$counter = 1;
open(DATA, "export.dat")||die "Cannot open export.dat for read:$!\n";
while(<DATA>){

  $temp_line = $_;

  if($temp_line =~ /^1(\d*)/){
    if($counter > 1 ){ #No temp file yet if this is the first record
      close TEMP||die "Cannot close temp.dat:$!\n";
     	&output_data();
    }
    open(TEMP, ">$temp.dat")||die "Can't open temp.dat:$!\n";
    print TEMP $temp_line;
  	$counter ++;
  }
  elsif(/\S+/){
    print TEMP $temp_line;
  }
}
close DATA||die "Cannot close $in_dir/export.dat (weird):$!\n";
close TEMP||die "Cannot close $in_dir/temp.dat:$!\n";
&output_data();

sub output_data{
  #do stuff with temp.dat
}