[oak perl] until loop(s)

[Steve Fink]

David Alban wrote:
> If you have:
> 
>   my $counter;
>   until ( $counter == 5 ) { ... }
> 
> Then (at least) the first time $counter is tested by the until loop,
> you're asking perl to compare the number five to $counter, which is
> undefined because it never was assigned a value.
> 
> If you first initialize $counter:
> 
>   my $counter = 0;
>   until ( $counter == 5 ) { ... }
> 
> then unless you undefine (or some operation undefines) $counter in the
> loop, you'll never be comparing a number to an undefined value.
> 
> TMTOWTDI.  I might have done your loop as:
> 
>   for my $counter ( 1..5 ) {
>     ...
>   }
> 
> if $counter wasn't needed after the loop and:
> 
>   my $counter;
>   for $counter ( 1..5 ) {
>     ...
>   }
> 
> if $counter was needed after the loop.

But not if the __value__ is needed after the loop, because 'for' will 
implicitly localize the value.

   my $counter = 10;
   for $counter (1..5) {
   }
   print $counter;

will print 10.