When I was choosing between learning python and perl in the late 90's, it was the context sensitivity of perl expressions which really squicked me. To me, that was the critically bad language decision in perl. You can make context-sensitive expressions in python (using operator overloading, for instance), but you have to go out of your way to do it in one way or another. In perl you can easily do it by accident, and it can result in serious bugs. It seemed masochistic, to me.