When you have many records to check in the way you are describing, perhaps is time to consider a database. What you are asking could be done very easily with a DBMS.

Checking for strings in both lists (INNER JOIN) or for strings in the first list without corresponding items in the second list (LEFT OUTER JOIN) are easy tasks for a DBMS.
Once you have paid the price of inserting the lists in two database tables and setting up the appropriate indexes, you have a dedicated server that can solve this kind of problems much better than any implementation you or me can write in any language.

If you don't want to commit to a complex client/server database, you may give a thought to DBD::SQLite.

In reply to Re: comparing a string with lots of other strings by Anonymous Monk
in thread comparing a string with lots of other strings by matthewsnape

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