in reply to How would I write this using map?

Using map, it would look like this: 
push @$ref2array, map $_, sort keys %{$obj->things};

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... which could then be distilled to: 
push @$ref2array, sort keys %{$obj->things};

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It's all fine and dandy until someone has to look at the code.

In Section Seekers of Perl Wisdom