Doesn't de-referencing the arrayref @$numbers_ref do an implicit copy (and allocate more space in the process)? I'm not sure.

I imagine a counting loop version would be more space-efficient:
  sub sum {
     my ($numbers_ref) = @_;
     my $sum = 0;
     foreach my $i (0 .. $#{ $numbers_ref }) {
       $sum += $numbers_ref->[$i];
     }
     return $sum;
  }

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In reply to Re: Curious Perl Behavior... by repellent
in thread Curious Perl Behavior... by ack

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