%newHash = %$bigHash will suffice. I do not understand what you mean you do not have access to %bigHash in your example %bigHash simply does not exists: it exists an anonymous hash ie $bigHash

For the copy what you say is impossible:

perl -MData::Dumper -e '$href={a=>1,b=>{c=>1,d=>{e=>5}}}; %copy = %$hr
+ef; print Dumper \%copy'

$VAR1 = {
          'a' => 1,
          'b' => {
                   'c' => 1,
                   'd' => {
                            'e' => 5
                          }
                 }
        };
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L*