[thelist] regex: 0-1 range VS optional

[Brian Cummiskey]

Both of these seem to work for all my cases, but i'm not sure which is 
the better version to use.

I need to validate some item numbers, which come in one of 3 formats:

normal:  123456  (1 to 7 digits in length)
drop ship:  D123456 (gets a D prefix)
child item:  123456A (gets a single letter suffix)
and there can also be drop ship child items, as in D123456A

I've come up with two versions which both appear to negate bad entries 
correctly, but i'm not sure which is considered more proper:

^(d|D)?[0-9]{1,7}([a-zA-Z]{0,1})$
^(d|D)?[0-9]{1,7}([a-zA-Z]?){1}$

the first allows either 0 or 1 letters at the end, where as the second 
allows 1 letter, optionally.