The meaning of chr(160) shouldn't change between Latin-1 and UTF-8, despite the different representation as bytes. It is the same character, Latin-1 being a subset of Unicode.
Comment on Re^2: inconsistency in whitespace handling
Right, but my point was that 0xa0 isn't considered a space character for a plain vanilla ASCII scalar without the utf magic enabled (underneath Perl's calling isspace(3), which only considers the characters space, form-feed, newline, carriage return, horizontal tab, and vertical tab to be whitespace).