You don't want a hash in that middle level, then, you want an array: $db_hash{$path}[$idx]{$key}. To do that, you'd do:

while (<>) {
  my ($path, $start, $end, $delay) = split;  # or however you get them
  push @{ $db_hash{$path} }, {
    START => $start,
    END => $end,
    DELAY => $delay,
  };
}
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