Wrapping the code in eval only makes sense if you ask decode to die if it can't decode:

eval {
    $unicode = Encode::decode($from,$str,Encode::FB_CROAK);
};
if ($@)
{
    &ConvertEncodingError("($from -> utf8)\n$@");
    return $str;
}
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You should be aware that in case of a decoding error, $str will be overwritten.