Why does BeanShell's interpreter re-parse a script on every execution by default?

BeanShell's classic execution model treats each eval() or source() call as interpreting the given script text fresh, walking through and executing its statements directly, rather than first compiling it into some cached, reusable intermediate form the way a JSR223 engine typically does.

This design reflects BeanShell's original goal of being a lightweight, embeddable interpreter prioritizing simplicity and direct Java-syntax compatibility, rather than being architected from the ground up for maximum repeated-execution performance the way a dedicated scripting engine with a compilation and caching layer would be.

The practical consequence is that a script called once, or occasionally, pays a modest, largely irrelevant interpretation cost, while the same script called repeatedly - like once per iteration of a high-volume load test - pays that same cost every single time, which is exactly the scenario where the performance gap versus a caching engine like JSR223's Groovy becomes noticeable.