Is undefined variable equal to nil in Ruby?

Question

I got error as undefined variable, I know nil is evaluated to false if used as boolean:

if y
  puts "Something"
end

Answer 1

There's a slight wrinkle on this. Try this:

if 5 == 0
   y = 'hi'
end

puts "hello" if y

y has been "defined" in the if block. Remove that block and this gives an error.