When you hit the run button, Repl.it might do some unnecessary things. Like re-compile your entire projects when you might not need that. It also might re-save your project which might make your REPL a little slow.

To avoid this, create a bash REPL. And insert your project there. When someone hits the run button on your project, it'll run the bash REPL. So, you have complete control over what the run button does.