B::Deparse can be illuminating

$ perl -MO=Deparse,-p temp.pl
sub testing () {
    foreach $_ (@_) {
        print($_);
    }
}
(my $subref = \(&testing(1, 2, 3, 4, 6)));
print(Dumper $subref);
(my $subref = (\&testing));
__DATA__
temp.pl syntax OK
[download]