plus sign appears not to work as expected

[Bill Gradwohl]

I had hoped to find a help list because this may be my problem, but here
goes:

grep --color '^[[:alpha:]]*' xxx
Lists every line including blank lines, highlighting leading alpha strings.

grep --color '^[[:alpha:]][[:alpha:]]*' xxx
Lists every line starting with an alpha and highlights all leading alphas.
This is what I wanted, so I tried rewriting the spec as:

grep --color '^[[:alpha:]]+' xxx
lists nothing.

Is it me or is this a bug?


-- 
Bill Gradwohl