tangent pretty much covered this, but I can expand a little bit more about the arrayref bit:

Like tangent said, the hashref $seen{$key}->{col1_vals} points to is an arrayref. To sum its contents, you can do something like this:

my $sum = 0;
foreach (@{$seen{$key}->{col1_vals}}) {
    $sum += $_;
}

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In reply to Re^4: Hashes, Arrays, and Confusion -- In a bit over my head! by Riales
in thread Hashes, Arrays, and Confusion -- In a bit over my head! by bpthatsme

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