I'm trying to get my head around some Unicode issues:

I want to compare text strings at the grapheme level, and I thought that the way to do it is to use one of the normalization form provided by Unicode::Normalize.

I tried the four most common normalization forms, but different representations of the same grapheme (an "a" with two marking characters in different order) are never converted to the same form. 

#!/usr/bin/perl
use strict;
use warnings;
use charnames qw(:full);
use Unicode::Normalize qw(NFKD NFD NFKC NFC reorder);

my $str1 = "\N{LATIN SMALL LETTER A}\N{COMBINING ACUTE ACCENT}\N{COMBI
+NING GRAVE ACCENT}";
my $str2 = "\N{LATIN SMALL LETTER A}\N{COMBINING GRAVE ACCENT}\N{COMBI
+NING ACUTE ACCENT}";
binmode STDOUT, ':utf8';


print "success\n" if $str1 eq $str2;

print "NFKD:\n";
dump_charnames(NFKD($str1));
dump_charnames(NFKD($str2));
print "success\n" if NFKD($str1) eq NFKD($str2);

print "NFD:\n";
dump_charnames(NFD($str1));
dump_charnames(NFD($str2));
print "success\n" if NFD($str1) eq NFD($str2);

print "NFC:\n";
dump_charnames(NFC($str1));
dump_charnames(NFC($str2));
print "success\n" if NFC($str1) eq NFC($str2);

print "NFKC:\n";
dump_charnames(NFKC($str1));
dump_charnames(NFKC($str2));
print "success\n" if NFKC($str1) eq NFKC($str2);

print "reorder:\n";
dump_charnames(reorder($str1));
dump_charnames(reorder($str2));
print "success\n" if reorder($str1) eq reorder($str2);

sub dump_charnames {
    my $str = $_[0];
    print map { '\N{' . charnames::viacode(ord $_) . '}' }
            split m//, $str;
    print "\n";
}
__END__
\N{LATIN SMALL LETTER A}\N{COMBINING ACUTE ACCENT}\N{COMBINING GRAVE A
+CCENT}
\N{LATIN SMALL LETTER A}\N{COMBINING GRAVE ACCENT}\N{COMBINING ACUTE A
+CCENT}
NFD:
\N{LATIN SMALL LETTER A}\N{COMBINING ACUTE ACCENT}\N{COMBINING GRAVE A
+CCENT}
\N{LATIN SMALL LETTER A}\N{COMBINING GRAVE ACCENT}\N{COMBINING ACUTE A
+CCENT}
NFC:
\N{LATIN SMALL LETTER A WITH ACUTE}\N{COMBINING GRAVE ACCENT}
\N{LATIN SMALL LETTER A WITH GRAVE}\N{COMBINING ACUTE ACCENT}
NFKC:
\N{LATIN SMALL LETTER A WITH ACUTE}\N{COMBINING GRAVE ACCENT}
\N{LATIN SMALL LETTER A WITH GRAVE}\N{COMBINING ACUTE ACCENT}
reorder:
\N{LATIN SMALL LETTER A}\N{COMBINING ACUTE ACCENT}\N{COMBINING GRAVE A
+CCENT}
\N{LATIN SMALL LETTER A}\N{COMBINING GRAVE ACCENT}\N{COMBINING ACUTE A
+CCENT}

[download]

What am I doing wrong, and how can I transform the strings to a canonical form that is fit for comparison?

Or is it just this weird grapheme which doesn't occur "in the wild" and causes problems?

In reply to Comparing strings at grapheme level by moritz

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