The first one I presented is the way the Moose documentation calls has, the way the Moose test suite typically calls has, and the way I and most of the rest of the Moose Cabal call has.

The second one isn't common at all, but I have seen people both completely leave out the parentheses:

    has foo => is => 'ro', isa => 'Str', ...;

or treat has as a straight function

    has(foo, is => 'ro', isa => 'Str');

both of which cause Perl::Tidy to do weird things.