$ perl -le'print "\x{00A0}" =~ /\s(?<![ \n])/ ?1:0;'
0  # Expected

$ perl -E'say "\x{00A0}" =~ /\s(?<![ \n])/ ?1:0;'
0  # Feature unicode_strings doesn't fix regexes yet.

$ perl -le'print "\N{U+00A0}" =~ /\s(?<![ \n])/ ?1:0;'
1  # \N always returns an upgraded string.

$ perl -le'print "\x{2660}\x{00A0}" =~ /\s(?<![ \n])/ ?1:0;'
1  # Forces the use of an upgraded string.