jruby-9.4.0.0 :002 > str = "123456789" * 100 # 10 isn't enough
 =>  "..."
jruby-9.4.0.0 :003 > str.each_char.each_slice(2){|a, b| (a.ord ^ b.ord)}
org.jruby.ir.IRScope.cloneInstrs(IRScope.java:588): Java::JavaLang::NullPointerException
        from org.jruby.ir.IRScope.prepareForCompilation(IRScope.java:655)                                                       
        from org.jruby.runtime.MixedModeIRBlockBody.promoteToFullBuild(MixedModeIRBlockBody.java:159)
        from org.jruby.runtime.MixedModeIRBlockBody.commonYieldPath(MixedModeIRBlockBody.java:142)   
        from org.jruby.runtime.IRBlockBody.doYield(IRBlockBody.java:170)                             
        from org.jruby.runtime.BlockBody.yield(BlockBody.java:108)                                   
        from org.jruby.runtime.Block.yield(Block.java:188)                                           
        from org.jruby.RubyEnumerable.lambda$each_sliceCommon$5(RubyEnumerable.java:1262)            
        from org.jruby.runtime.BlockCallback.call(BlockCallback.java:54)                             
        from org.jruby.runtime.CallBlock.doYield(CallBlock.java:102)                                 
        from org.jruby.runtime.BlockBody.yield(BlockBody.java:116)                                   
        from org.jruby.runtime.Block.yieldValues(Block.java:234)                                     
        from org.jruby.RubyEnumerator$1.call(RubyEnumerator.java:406)                                
        from org.jruby.runtime.BlockCallback.call(BlockCallback.java:58)                             
        from org.jruby.runtime.CallBlock.doYield(CallBlock.java:97)                                  
	from org.jruby.runtime.BlockBody.yield(BlockBody.java:108)
	from org.jruby.runtime.Block.yield(Block.java:188)
	... 183 levels...