alternation option end of string

Ray Andrews <[email protected]> Fri, 1 May 2026 15:31:18 -0700
Newsgroups gmane.comp.shells.zsh.devel,gmane.comp.shells.zsh.user
Message-ID <[email protected]>
I know how to do an alternation, but how do you make one of the choices 
'nothing' meaning end of string?