sub process {
  my $node = shift;
  if (my $reftype = ref($node)) {
    return process_array($node) if $reftype eq 'ARRAY';
    return process_hash($node) if $reftype eq 'HASH';
    die "invalid node type: $reftype";
  } else {
    return process_scalar($node);
  }
}

process({ 'a' => '1', 'b' => [ '2' ],  'c' => { 'd' => '3' } });