Moose questions

These points are not covered in the Moose documentation:

Question: If you set an attribute in the constructor, does it override the builder?
Answer: Yes, the builder is not run.
Code:
perl -MMoose -le'package Quxx; use Moose; has "qux" => ( is => "ro", builder => "_build_qux" ); sub _build_qux { die "duck" }; package main; my $q = Quxx->new( qux => "cat" ); print "qux = #".$q->qux."#"'
Output:
qux = #cat#

Question: How do you compose a writer subroutine? (aka setter / mutator method).
Answer: You don't need to, Moose creates it for you. Just define it in the attribute and then call it.
Code:
perl -MMoose -le'package Foo; use Moose; has "foo" => ( is => "rw", writer => "_set_foo" ); sub set_foo { "bar" }; sub bar { my $self = shift; $self->_set_foo(2); }; package main; my $f = Foo->new; $f->bar(4); print "foo = #".$f->foo."#"'
Output:
foo = #2#