sub guess_mode {
    my $class = shift;
    ( ref($_[0]) =~ /^IO|FileHandle/) ? 'handle' : 
    ( ref($_[0]) eq 'SCALAR' )        ? 'stringref' : 
    ( $_[0] =~ /^\w{3-6}\:/ )         ? 'uri' : 
    ( length($_[0]) > 1024 )          ? 'string' : 
                                        'path';
  }