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@list = split('', $read);

...
    $key = sprintf("%s%2.2x", $key, $_);
    print $key, "\n";
}

@list = unpack 'C*', $read;

@list = split('', $read); 
$key = join "", map { sprintf "%2.2x", ord } @list;

@list = unpack 'C*', $read; 
$key = join "", map { sprintf "%2.2x", $_ } @list;