It just plain doesn't match anything! Looking at the module, I think it's a UTF-8 issue. E.g.

$Ideographic = '(?:\xE3\x80[\x87\xA1-\xA9]|\xE4(?:[\xB8-\xBF][\x80-\xB
+F])|\xE5(?:[\x80-\xBF][\x80-\xBF])|\xE6(?:[\x80-\xBF][\x80-\xBF])|\xE
+7(?:[\x80-\xBF][\x80-\xBF])|\xE8(?:[\x80-\xBF][\x80-\xBF])|\xE9(?:[\x
+80-\xBD][\x80-\xBF]|\xBE[\x80-\xA5]))';
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That is, \xE3 followed by \x80 \x87 are individual bytes in a UTF-8 encoded string, which won't match a real \x{2007} in the string.

However, my test data are normal ASCII range characters, and that doesn't succeed either, though it starts $BaseChar = '(?:[a-zA-Z]|\xC3[\x80-\x9.... So I don't know everything that's wrong with it, but it doesn't work at all (see below) if utf8 is used.

use strict;
use warnings;
use utf8;  # comment this line out and it matches
use XML::RegExp;

my $name= 'timestamp';  # contains plain ASCII letters only!
my $result= $name =~ /^$XML::RegExp::Name$/o;
print "result is $result\n";
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