gistfile1.txt

$ JRUBY_OPTS="--2.0" irb
jruby-1.7.18 :001 > def foo(a, b, **options)
jruby-1.7.18 :002?>   puts [a, b, options].inspect
jruby-1.7.18 :003?>   end
 => nil
jruby-1.7.18 :004 > foo(1, 2)
[1, 2, {}]
 => nil
jruby-1.7.18 :005 > foo(1, 2, 3)
ArgumentError: wrong number of arguments (3 for 2)
        from (irb):5:in `evaluate'
        from org/jruby/RubyKernel.java:1107:in `eval'
        from org/jruby/RubyKernel.java:1507:in `loop'
        from org/jruby/RubyKernel.java:1270:in `catch'
        from org/jruby/RubyKernel.java:1270:in `catch'
        from /usr/local/rvm/rubies/jruby-1.7.18/bin/irb:13:in `(root)'
jruby-1.7.18 :006 > foo(1, 2, a: 1)
[1, 2, {}]
 => nil
jruby-1.7.18 :007 > foo(1, 2, a: 1, b: 2)
[1, 2, {}]
 => nil

gistfile2.txt

$ rvm 2.1.0 do irb
2.1.0 :001 > def foo(a, b, **options)
2.1.0 :002?>   puts [a, b, options].inspect
2.1.0 :003?>   end
 => :foo
2.1.0 :004 > foo(1, 2)
[1, 2, {}]
 => nil
2.1.0 :005 > foo(1, 2, 3)
ArgumentError: wrong number of arguments (3 for 2)
        from (irb):1:in `foo'
        from (irb):5
        from /usr/local/rvm/rubies/ruby-2.1.0/bin/irb:11:in `<main>'
2.1.0 :006 > foo(1, 2, a: 1)
[1, 2, {:a=>1}]
 => nil