miguel@alice:~/jruby/upstream/jruby$ PATH=$PWD/bin:$PATH jirb
irb(main):001:0> s = String.new("").freeze
=> ""
irb(main):002:0> s.chomp!
=> nil
irb(main):003:0>

miguel@alice:~/jruby/upstream/jruby$ PATH=$PWD/bin:$PATH jirb
irb(main):001:0> s = String.new("").freeze
=> ""
irb(main):002:0> s.chomp!
RuntimeError: can't modify frozen String
        from org/jruby/RubyString.java:4286:in `chomp!'
        from (irb):2:in `<eval>'
        from org/jruby/RubyKernel.java:995:in `eval'
        from org/jruby/RubyKernel.java:1316:in `loop'
        from org/jruby/RubyKernel.java:1138:in `catch'
        from org/jruby/RubyKernel.java:1138:in `catch'
        from /home/miguel/jruby/upstream/jruby/bin/jirb:13:in `<main>'
irb(main):003:0> 

miguel@alice:~/jruby/upstream/jruby$ irb2.5
irb(main):001:0> s = String.new("").freeze
=> ""
irb(main):002:0> s.chomp!
Traceback (most recent call last):
        3: from /usr/bin/irb2.5:11:in `<main>'
        2: from (irb):2
        1: from (irb):2:in `chomp!'
FrozenError (can't modify frozen String)
irb(main):003:0>