That could work. However, if you say

        $errorcode = eval {@results = $instance_ref->$command(@_)} ;
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you are evaluating @results in scalar context and assigning the result of that evaluation to $errorcode - which is not what your want. Just say e.g.

        @results = eval { $instance_ref->$command(@_)} ;
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and check $@ for errors, which gets set if your eval'ed code dies.