Why:

  } else {
    $_ = $_;
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which does nothing, and why:

    my $newdata = [ shopping => \@item ];
    $_ = $newdata;
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when you could just:

    $_ = [ shopping => \@item ];
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or maybe even:

    $_ = [shopping => [map {[item => $_]} qw(bread butter beans)]];
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for the whole if block.