ReciPants

DBD::Pg
Database driver for Postgres
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DBD::mysql
Database driver for MySQL
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DBD::Oracle
Database driver for Oracle

Math::Fraction
Decimal <-> string fraction conversion

Digest::SHA1
SHA-1 digest/hash for tamper-proof user cookies

Net::SMTP
Send email via SMTP. Not required if you use sendmail.

Database

Postgres v7.x or higher
----- or -----
MySQL v3.2 or higher
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Oracle v8 or higher (7 should work, but is untested)

sendmail

Not required if you use the Net::SMTP module.