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

##</code><code>##

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

$mb_award = $res[0];
$mb_accept = $res[1];

##</code><code>##

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?
  ....
}