As you can see the data was not retrieved, and the tree now has a new empty entry. Why can't I get the description and why is the tree being modified?

Because your pseudocode modified you tree. Compare to this

sub funky {
  #pseudocode
}
my $var = [ 1, 2, [ 3, 4] ];
use Data::Dumper;
warn Dumper($var);
funky($var);
warn Dumper($var);
__END__
$VAR1 = [
          1,
          2,
          [
            3,
            4
          ]
        ];
$VAR1 = [
          1,
          2,
          [
          ]
        ];
[download]

See how that happens? Maybe you wanna Clone your tree or just the part that's being modified before handing it to that pseudocode.

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