Given this bit of your code (note: indenting helps):

foreach my $img ( sort keys %images ) {
   foreach ( @{$images{$img}} ) {   # this is line 11
      ...
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and this bit of output from Data::Dumper:

'intra-d_1050044970' => {
                  'frags' => [
                              ....
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The problem is that your second "foreach" is treating the content of "$images{$img}" as a reference to an array, when it is actually a reference to a hash (and the first key of that hash, as shown by Dumper, is 'frags'). The code should have been:

foreach my $img ( keys %images ) {
   foreach my $typ ( keys %{$images{$img}} ) {
       ... # next layer -- content of $images{$img}{$typ} -- depends o
+n value of $typ:
       ... # 'frac' has AoAoH
       ... # others have just a hash
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Hope that helps.