Another thing I haven't seen mentioned yet:

When dealing with nested constructs like this, I find it useful to dereference each level into a temp variable, rather than sling around nested refs. Makes the code easier to read, brings your assumptions about the data's structure to the front, and prevents problems like this, but at a cost in speed and space. I think it's usually a good tradeoff.

So you'd have:

my $lines = $FULLLINES{$key};
my $num   = scalar @$lines;
[download]

instead of Hofmator's

my $num = @{$FULLLINES{$key}};
[download]

It doesn't make a big difference here, but with deeply nested structures it's invaluable.

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F o x t r o t U n i f o r m
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The hell with paco, vote for Erudil!