Ok. Two problems.

First of all, $test is already a reference, so you don't need to pass a reference to the reference to use_hash. If, for some reason, this is what you intended, you're going to need to dereference $ref twice in use_hash. Otherwise change

use_hash(\$test);
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to

use_hash($test);
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Secondly, assuming you've made the change above, change line 19 to:

%{$ref->hash1}->{'two'} = 'twosdata';
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If you haven't made the change above, you'll have to nest a dereference of $ref into this statement, like so:

%{$$ref->hash1}->{'two'} = 'twosdata';
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