After a call such as $regex(b,/(a)?(b)/g), $regmlex(1,0) is set to 1, which, given the fact /F is not used, can be viewed as correct.
However $regmlex(1,1) is $null and $regmlex(1,2) is 'b', and that defies logic if $regmlex(1,0) reports 1.
This was found after a person was trying to figure out if a given capture group being reported was participating in the match, an information that can be useful when debugging.
