How to easily convert the pack function from little endian to big endian

semiconPERL has asked for the wisdom of the Perl Monks concerning the following question:

hi masters of perl, is there a way to easily convert this code

    read EP, $in, 2;
    $rec_len = unpack ("S", $in);
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so that the output of $rec_len is the same for big endian and little endian machines?