NHF – new heroes for Heroes V 3.1.

Don't you test your scripts on a map? It seems fine at first glance, but you never know...

Yes. In combination with min, it works correctly. If an enemy town is closer, it returns its name; if it's your own town, it returns nil. It also returns nil if the hero is in a town, is dead, or is on a level where there are no towns. However, for the latter, you need to add

if not targetTown then
	return nil;
end;

after defining targetTown.