my $valid_XML_BaseChars =
    join('',
         "\x{0041}-\x{005A}",    # Uppercase A-Z
         "\x{0100}-\x{0131}",    # Extended Latin A subset
                                 # Skipping ligatures 0132, 0133
         "\x{0134}-\x{013E}",    # Continuing Ext. Latin A
                                 # Skipping middle dots 013F, 0140
         "\x{0141}-\x{0148}",    # Finishing Ext. Latin A
         "\x{01FA}-\x{0217}",    # Extended Latin B subset
         "\x{0250}-\x{02A8}",    # IPA Extensions
        );
my $XML_BaseChar= qr/[$valid_xml_basechar]/o;