Rails routes with not-equal-to constraint -

I would like to add a non-equal-barrier on my route rules, in particular, I would like to claim that no parameters Should not be equal to anything. For example, in the following code:

get ': menu /: submenu', barriers: {# add something here} .

I want to implement that code: is not equal to abc . I have tried to write the submenu: / (?? ABC) / as an obstacle, but does it affect any other param any suggestions?