It sounds like one of the columns in your table has NULL values. Try to add nvl to your SELECT statement, and also try to change

($mb_award,$mb_accept) = $dbh->fetchrow_array();
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to two steps -

use Data::Dumper;
...
my @res = $dbh->fetchrow_array();
print Dumper(@res);

$mb_award = $res[0];
$mb_accept = $res[1];
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Use the Data::Dumper module to investigate your variables - I suspect you will see an undef in @res (because one of the column might be NULL).

One last observation is that your test of greater than "0.00" does not work if both values are equal to "0.00" or one is "0.00" and the other is NULL. In other words, the test is incomplete. Perhaps you need to add some exception handling...

if ($mb_award > 0) {
  $mb_amount_disp = $mb_award;
} elsif ($mb_accept > 0) {
  $mb_amount_disp = $mb_accept;
} else {
  # both values are <= 0 or undef, what shall I do?
  ....
}
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