while ( ! eof ) {
    chunklen = 0;
    chunknum = 0;
    open( FOUT, ">chunk" . chunknum++ );
    # read into buffer, but at end of buffer in case of leftovers
    while ( len = read( FIN, buffer, 64000, length(buffer) ) ) {
      if ( chunklen + len > 400MB ) {
        # got to end of chunk, deal with newline
        lastnewline = rindex( buffer, "\n" );
        if ( lastnewline ) {
          # flush up to last found newline
          write( FOUT, substr( buffer, 0, lastnewline ) );
          substr( buffer, 0, lastnewline ) = "";
          close( FOUT );
          last; # skip to next file
        } else {
          # flush entire buffer (no newline found)
          write( FOUT, buffer );
          buffer = "";
        }
      } else {
        # not at end of chunk, just write buffer
        print( FOUT, buffer );
        buffer = "";
        chunklen += len;
      }
    } # while we've got something to read
  } # while not at eof of input