Edit: found the explanation for the last one: http://www.aimred.com/news/developers/2008/08/14/unlocking_t... So, basically, it's just using it as a normal case equality operator and you generally shouldn't use it in place of a regular #call.
def multiple_of( n )
lambda{ |x| x.modulo( n ).zero? }
end
case 10
when multiple_of( 3 ):
puts "3!"
when multiple_of( 4 ):
puts "4!"
when multiple_of( 2 ):
puts "2!"
end
case $stdin.gets.chomp
when lambda {|matchobj| matchobj.count("!") > 1 }
puts "Quitcher yelling!"
when "hi"
puts "Hi yourself"
end ->(x){ x % n == 0 }