But the specific design of Frawk is that it's statically typed. Hence both the title of this thread and the description in the linked documentation. If Frawk sees that you've got a variable N, and you add 1 to it, Frawk concludes that's a number. Seems fair enough and it makes Frawk faster.

However for example, Frawk may be quite sure that something is a number, and so when there isn't a value for that - Frawk says the value is a zero. But Awk isn't fixated on the idea that it's always a number, if there's no value awk will say it is the empty string, and why not.

Lots of Awk programs don't care, but if yours does it will behave differently under Frawk.