Here is a little more info. I added the following code inside the subroutine:

        my $socketname = shift;
        print "\$new_sock=$new_sock\n";
        print "\$socketname=$socketname\n";
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And got this output:

$new_sock=IO::Socket::INET=GLOB(0x8130a94)
$socketname=*main::new_sock

But I still don't know enough about this stuff to know what I'm doing wrong.