Dear monks,

perlretut states:
The answer to requirement 2), as of 5.6.0, is that if a regexp contains Unicode characters, the string is searched as a sequence of Unicode characters. Otherwise, the string is searched as a sequence of bytes.
However, in Unicode, some character may be represented in more than one way, e.g. as a single code point, or as a combined character.
I assumed (probably wrongly) that in a regular expresion, perl would know a combined character to be "one" character. But it doesn't look like it: 
#!/usr/bin/perl

my @t = ("A\x{300}B",       # U+0300 GRAVE ACCENT
         "AA",
         "A\x{41}\x{300}",  # U+0041 LATIN CAPITAL LETTER A
         "\x{55}\x{308}O",  # U+0308 COMBINING DIAERESIS 
         "\x{dc}U"          # U+00DC capital U with DIAERESIS
);

binmode(STDOUT, ':utf8');

for (@t) {
  print "MATCH: $_\n" if /\p{Lu}{2}/;
}

[download]

Uppercase characters represented by a single code point match. Combined characters match only if the combining mark isn't between the two characters. This is why
"A\x{300}B" doesn't match but "A\x{41}\x{300}" matches.

My question: is it possible to write regular expressions so that combined characters are treated as "single" characters by the regular expression engine?

Any help would be very appreciated.

In reply to unicode combined characters in regular expressions by telcontar

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