The lower level layers 'know', and will emit a warning if they detect chars > 255 on a stream NOT marked as UTF8, AND will not encode chars between 128 - 255, as UTF8 unless the stream was previously marked as UTF8.

The lower level always expects bytes. (Files are blocks/streams of bytes.) It will ALWAYS emit a warning if it detects chars >255.

In reply to Re^3: How to tell if a stream is already in UTF8 mode? by ikegami
in thread How to tell if a stream is already in UTF8 mode? by perl-diddler

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