Update: This node is based on a mistake, the statements below are false. See Re: Re: Lexicals in if() scope gotcha!.

I fell through this trap when I wrote something like this:

for my $n (1..256) {
 .... do something ....
 }
for my $n (1..32) {
 ... do sthg else ...
 }
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The difference is that as for localizes the looping variable (even if it's not my, but a global), it's just stupid to have it outside the loop's scope. It might be useful to access it after the loop when you're writing a for(;;) loop or an if() conditional.

While this is a bit counter-intuitive for me too, it does have some logic. Perl is just not C++ (where you can put a declaration in the first argument of for(;;;)).