I'm trying to package Grue Hunter [1].

The game is just a single Perl file.  What directories should be created
in the store?  And how can I create such directories?

I've tried several things:

1. (zero? (system (format #f "cp -r . ~a" out)))

   Pollutes the profile with 'AGPLv3.txt', 'gh.pl', and 'README'.

2. (zero? (system (format #f "mkdir bin ~a/" out)))

   Creates 'bin', but the output doesn't contain it.

3. (zero? (system (format #f "mkdir bin ~a/" out)))
   (zero? (system (format #f "cp gh.pl ~a/bin/" out)))

   Creates a file called 'bin', not a directory.  Could anyone explain
   why?  Fails with:

   cp: cannot create regular file '/nix/store/clwpaljwanw7397qafxv82vj1b8jm82q-grue-hunter-1.0/bin/': Not a directory

I'm attaching a recipe and a related patch.

[1] http://jxself.org/grue-hunter.shtml