A side note - really just a personal preference of mine that might help you. Name variables what they are - if a scalar is a reference to a hash, name it as such. For example, if you pass a reference to a 'user' hash in to subroutine print_user, then do it this way:

   sub print_user {
      my $user_hashref = shift;
      print "user name = $user_hashref->{'name'}\n";
      print "user age  = $user_hashref->{'age'}\n";
   }

   ### main part of code ###
   my %user = { "name" => "John Doe",
                "age"  => 12 }
   print_user(\%user);
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That way, you always know that scalar $user_hashref is really just a *reference* to the user hash, and it needs to be treated like a reference to a hash, instead of like an actual hash.

HTH.