If you just want to set the initial state, you should either use builder, or the aptly-name 'default'.

has 'foo' => (
  builder  => 'build_foo',
);

sub build_foo {
    my $self = shift;
    return 'blah';
}

# OR

has 'foo' => (
    default => sub {
        my $self = shift;
        return 'blah';
    },
);
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