o-based indexing. When substring expansion of the form ${param:offset[:length} is used, an `offset' that... returns with code one.
An option must be of the form --option, only characters in the ranges A-Z, a-z,... returns with code one.
An option must be of the form --option=value, only characters in the ranges A-Z... rns with code one.
A brief option must be of the form -a, only characters in the ranges A-Z, a-z, 0-9 a
