I teach a Perl class one semester a year. For awhile I was writing a lot of cgi scripts that kept me "in shape", but that has dropped to zero.

I find that it comes back pretty quickly (as long as I keep a reference handy). That and that the act of explaining it to students does a good job of reteaching it to me. (I'm less than certain that my students get it).

I think I even get a little better each time. I finally (1/2) understand Perl objects

Time flies like an arrow, fruit flies like banannas