With -XStrict 'x', 'xs', 'y' and 'ys' don't become strict. I'm wondering about
the motivation behind this, I found this interesting. I always thought -XStrict
gives me this guarantee: If I'm using an already-defined variable(bound by a
let or pattern matching) in an expression, I can be sure that the variable
won't be bottom in that expression, because it would be `seq`d before the
expression is evaluated.