[ki_]

! ignores the function error (only possible with void return types)

!? provides an alternative value when the function errors

!! exits the current scope on an error, e.g. return,continue,exit,...

It doesnt seem that complex. Ofcourse, there is also '??' and '?!'. That might make it more difficult. It's not vague actually. if it starts with '!', it's a function error handler. if it starts with '?', it's a null-check.