my $sort_order = $q->param('sort_order');
my $order      = $q->param('order');
print '<tr>';
foreach(@column_headings){
    print "<td><A href=\"pastRequests.pl?order=$_&sort_order=" . 
          (($_ eq $order && $sort_order eq 'desc') ? 'asc' : 'desc') .
          "\">$_</a></td>";
}
print '</tr>';

my @records = ##Get your data, maybe an array of hashes??
@records = reverse(@records) if($sort_order eq 'asc');
foreach(@records){
  ##Output records
}