I first wrote the following to Javier Alvarado, my friend.

Regarding your interest in helping people build their confidence [and competence] in using different programming languages, have you used a visual debugger before? I used one for the first time recently and man, it cleared up so many of my questions about how Python works. And Python is my first language.

Consider the notion of presenting learners with side-by-side visual debuggers, one with the language they're comfortable with, and one that they're becoming comfortable with.

I suspect that a learner can be trusted to provide and test equivalent code, if they are comfortable enough with one language, as I'm assuming here.