use DecodedMsg;
tie $! , "DecodedMsg";

##</code><code>##

use strict; use warnings;
use Encode qw(decode encode);

sub show{
	printf "is_utf8=%d, len=%d, msg=%s\n", utf8::is_utf8($_), length($_), $_; 
}

#byte string utf8 hiragana
my $byte_error_msg=encode('UTF-8', join('', map{pack('U',$_)} 0x3042 .. 0x3052));

print "#test1: with byets\n";
$_ = $byte_error_msg ; 
show;

print "#test2: with decoded char\n";
$_ = decode("UTF-8", $byte_error_msg);
show;

print "#test3 with tied variable ... seems working\n";
{package DecodedMsg;
	use Encode qw(decode);
	sub TIESCALAR { 
		my $class=shift;
		print "class=$class\n";
		return bless( {} , $class );
	}
	sub STORE{ 
		my $self=shift;
		print "###in store arg=$_[0]\n";
		$self->{val}= $_[0];
	}	
	sub FETCH { 
		my $self=shift;
		if( utf8::is_utf8( $self->{val} ) ){
			return  $self->{val};
		} else {	
			print "#in fetch ... return decoded\n";
			return 	decode('UTF-8', $self->{val})
		}
	}
	1;
}

tie $_, "DecodedMsg";	#tie $_ to DecodedMsg
$_ = $byte_error_msg;
show;

print "#test4 with tied variable ... with system error\n";
tie $!, "DecodedMsg";
open(my $fh, "<", " /the/path/to/nowhere");
$_ =$!;
show;