anchor.diff:    distfiles="http://www.foo.org/foo-${version}.tar.gz"
     checksum="fea0a94d4b605894f3e2d5572e3f96e4413bcad3a085aae7367c2cf07908b2ff"
     # end of source section
  -  
     # package section
     foo_package() {
       pkg_install() {
  
positive.code:     depend on additional packages.
  
  `perl-ModuleBuild`::
      For packages that use the Perl [Module::Build](http://search.cpan.org/~leont/Module-Build-0.4202/lib/Module/Build.pm) method.
  
  `perl`::
      For packages that use the standard Perl [ExtUtils::MakeMaker](http://perldoc.perl.org/ExtUtils/MakeMaker.html) build method.
  
  `python-module`::
      For packages that use the Python module build method (setup.py).
  
negative.code: `waf3`::
     For packages that use the Python3 `waf` build method with python3.
  
  `waf`::
     For packages that use the Python `waf` method with python2.
  
  source section - functions
  --------------------------
  
  The following functions can be defined to change the behavior of how the
  package is downloaded, compiled and installed.
  
  `do_fetch`::
      if defined and `distfiles` is not set, use it to fetch the required sources.
  