It's a very good point to make that when trying to work out character encoding problems, you need to know what your display method is doing, as well as what your program is doing. That's why hex dumps of output are so useful (sad, but true).

But it's also worthwhile to understand the "?" output a little better. When any unicode-aware process (whether a perl script, display terminal, browser rendering engine, database client, database server, or whatever) is trying to convert from unicode to some other encoding, the standard default behavior is to replace a unicode character with "?" in case the output encoding does not have a character that maps to the given unicode code point.

When you see "?" in your outputs where you expect to see other characters, the first thing to do is to identify the point in the processing or display where unicode data has been converted to some other encoding.

When data is going the other direction (from some known or assumed "other" encoding), and the conversion process (wherever it is) sees input bytes or byte pairs that are not defined in the mapping table for the given non-unicode character set, it will put one or more "\x{fffd}" (the unicode "replacement character") in place of the uninterpretable parts in its output unicode string.

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