local variables in Perl and Lua

I didnt get an answer for this in the Python thread, so I'll ask here: Why do variables have to have the local keyword to make their scope local? Why cant it just use implicit lexical scope like most any other languages?

>>32
Every keyword in lua is long. "function" is longer than "lambda" which is longer than "fn" but really who cares? it's just a bit of typing
Too verbose to read. Lambda, fun, λ are ok.