FFFD is a substitute for a character that could not be properly encoded. It is very unlikely that multiple encodings will produce useful results, but they could be useful for deliberately generating malformed output to feed to some other program that expects that type of malformed input.

I agree that pushing a second :encoding layer should produce a warning, though.

In reply to Re^5: using binmode() to override default encoding specified in "use open" by jcb
in thread using binmode() to override default encoding specified in "use open" by raygun

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