In your hash definition 00 is interpolated numerically to become 0. What you need is:

$hash{'00'} = "data";
$hash{'10'} = "moredata";
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It's just "coincidence" that 10 = "10".

When you access the hash later, the key is interpolated in string context.

If you were doing 3 digits, things would be worse, because 010 = "8" (octal) and not "10".

Make sense?

cLive ;-)