Yuck! Use use vars. 

{ use vars qw( @cache @n ) }
{@cache = (0, 1)}
sub fib {
    {push @n, shift}
    {return pop @n if $n[-1] < 2}
    {$cache [$n[-1]] ||= fib ($n[-1] - 1) + fib ($n[-1] - 2)}
    {return $cache[pop @n]}
}

[download]

Bonus: Doesn't confine you to the main namespace!

Now if we could only localize variables, we wouldn't need to manage our own stack. 

{ use vars qw( @cache ) }
{@cache = (0, 1)}
sub fib {
    (local (our $n = shift)) && do {
        {return $n if $n < 2}
        {$cache[$n] ||= fib ($n - 1) + fib ($n - 2)}
        {return $cache[$n]}
    }
}

[download]

Bonus: Don't have to use use vars except for globals!

By the way, the body simplifies down to a single expression, and your cache initialiser is not needed. 

{ use vars qw( @cache ) }
sub fib {
    (local (our $n) = shift), (
        $n < 2 ? $n : $cache[$n] ||= fib ($n - 1) + fib ($n - 2)
    )
}

[download]

Update: Replaced buggy
(local our $n = shift) && ...
with
(local (our $n) = shift) && ...

In reply to Re^2: Programming in Perl without semicolon by ikegami
in thread Programming in Perl without semicolon by buetow

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