Type=text pattern issue

I am working on a small home project and need some help. I created a test website and everything seems to work fine but I would like to add something to my user id field. The question is

Can I add more than one item for the Type=text pattern="abc.*" field

What i mean is that can i add let's say 123 as a valid pattern for the user id field so the user can login with an id whose first 3 characters begin with EITHER abc OR 123 and the webpage will know its a valid id?

I tried type=text pattern="[abc.][123.]

but it doesn't seen to accept either one only both

Thanks!

Mike R.