You're re-preparing and re-executing your query on each pass through the loop. Is that really what you want to do? Does the value of $order change in the loop?

You should be using placeholders for your variables. Something like:

$sql =<<"SELECT * FROM tbl_admin WHERE day = '$d' AND month = '$m_num'
+ AND year = '$y' AND expal = '?' AND status= '2'";

if($order == 2 ) {
    $sql .= " ORDER BY c_name";
}
elsif ($order == 3 ) {
    $sql .= " ORDER BY expal";            
}

$sth = $dbh->prepare($sql);

foreach my $key_expal (keys %expal) {
    $sth->execute($key_expal) || die $sth->errstr;

    while ($pointer = $sth->fetchrow_hashref) {
        my $expalnum  = $pointer->{'expal'};
        my $comp      = $pointer->{'c_name'};        
        my $cltime    = $pointer->{'time'};
        my $cltime2   = $pointer->{'time2'};
        my $last_name = $pointer->{'last_name'};
        my $clnum     = $pointer->{'c_number'};
        my $status    = $pointer->{'status'};
        print "<br>L 265 - <b>$comp</b> $expalnum";
    }
}
[download]

Because %expal is a hash, your queries will be run in arbitrary order, but the results of each query should be returned in the order your query specified.

Ordering by expal is redundant, though, when you're specifying that only one expal is acceptable. You might need to rethink your query. Do you really want to use an IN:

$sql = "SELECT * FROM tbl_admin WHERE day = '$d' AND month = '$m_num' 
+and year = '$y' AND expal IN (".join(',',keys %expal).") AND status= 
+'2'";
[download]

and no outer loop?