You don't need to dereference the hash ref into a standard hash variable to use it. As the previous poster said, this will make a copy of the hash instead of editing the original. You can use a hash ref just as you would a standard hash by dereferencing as needed. Below are comparisons of some common hash syntax.
Hash Hash Ref
my %hash = (key=>'value'); my $hash_ref = {key=>'value'};
$hash{key} = 'mod_value'; $hash_ref->{key} = 'mod_value';
print $hash{key}; print $hash_ref->{key};
my @keys = keys %hash; my @keys = keys %{$hash_ref};
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