There are several other ways to achieve your objective - you could pass the array ref into a sub, and use a local alias to an arayref, as in

sub HandleTres{
  my $tresRef = shift;
  $tresref->[0]= "Something else";
}
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or, use a reference assignment in your mainline code:

  my $TresRef = $myHash{tres};
  $TresRef->[1] = "Tres punto uno";
[download]