I'm still playing with the @REGEX thing. In the latest incarnation of my plugin @XMATCH, it returns the number of matches and sets the plugin _GMATCH to the number of groups matched. When used together in the command, like this
it seems the two variables are evaluated left to right. Is that reliable behavior?
v:\> echo %@xmatch[(i)|(s)|(q),Mississippi] %_gmatch 8 2