[c-nsp] as-path access-list question

[Paul Stewart]

Pardon my ignorance but I can't seem to find an answer on this...

I've been playing around with our BGP reach to an upstream provider and
I'm trying to find something *between* 

ip as-path access-list 20 permit ^6539$

and

ip as-path access-list 20 permit ^6539_[0-9]*$

Is there a syntax that is "in between" these two?  Any references on
Cisco for this?

Thanks in advance,

Paul