write array to file example above, where the "array" variable is in the scope of the calling function, but when with-open-file-for-writing calls your closure it can make full use of its own local variables.