Overall, it's pretty good. Good enough that I have a hard time believing your claim that this is your "first go at doing perl." :-)

If you don't want to use grinder's spew script (say you don't have /dev/urandom for instance) you might consider making this:

my @chars = ('a'..'z', 'A'..'Z', 0..9);
my $plaintext_pass = do {{
  local $_ = join "" => map {$chars [rand @chars]} 1..8;
  redo unless /[a-z]/ && /[A-Z]/ && /\d/;
  $_;
}};
[download]

a little more readable like this:

my @chars = ('a'..'z', 'A'..'Z', 0 .. 9);
my $plaintext_pass;
PICK: {
    $plaintext_pass = '';
    $plaintext_pass .= $chars[rand @chars] for 1..8;
    /[a-z]/ && /[A-Z]/ && /\d/ or redo PICK for $plaintext_pass;
}
[download]

shrug

You might also want to reuse @chars in the list you use when picking the salt.

I agree with grinder's suggestion that using a module to send the mail is cleaner. I also agree with his suggestion that you re-scrub your variables.

Edit: Password picking code fixed to squash the bug that Arien pointed out in his reply. Arien++

-sauoq
"My two cents aren't worth a dime.";