Can you give an example?
I can't think of a single situation where whitespace matters in Ruby (unless of course you forget to put a space between two commands or something silly).
$ irb
irb(main):001:0> def foo(x=70) = x
=> :foo
irb(main):002:0> i = 2
=> 2
irb(main):003:0> foo / 5/i
=> 7
irb(main):004:0> foo /5/i
=> /5/i`foo + bar` and `foo+bar` are `foo()+bar`, but `foo +bar` is `foo(+bar)`
ternary ? : also has some interesting whitespace dependent mixups with symbols, but I cannot remember what. I think that parser has many gotchas like that, but they are really really rare to bite you, because ruby's magic follows human intuition as much as possible.