mysolution.pl

$obj->{output}{plate}->@* =
    map { delete $_->{pi} if $_->{pi} eq ''; $_ }
    sort { $a->{i7} cmp $b->{i7} }
    sort { $a->{i5} cmp $b->{i5} }
    sort { $a->{pi} cmp $b->{pi} }

    grep {
    state $hash = {};
    my $obj;
    $obj->{pi} = $_->{pi} if $_->{pi};
    $obj->{i7} = $_->{i7};
    $obj->{i5} = $_->{i5};
    my $key = $json->encode($obj);
    $hash->{$key}++;
    $hash->{$key}>1?0:1;
    }
    sort { length $json->encode($b) <=> length $json->encode($a) }
    map { $_->{pi} = $_->{pi} || ''; $_ }

    $obj->{output}{plate}->@*;

say $json->encode( $obj->{output}{plate} );