I agree with CubicSpine and Ovid that you might want to re-evaluate the decision to use mysql. The only advantage to using mysql in these circumstances would be to enhance your perl/database skills. If this were the only consideration then by all means, continue doing so. But, OTOH, if the following are true:

• each record in the file contains only one field, e-mail address.
• once you get the file, you are the only person using it.
• you don't expect that format of the file to change anytime soon (like by adding new fields per record).

Then there is nothing that mysql can do that you can't do faster working with plain text files.

I work with a file that has 48,193 94-byte records. On our ancient Sun Sparc 10, it takes 3 whole seconds to load the entire file and store it in an array. On our Sun Enterprise 350, it takes less than a second.

In my case, however, I have to break each record into 10 fields, be able to sort across multiple non-contiguous fields, perform merges and complex selects. So I should consider using a database implementation even though the file is used only by me and is never updated (except when I replace the entire file weekly).

"Make everything as simple as possible, but not simpler." -- Albert Einstein