anchor.diff:         => "/root/bin:/usr/bin:/usr/local/bin"
     */
     makeBinPath = pkgs: makeSearchPath "bin"
  -    (map (pkg: pkg.bin or (pkg.out or pkg)) pkgs);
  +    (map (pkg: if pkg.outputUnspecified or false then pkg.bin or (pkg.out or pkg) else pkg) pkgs);
   
   
     /* Construct a perl search path (such as $PERL5LIB)
  
positive.code:   */
    makeLibraryPath = pkgs: makeSearchPath "lib"
      # try to guess the right output of each pkg
      (map (pkg: pkg.lib or (pkg.out or pkg)) pkgs);
  
    /* Construct a binary search path (such as $PATH) containing the
       binaries for a set of packages.
  
negative.code:        => "/nix/store/n0m1fk9c960d8wlrs62sncnadygqqc6y-perl-Net-SMTP-1.25/lib/perl5/site_perl"
    */
    makePerlPath = pkgs: makeSearchPath "lib/perl5/site_perl"
      (map (pkg: if pkg.outputUnspecified or false then pkg.lib or (pkg.out or pkg) else pkg) pkgs);
  
    /* Dependening on the boolean `cond', return either the given string
       or the empty string. Useful to contatenate against a bigger string.
  