Sorry, it was a mistake of my code.

For HoHoH solution, if I use my own dump routine instead of Dumper:

foreach $path ( keys %db_hash ) {
    print "List for $path...\n";
    foreach $index ( keys %{ $db_hash{$path} } ) {
        print "END: ", $db_hash{$path}{$index}{END}, "\n";
    }
 }
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then following comes to stdout:

Use of uninitialized value in print at ./utk.pl line 66, <FH> line 246
+99.
Use of uninitialized value in print at ./utk.pl line 66, <FH> line 246
+99.
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line 66 is the line of "print END" routine. In this case,

$db_hash{$path}{$index}{END}
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tries to access

$db_hash{$path}{'index'}{END}
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... which does not exist anyway. It was a mistake that I did not use the Dumper.