anchor.diff:      "--enable-function-subdirs"
       "--enable-maildir-support"
       "--enable-readnullcmd=pager"
  -    "--enable-pcre"
  -    "--enable-cap"
  -    "--enable-gdbm"
  +    (enFlag "pcre" (pcre != null) null)
  +    (enFlag "cap" (libcap != null) null)
  +    (enFlag "gdbm" (gdbm != null) null)
       "--enable-largefile"
       "--enable-multibyte"
  +    # TODO: musl libc support
       "--disable-libc-musl"
       "--enable-dynamic-nss"
  -    "--with-term-lib=ncursesw"
  +    (wtFlag "term-lib" (ncurses != null) "ncursesw")
       "--with-tcsetpgrp"
     ];
   
  
positive.code: 
  with {
    inherit (stdenv.lib)
      enFlag;
  };
  
  let
  
negative.code: 
    buildInputs = [
      coreutils
      gdbm
      ncurses
      pcre
    ] ++ optionals (!stdenv.cc.isGNU) [
      libiconv
    ];
  
    postInstall = ''
      mkdir -p $out/share
      tar xf ${documentation} -C $out/share
    '' +
    /* TODO: convert this to install a static file */ ''
      mkdir -p $out/etc
      cat > $out/etc/zprofile <<EOF
      if test -e /etc/NIXOS; then
        if test -r /etc/zprofile; then
  