parentheses missing in action

[Anonymous Monk]

I'm using autodie so this seemed reasonable:

open my $pipe, $cmds;

But perl warns: Parentheses missing around "my" list at ...

It works but it warns and I know why. All of the following work too and silence the warning:

open (my  $pipe,  $cmds);
open  my ($pipe), $cmds;
open  my  $pipe, ($cmds);

1. seems most correct.
2. also seems correctish.
3. what is going on here?

[Corion]

See https://github.com/Perl/perl5/pull/24378, which discusses the heuristic.