> It's very rare that any programmer switches computer languages.

Or is it?

I regularly use six different languages of three paradigms and various abstraction levels, and this doesn't count DSLs nor Turing-complete tools like make. Of my colleagues from current job, half of the more experienced set write in at least three languages as well. Of the team from my previous job, all of them are polyglots. And of course none of us started with all the languages, we picked them up as needed and wanted.