...aaaand...with Flexible Logic.... Now We Don't Have To Worry About FALSE (or NO, or OFF) Either!
We're down to just one "branch inhibitor": The ~null~ antiform (and maaaaybe ~NaN~)
So the rule is simple. MATCH Errors on NULL Input...
...unless you use the /META refinement!
>> match/meta [~null~ integer!] 10
== '10
>> match/meta [~null~ integer!] null
== ~null~
>> match/meta [~null~ integer!] <some-tag>
== ~null~ ; anti
As usual, where there's an isotope, there's a way. 