Apart from what $code or die said, there are a couple of other things.
Can you see anything wrong with this:

$mail_prog = "/usr/sbin/sendmail -t";
open(MAIL, "|$mail_prog -t");
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Apart from the fact these variables don't have their scope declared (see strict and my) you are passing sendmail two -t switches.

And the last thing, though it's no real problem, just a question of clarity and style is to use a heredoc instead of multiple prints.

print MAIL <<"MESG";
To: $recipient
From: $sender
Subject: database entry

added

---------------------------------------------------
.
MESG
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