MooseX::OneArgNew lets your constructor take a single argument, which
will be translated into the value for a one-entry hashref. It is a
parameterized role with two parameters:

type
    The Moose type that the single argument must be for the one-arg form
    to work. This should be an existing type, and may be either a string
    type or a MooseX::Type.

init_arg
    This is the string that will be used as the key for the hashref
    constructed from the one-arg call to new.

Homepage:
https://metacpan.org/release/MooseX-OneArgNew
