use HTML::Entities qw( decode_entities );

use locale qw();

my $lc = decode_entities('ä');
my $uc = decode_entities('Ä');

utf8::downgrade($uc);

for (0..2) {
   if ($_ == 0) {
      utf8::downgrade($lc);
      locale->unimport();
      print("Byte Semantics\n");
      print("--------------\n");
   }
   elsif ($_ == 1) {
      utf8::downgrade($lc);
      locale->import();
      print("Locale Semantics\n");
      print("----------------\n");
   }
   elsif ($_ == 2) {
      utf8::upgrade($lc);
      locale->unimport();
      print("Unicode Semantics\n");
      print("-----------------\n");
   }

   if ($lc =~ /^\Q$uc\E\z/) {
      print("case sensitive match\n");
   }
   elsif ($lc =~ /^\Q$uc\E\z/i) {
      print("case insensitive match\n");
   }
   else {
      print("no match\n");
   }

   if ($lc =~ /^[[:alpha:]]\z/) {
      print("[:alpha:]\n");
   } else {
      print("Not [:alpha:]\n");
   }

   if ($lc =~ /^[\p{IsAlpha}]\z/) {
      print("\\p{IsAlpha}\n");
   } else {
      print("Not \\p{IsAlpha}\n");
   }

   print("\n");
}

##</code><code>##

Byte Semantics
--------------
no match
Not [:alpha:]
\p{IsAlpha}

Locale Semantics
----------------
no match
Not [:alpha:]
\p{IsAlpha}

Unicode Semantics
-----------------
case insensitive match
[:alpha:]
\p{IsAlpha}