See tie and DB_File. A tie'd hash simply moves the storage of the hash onto disk, at the (rather huge) cost of access speed.

A hash is a data structure optimized for fast lookup by a key value. An array can only look up data fast by its index, and the array assumes that all index values are sequential. You haven't told us whether that's the case, so I'm using a hash.

For the "postfix increment" operator ("++"), see perlop. It is basically $seen{ $key } = $seen{ $key } + 1, except shorter.

In reply to Re^3: Filtering very large files using Tie::File by Corion
in thread Filtering very large files using Tie::File by elef

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