Your problem is in the last line of the _read() method: 
return \%data;
this returns a reference to the GLOBAL %FileHash::data that is set by the do $file, so you are using the same hash for all FileHash objects.

The quickest way to solve this is to change the offending line with: 

return {%data};
which returns a reference to a COPY of %data, leaving %FileHash::data free to be clobbered by a new do $file

anyway, this will still leave your race conditions intact :-)

Joost.

In reply to Referencing globals clobbers data by Joost
in thread Tie-ing hashes clobbers data by Dave05

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