Brilliant, Closure on Closures did it for me. The summing up in particular...

a closure is a subroutine which wraps around lexical variables that it references from the surrounding lexical scope which subsequently means that the lexical variables that are referenced are not garbage collected when their immediate scope is exited

This story has a sad end, however. To test my knowledge new-found knowledge, I wrote the following.

sub make_two_counters {
    my $count = 0;
    return sub{ $count++ }, sub{ $count+=10 }
}

my ($counter_plus_one, $counter_plus_ten) = make_two_counters();
print $counter_plus_one->() . "\n";
print $counter_plus_one->() . "\n";
print $counter_plus_ten->() . "\n";
print $counter_plus_one->() . "\n";
print $counter_plus_one->() . "\n";

__OUTPUT__
0
1
12
12
13
[download]

I was expecting this to print 0,1,11,12,13 - on the grounds that my two anonymous subs would be saving the same reference to the lexical ($count). But it seems to have merged two of my adds in together!! Help.

BTW: Thanks for all the replies ++

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