gistfile1.txt

def foo(var, hash1={}, hash2={})
  puts "var: #{var.inspect}"
  puts "hash1: #{hash1.inspect}"
  puts "hash2: #{hash2.inspect}"
end

> foo('x', 'y', 'z')
var: "x"
hash1: "y"
hash2: "z"

> foo('x', {'y'=>1, 'z'=>2})
var: "x"
hash1: {"y"=>1, "z"=>2}
hash2: {}

> foo('x', 'y'=>1, 'z'=>2)
var: "x"
hash1: {"y"=>1, "z"=>2}
hash2: {}

> foo('x', {'y'=>1}, {'z'=>2})
var: "x"
hash1: {"y"=>1}
hash2: {"z"=>2}

> foo({'y'=>1}, {'z'=>2})
var: {"y"=>1}
hash1: {"z"=>2}
hash2: {}

> foo('y'=>1, 'z'=>2)
var: {"y"=>1, "z"=>2}
hash1: {}
hash2: {}