HTTP::Message/HTTP::Response/HTTP::Response, ->content should always encoded in bytes ( octets ie 8-bit)

$ perl -MHTTP::Message -e" $a = HTTP::Message->new; $a->content( chr(5
+00) )"
HTTP::Message content must be bytes at -e line 1

$ perl -e"print utf8::is_utf8( chr(500) )"
1
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It relies on utf8::downgrade to check

$success = utf8::downgrade($string[, FAIL_OK])
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Converts in-place the internal octet sequence in *UTF-X* to the equivalent octet sequence in the native encoding (Latin-1 or EBCDIC). *$string* already encoded as native 8 bit does no harm. Can be used to make sure that the UTF-8 flag is off, e.g. when you want to make sure that the substr() or length() function works with the usually faster byte algorithm.