Review

• visibility
• is (rw or ro)
• usually what you want
• reader/writer/accessor/init_arg
• customize the naming
• default
• provide a default value
• must be a coderef (don't want to share ref between instances!)
• required
• is the value being undefined OK?
• type constraints
• isa => ...
• make your own with Moose::Util::TypeConstraints