Fellow Monks!
I need your help and I beg for forgiveness if I am incorrectly using certain terminology (I ask for your merciful correction and enlightenment if needed in the matter).
In a nutshell I am looking to determine/conduct a listing of keys in this particular array of hashes:

$data[0]->{"level"}=12.8;
[download]

where "level" is one known key and there are other possible ones not known and I wish to list them.
How do I do this? I am betting that it is a simple one-liner.
Thank you. As always your help and wisdom are both greatly appreciated!!