while (my $line = <$DATA_IN>) { 
     if ($line =~ m[^\w{4} (\d\d?)/(\d\d?)/(\d{4}) \d\d?:\d\d?]) { 
          chomp $line; # removes trailing carriage return 
          my $new_date = "$3 $1 $2"; # new order of date components 
          $line = "$line $new_date \n"; # add new date format to existing line 
     } 
     print $DATA_OUT $line; 
}