What does this error mean?

Why does it go away if I remove the :shared attribute from %things?

Does it constitute a bug that should be reported?

#! perl -slw
use strict;

package test;
use threads;
use threads::shared;

my %things : shared;

sub new {
    my( $class, $thing ) = @_;
    my $self = bless \$class, $class;
    $things{ $self } = $thing;
    return $self;
}

sub thing : lvalue {
    $things{ $_[ 0 ] };
}

sub DESTROY {
    delete $things{ $_[ 0 ] };
}

return 1 if caller;

package main;

my $test = test->new( '12345' );
print $test->thing;

$test->thing = 98765; ## Line 32
print $test->thing;

undef $test;
__END__
P:\test>perl test.pm
12345
Can't return a temporary from lvalue subroutine at test.pm line 32.
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