1. Is it possible to write an array to disk in the same way as you can a hash, with either the dbmopen/dbmclose or that tiehash thing?

You can design a class which will do that for you. Take a look at perldoc -f tie

How can I sequentially step through elements in a hash? For example with an array I would just 'push' things on, then I 'shift' them off

Use each.

If I don't know the key from my hash, how can I just retrieve the first value

In a hash, there is no such thing as "the first value" because hashes are not ordered. You can get _a_ value from your hash by using each().

Example

my %hash = ('foo' => 'bar', 'bar' => 'foo');
my ($key, $val) = each(%hash);
print "$key\n";
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--perlplexer