The following code is taken from a game engine and manipulates "keys" of the form (\w+\.)+\w+. Each word represents a hash level.

our %GameState; # The entire game context

# looks up a key (passed as the first param) and adds the value
# (if provided as second param). Returns a reference to the value
# list.
sub Entity {
  my ($key, $value) = @_;
  return undef if ! defined $key;
  my $hash = \%GameGlobals::GameState;
  my @keys = split /\./, $key;

  map {$_ = lc $_} @keys;
  while (@keys && defined $hash) {
    my $key = shift @keys;
    if (@keys) {
      $hash->{$key} = {} if ! exists $hash->{$key};
      $hash = $hash->{$key};
    } else {
      $hash->{$key} = [] if ! exists $hash->{$key};
      push @{$hash->{$key}}, $_[1] if defined $value;
      return \$hash->{$key};
    }
  }
}
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Another thing you can do is use concatenated keys rather than a multidimensional data structure. (I don't know how critical the hierarchical nature is to your problem solution) That is, instead of:

$data {$a}{$b}
$data {$a}{$b}{$c}
$data {$d}{$e}
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$data{join "\0", $a, $b}
$data{join "\0", $a, $b, $c}
$data{join "\0", $d, $e}
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for (keys %data) {
   # you could do something with $data{$_} directly,
   # or if you need access to the individual keys ...
   my @keys = split /\0/;
   # ...
}
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If the hash is not ragged, you simply know its dimensionality. If you somehow lose this information

sub hashfirst { $_[0]->{($_) = keys %{$_[0]}} }
sub shape {
  my $h = shift;
  my @s;
  for (;'HASH' ne ref $h; $h = hashfirst($h)) {
    push @s, scalar(keys %$h);
  }
  @s
}
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may help you remember. This feels like an X-Y question.