my $XML_BaseChar= qr/$_/ for join "",
   "[", # a character class...
   "\x{0041}-\x{005A}", # the first range
   "\x{0100}-\x{0131}\x{0134}-\x{013E}\x{0141}-\x{0148}", # the next range
   "\x{01FA}-\x{0217}\x{0250}-\x{02A8}", # etc.
   "]";  #here's how to close it up