Granted, a.b = 12; is much nicer looking than a.set_b(12); or a.set_b = 12
(Other post: If it's supposed to be an assignment it should look like an assignment, and setting a property or attribute is an assignment no matter how it's mediated under the hood.)

FYI, in case you didn't know about it already, Attribute::Property makes a->b = 12 work in Perl 5. From its synopsis:

my $object = SomeClass->new(digits => '123');

$object->nondigits = "abc";
$object->digits    = "123";
$object->anyvalue  = "abc123\n";

$object->anyvalue('archaic style still works');

my $john = Person->new(name => 'John Doe', age => 19);

$john->age++;
printf "%s is now %d years old", $john->name, $john->age;
[download]

When modifying a value using an accessor method (which we dubbed 'archaic style'), things get ugly:

Old:
$john->age($john->age + 1);
$john->name->(do { (my $n = $john->name) =~ s/Doe/Smith/; $n });

New:
$john->age++;
$john->name =~ s/Doe/Smith/;
[download]

Juerd # { site => 'juerd.nl', plp_site => 'plp.juerd.nl', do_not_use => 'spamtrap' }