var = 'abc,d'
m/,/: not matches
y/,/,/: not matches
! m/,/: not matches
! y/,/,/: not matches
var = 'abcd'
m/,/: matches
y/,/,/: matches
! m/,/: matches
! y/,/,/: matches
var = 'a,b,c,d'
m/,/: not matches
y/,/,/: not matches
! m/,/: not matches
! y/,/,/: not matches