-- normal completion --
x=1
x=2
close a err=nil
-- break closes the closing value --
x=1
close b err=nil
-- error in body: closing runs with the error, then it propagates --
close c err=close_for_iter:22: body boom
ok=false is_string=true
-- nil closing value (pairs): nothing to close --
k=1
k=2
-- non-closable closing value is a catchable error --
false	close_for_iter:30: variable got a non-closable value
-- nested for-loops close inner then outer --
a=1 b=1
close inner err=nil
close outer err=nil