#use strict; #uncomment to kill the code
my $s = 'foo';
$$s = 'bar';
print "\$foo = $foo\n";
$foo = 'baz;
print "\$\$s = $$s\n";

__END__

Output:
$foo = bar
$$s = baz

##</code><code>##

if ($#-) {
    no strict 'refs';
    print "$#+ matches found", $/;
    for (1..$#+) {
        print "\$_ is $_, & \$1 is $1", $/;
        print  "$haystack contains ${$_} at $-[$_]", $/;
    }
}