Scalability : You might want to take a look at Mail::Bulkmail. If you cannot use that, which is a shame, the way you are doing this is re-starting sendmail for each email address. Rather than sendmail, i would suggest using SMTP (there are a few modules for this).
Looking forward : When you go to mysql, make sure to us DBI, this is not usually a problem with MySQL, but always like to remind people that DBI is nice.

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_{can't sleep clowns will eat me}
-- MZSanford