anchor.diff:  
   with stdenv.lib;
   stdenv.mkDerivation rec {
  -  name = "znc-1.0";
  +  name = "znc-1.2";
  +
     src = fetchurl {
       url = "http://znc.in/releases/${name}.tar.gz";
  -    sha256 = "0ah6890ngvj97kah3x7fd8yzi6dpdgrxw1b2skj2cyv98bd3jmd8";
  +    sha256 = "07bh306wl5494sqsgz4a526wvyrylkc8vpnbr5pkxwjg90mcv8nr";
     };
   
     buildInputs = [ openssl pkgconfig ]
  
positive.code:     + optionalString withTcl "--enable-tcl --with-tcl=${tcl}/lib "
      + optionalString withCyrus "--enable-cyrus ";
  
    meta = {
      description = "Advanced IRC bouncer";
      homepage = http://wiki.znc.in/ZNC;
      maintainers = [ stdenv.lib.maintainers.viric ];
      license = "ASL2.0";
      platforms = stdenv.lib.platforms.unix;
    };
  }
  
negative.code: { stdenv, fetchurl, openssl, pkgconfig
  , withPerl ? false, perl
  , withPython ? false, python3
  , withTcl ? false, tcl
  