http://www.perlmonks.org?node_id=1096827


in reply to Why does Encode::Repair only correctly fix one of these two tandem characters?

$ldqm = encode 'UTF-8', decode 'Windows-1252', encode 'UTF-8', $ldqm; $ldqm => 201C encode 'UTF-8' => E2 80 9C decode 'Windows-1252' => 00E2 20AC 0153 encode 'UTF-8' => C3 A2 E2 82 AC C5 93
$rdqm = encode 'UTF-8', decode 'Windows-1252', encode 'UTF-8', $rdqm; $rdqm => 201D encode 'UTF-8' => E2 80 9D decode 'Windows-1252' => 00E2 20AC ???? [error handling] => 00E2 20AC FFFD encode 'UTF-8' => C3 A2 E2 82 AC EF BF BD

Windows-1252 doesn't have a character defined for 9D, so when you decode('Windows-1252', "\x9D"), you do something irreversible. The following all result in C3 A2 E2 82 AC EF BF BD.