You'd better go check your logs to see what the script is complaining about (I bet there's some useful info in there ;-)

I would slightly alter your code though, using placeholders (and die with the error message):

$sth = $dbh->prepare("INSERT INTO email (f_name, l_name, code, ext, em
+ail)
                      VALUES (?,?,?,?,?)");
$sth->execute($FNAME, $LNAME, $STR, $CT5, $EMAIL) || 
   die $sth->errstr;
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And don't forget we have some nice Tutorials on DBI related subjects :)