I've never heard of it myself, but Wikipedia says:

PBKDF2 (Password-Based Key Derivation Function) is a key derivation function that is part of RSA Laboratories' Public-Key Cryptography Standards (PKCS) series, specifically PKCS #5 v2.0

The specification is available in RFC 2898, and I found an OSS Perl implementation on Google's code search from Palm::Keyring, which I list below:

 Thanks to Jochen Hoenicke <hoenicke@gmail.com>
# (one of the authors of Palm Keyring)
# for these next two subs.

# Usage pbkdf2(password, salt, iter, keylen, prf)
# iter is number of iterations
# keylen is length of generated key in bytes
# prf is the pseudo random function (e.g. hmac_sha1)
# returns the key.
sub _pbkdf2($$$$$)
{
    my ($password, $salt, $iter, $keylen, $prf) = @_;
    my ($k, $t, $u, $ui, $i);
    $t = "";
    for ($k = 1; length($t) <  $keylen; $k++) {
    $u = $ui = &$prf($salt.pack('N', $k), $password);
    for ($i = 1; $i < $iter; $i++) {
        $ui = &$prf($ui, $password);
        $u ^= $ui;
    }
    $t .= $u;
    }
    return substr($t, 0, $keylen);
}
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Whether it conforms to the spec or not is another question :)

If it does, consider CPAN'ing it (with the author's permission)

Clint