With "goatse" it's a list _assignment_ = which in scalar context returns the number of list elements assigned.
I'll have to accept that on faith. Edit: Well, I guess I don't have to take it on faith:
se strict;
use warnings;
use 5.012;
my $x = () = ('a', 'b', 'c');
#scalar context on left, a list assignment on right
#Full goatse syntax: my $x =()= ('a', 'b', 'c');
say $x;
--output:--
3
PS: you replied to yourself twice.
In my opinion, the indenting is a terrible feature. All posts in a thread should be at the same level of indenting--none. If you want to respond to a particular post, you should quote it.