This may be of interest... it's source from the Semaphore.pm:

sub new {
    my $class = shift;
    my $val : shared = @_ ? shift : 1;
    bless \$val, $class;
}
[download]

It says that you don't need to share it because it's already shared. Also, note that the author shares the scalar and then blesses it... Not the other way around.

Use the source Luke.