sub Prioritise_requests
{
  my( $input_directory, $node ) = @_;

  for my $dir_num ( '1', '2', '3' )
  {
    my $input_dir = $input_directory.$dir_num;

    opendir DIR, $input_dir or die "Error opening directory $input_dir - $!";
    my @files =
      sort { -M $a <=> -M $b }
      map "$input_dir/$_",
      grep /^Flat_file.*\.txt$/,
      readdir DIR;
    closedir DIR;

    foreach ( @files )
    {
      if ( Is_the_file_mine($node, $_) and Do_I_run_the_request_now($_) )
      {
        move $_, $input_directory or warn "Error moving $_ to $input_directory - $!";
        return;
      }
    }
  }
}