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In his presentation at RubyKaigi 2022, Jeremy Evans discusses the historical issues of assignment evaluation order in Ruby and the subsequent fixes made in Ruby 3.1 and 3.2. He highlights two main problems: inconsistencies in the evaluation order of multiple assignments and constant assignments, both of which failed to adhere to the left-to-right evaluation principle in earlier Ruby versions.

Key points of the presentation include:  
- **Definition of Assignment Evaluation Order**: Evans explains that every assignment expression in Ruby has a specific order of evaluation, which is crucial for understanding how code executes.  
- **Historical Issues**: He illustrates that prior to Ruby 3.1, multiple assignments could lead to unexpected results because Ruby evaluated them in a manner contrary to the principles developers relied upon. An example is provided where the order of method calls was not maintained as intended.  
- **Complexity of Fixing Bugs**: The presentation emphasizes the challenges involved in correcting these evaluation order issues, particularly due to the stack-based architecture of Ruby’s virtual machine, which complicated the management of evaluations.  
- **Instruction Differences in Ruby Versions**: Evans presents a comparison between Ruby 3.0 and 3.1, showing how bug fixes resulted in changes to the virtual machine instructions, affirming how the left-to-right evaluation principle was implemented in the latter version.
- **Conclusion and Takeaways**: He concludes by reinforcing that old bugs can still be addressed, and not all bugs that are difficult to fix should be dismissed. Older bugs might indicate underlying issues that could provide opportunities to deepen one's understanding of Ruby.
Through this presentation, Evans hopes to educate attendees on the intricacies of Ruby's evaluation order and encourage them to explore more about Ruby programming techniques.

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