My brain is almost fifty years old... and I don't find that fact to be relevant. I have to switch back and forth, because I don't have time to duplicate CPAN in GEMS. I find that I do occasionally get tripped up by syntax, but mostly my brain can keep its associations separate. It does help that Ruby has added pragmatic forms of RegEx matching that mirror Perl's, but I consciously use OO RegEx when in Ruby to keep myself in that mode as much as possible. I find that I can switch gears and be productive within an hour. Certainly I miss what isn't easy in one language or the other, but I choose the language I use based on the project requirements, so I eliminate grass-is-greener regrets early in the development cycle.