It is necessary if an empty key i.e. '', is legal & expected, but no processing is to be done for it i.e. it has to be avoided when processing all keys.

It's not too dissimilar to:

foreach $key (sort grep $_, keys %{$obj->somehash}) {
    .
    .
    .
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Update:

Updated to reflect the actual logic - original only tested for empty string ... c/w true/false test as pointed out elsewhere by Fletch.