Split the boolean class into an outer module

perl/lib/Data/MessagePack/Boolean.pm

@@ -0,0 +1,14 @@
+package Data::MessagePack::Boolean;
+use strict;
+use overload
+    'bool' => sub { ${ $_[0] } },
+    '0+'   => sub { ${ $_[0] } },
+    '""'   => sub { ${ $_[0] } ? 'true' : 'false' },
+
+    fallback => 1,
+;
+
+our $true  = do { bless \(my $dummy = 1) };
+our $false = do { bless \(my $dummy = 0) };
+
+1;