In the talk "Pre-evaluation in Ruby" presented by Kevin Newton at RubyKaigi 2019, the speaker explores an optimization technique in Ruby called pre-evaluation. This approach aims to enhance Ruby's performance, acknowledging the language’s historical difficulties with optimizations due to its flexibility and productivity features that often come at the expense of performance. The talk covers several important aspects related to how pre-evaluation works and its implications for Ruby programming.

Key points discussed include:
- Programming Compiler Steps: The presentation begins with an overview of the process that Ruby compilers follow, including stages like lexical analysis, semantic analysis, and instruction generation for the virtual machine.
- Lexical and Semantic Analysis: Deisz explains lexical analysis as the breakdown of sentences into tokens, followed by creating an abstract syntax tree (AST) through semantic analysis to understand the relationships between those tokens.
- Performance Limitations: He addresses Ruby's limitations in executing optimizations at runtime and the inherent constraints of Ruby's virtual machine. Notably, he states that certain decisions need to be made at compile time rather than runtime due to these limitations.
- User Participation in Optimizations: Users can opt into performance improvements by limiting their usage of Ruby features. This concept allows for better compiler optimizations, although complex Ruby expressions may pose challenges.
- Introduction of pre_val: The introduction of the pre_val gem enables developers to analyze their Ruby code and identify potential compile-time optimizations. The gem utilizes Ripper to generate the AST and thus automates the source code adjustment for better optimization.
- Demonstration of Sinatra App: Deisz provides a demonstration of a Sinatra application leveraging the pre_val gem to showcase how real-time optimization can be achieved in Ruby code.
- Enhancements through Collaboration: The talk emphasizes the importance of community feedback for building efficient optimizations and maintaining usability without sacrificing performance. Deisz encourages ongoing collaboration within the Ruby community.

In conclusion, Deisz reinforces that while Ruby's flexibility can complicate optimizations, tools like pre_val aim to bridge this gap, making Ruby code clearer and more performant. These efforts ultimately contribute to the ongoing evolution and robustness of the Ruby programming language.