anchor.diff:  , enableLDAP ? false, openldap
   , enableMySQL ? false, mysql, zlib
   , enableAuthDovecot ? false, dovecot
  +, enablePAM ? false, pam
   }:
   
   stdenv.mkDerivation rec {
  
positive.code:       ${stdenv.lib.optionalString enableAuthDovecot ''
          s:^# \(AUTH_DOVECOT\)=.*:\1=yes:
        ''}
        #/^\s*#.*/d
        #/^\s*$/d
      ' < src/EDITME > Local/Makefile
  
negative.code:   buildInputs = [ coreutils db openssl perl pcre ]
      ++ stdenv.lib.optional enableLDAP openldap
      ++ stdenv.lib.optionals enableMySQL [ mysql zlib ]
      ++ stdenv.lib.optional enableAuthDovecot dovecot
      ++ stdenv.lib.optional enablePAM pam;
  
    preBuild = ''
      ${stdenv.lib.optionalString enableMySQL "PKG_CONFIG_PATH=$PKG_CONFIG_PATH:${mysql}/share/mysql/pkgconfig/"}
  