Hello GrandFather, thank you for your feedback and Wow, I never know param can do like that. I'm not quite understand what is $_[0] but I tested with it and it works well. 

sub doSub2 {
   # use name var instead of $_[0] so can easier to recall it
   my ($ref_value) = \$_[0];
   $$ref_value = "Hello alias";
}

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In reply to Re^4: Sub hash param by reference by hankcoder
in thread Sub hash param by reference by hankcoder

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