R4RS 4.2.1  (or <expression> ...)  ==>  obj

The <expression>s are evaluated from left to right, and the value
of the first expression that evaluates to a true value (see section
see section 6.1 Booleans) is returned. Any remaining expressions
are not evaluated. If all expressions evaluate to false values, the
value of the last expression is returned. If there are no expressions
then #F is returned.

(or (= 2 2) (> 2 1))    ==>  #t
(or (= 2 2) (< 2 1))    ==>  #t
(or #f #f #f)           ==>  #f
(or (memq 'b '(a b c))
    (quotient 3 0))     ==>  (b c)
