The solutions you are getting don't all do the same thing because there are ambiguities in your question.

• Do you want 100 id per file or at most 100 lines per file?
• If the latter, are you ok with splitting ids across multiple files?
• If not, what should the code do if there are more than 100 lines for one of the ids?

Thanks for all of your help. If there would never be more than 17-18 lines per Id.

I suppose that answers the third question, but what about the two more important questions?

 
use strict;
use warnings;
my ($FH, $OUT,$past,$record,$count);
open ($FH,"<","$ARGV[0]");
$record="";
$count=0;
while ($line=<$FH>){
   my($key ,@record)=split(/\s+/, $line);
   if $past ne $key){
      $count++;
      if ($count == 100){
         open ($OUT, ">" $past);
         print $OUT $record;
         close $OUT;
         $record="";
         $count=0;
      }
      $past=$key;
   }
   $record.= $line;
}
open ($OUT, ">" $past);
print $OUT $record;
close $OUT;
[download]

Something like this may work (UNTESTED):

#!/usr/bin/perl
use warnings;
use strict;

$inFile = shift or die "usage: $0 filename\n";
open DATA, '<', $inFile or die "Cannot open '$inFile' $!";

my ( $file_count, %records );
while ( my $line = <DATA> ) {
    if ( 1 == $. || 100 == keys %records ) {
        ++$file_count;
        open OUT, '>', "file$file_count" or die "Cannot open 'file$fil
+e_count' $!";
        %records = ();
        }
    my $key = substr $line, 0, 9;
    $records{ $key }++;
    print OUT;
    }
[download]

while there's a next line
    extract the ID
    check if ID matches the previous ID
    if not:
       set previous ID to current ID
       increment a counter
       if counter > 100
            close current output file
            open a new output file
            reset counter
    
    write the line to the current output file.
[download]

Try to write that in perl you can almost translate it directly. If you have troubles with a specific step, shows us what you've tried and where your problem is.

That can create empty files. Fix:

while there's a next line
    extract the ID
    check if ID matches the previous ID
    if not:
        set previous ID to current ID
        increment a counter
        if counter > 100
            close current output file
            reset counter
    
    if output file isn't open
        open a new output file

    write the line to the current output file.
[download]

It can also create files with more than 100 records. Fix:

my $last_id;
my @group;
my $fh;
my $line_counter = 0;
my $file_counter = 0;

sub output {
    if ($line_counter + @group > 100) {
        $fh = undef;
        $line_counter = 0;            
    }

    if (!defined($fh)) {
        my $fn = sprintf('file%04d', $file_counter++);
        open($fh, '>', $fn)
            or die("Error create file $fn: $!\n");
    }

    $line_counter += @group;
    print($fh splice(@group));
}

while (<>) {
    my ($id) = /^(\S+)/;
    $last_id = $id if !defined($last_id);

    if ($id eq $last_id) {
        push @group, $_;
    } else {
        output();
    }
}

output() if @group;
[download]

If there's more than 100 record for one id, it'll put them in the same file despite the limit.

Note that both my code and the parent's pseudocode assume that the records are grouped by id in the input file.

#!/usr/bin/perl -w
use strict;
use warnings;
# my $inFile = shift(@ARGV);
# open(DATA, $inFile);
# for easier testing use data from end of file
my $recordNameOld = '';
my @buffer = ();
my $recordCount = 0;
my $MaxRecords = 3;    # only 3 for testing !
my $recordFile = 'RecFile000';
while (<DATA>) {        # read next available line into $_
    /^(\w+)/ or die "-ERROR- line $. no leftbound recordName found !";
    my $recordName = $1;
    if ($recordNameOld ne $recordName) {
        $recordNameOld  = $recordName;
        if (@buffer) {
            print join('',@buffer);
        }
        @buffer = ();        # reset buffer
        unless ($recordCount % $MaxRecords) {
            close REC    if ($recordCount);
            $recordFile++;
            my $file = $recordFile . '.txt';    # add file-type (& pat
+h)
            open(REC,'>',$file) or die "-ERROR- failed to create $file
+ $!";
            select(REC);        # now all print are directed to REC
            $recordCount = 0;
        }
        $recordCount++;
    }
    push(@buffer,$_);        # store current line
}
print join('',@buffer) if (@buffer);
close REC;
#------------------- data for testing -----
__DATA__
A5273KRU9   CA000120060919A5273KRU9   C  00000000  A                  
+          
A5273KRU9   CA300120080518 211558 USEDT                               
+          
A5273KRU9   CB0001000000380000 N2 201310201200305282003102020121020FX 
+          
A5273KRU9   CB100100038359ANDN            00000001000EUREUREUR   00000
+0000000   
A5273KRU9   CB2001A AF N    C N 0000000000000000 0000000000000000  000
+00000     
A5273KRU9   CB300100000001000000000001000000000001000000000000000     
+          
A5273KRU9   CC4001F S 0000000000000000    0000000000000000    00000000
+00000000  
A5273KRU9   CDA001REPUBLIK OESTERREICH                                
+          
A5273KRU9   CD0001REBUBLIK OESTERREICH           EURO$ MTN 144A13     
+          
A5273KRU9   CD1001OUTFBGZ 000000  0        1 4  000010000000EUR00Y    
+ ATAT  G Y
A5273KRU9   CD20012003052801058231700000 00000099679000EURF0   N      
+          
A5273KRU9   CD3001  00105823200000  320060901                         
+          
A5273KRU9   CD5001C AP15 2003052800000000   PRIV                      
+     N    
A5273KRU9   CI000100000000000000000000000000000000      00000000000000
+0000380000
A5273KRU9   CI1001A 000     00000000000000   BN 000000000000000000    
+          
A5273KRU9   CR1001    00000000            00000000            00000000
+          
A5273KRU9   CX0001A5273KRU9         016947857              7742543AT00
+00385992  
A5273KRU9   CX4001                                                    
+          
A9294WLR3   CA000120050415A9294WLR3   C  00000000  A                  
+          
A9294WLR3   CA300120090305 142038 USEST                               
+          
A9294WLR3   CB0001000000000000 F3 201107013200307012003110100000000   
+          
A9294WLR3   CB100100000000 NUN            00000001000      USD   00000
+0000000   
A9294WLR3   CB2001E AF N    C N 0000000000000000 0000000000000000  000
+00000     
A9294WLR3   CB300100000000000 00000000000 00000001000000000000000     
+          
A9294WLR3   CDA001VORARLBERGER LANDES UND HYPOTHEKENBANK AG VORMALS HY
+POTHEKENBA
A9294WLR3   CD0001VORARLBERGER LANDES UND HYPOTH RANGE ACRL VAR11     
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A9294WLR3   CD1001OUTFBPN 000000  0        3 4  000010000000USD00Y    
+ AUUS  A N
A9294WLR3   CD20010000000000000000000000 00000000000000   S4          
+          
A9294WLR3   CD3001  00000000000000   00000000                         
+          
A9294WLR3   CD5001       0000000000000000                             
+     N    
A9294WLR3   CI000100000000000000000000000000000000      00000000000000
+0000000000
A9294WLR3   CI1001C 000     00000000000000   DN 000000000000000000    
+          
A9294WLR3   CR1001    00000000            00000000            00000000
+          
A9294WLR3   CX0001A9294WLR3                                           
+          
A9294WLR3   CX4001                                                    
+          
C63278AX0   CA000120050425C63278AX0   C  00000000  A                  
+          
C63278AX0   CA300120090707 100627 USEDT                               
+          
C63278AX0   CB0001000000512500 N5 201012291200302192003122920091229AFG
+          
C63278AX0   CB100100049261AN N            00000001000CADCADCAD   00000
+0000000   
C63278AX0   CB2001A AF N    C N 0000000000000000 0000000000000000  000
+00000     
C63278AX0   CB300100000001000000000001000000000001000000000000000     
+          
C63278AX0   CC00012003021910000000000000000000000000000000000000002003
+0219 0030A
C63278AX0   CC2001  2003021910000000    0000000000000000    0000000000
+000000    
C63278AX0   CC4001A M 0000000000000000    0000000000000000    00000000
+00000000  
C63278AX0   CDA001PROVINCE OF NEWFOUNDLAND AND LABRADOR               
+          
C63278AX0   CD0001PROVINCE OF NEWFOUNDLAND AND   NT 5.125%10          
+          
C63278AX0   CD1001CANFB N 000000  0        1 4  000010000000CAD00Y    
+ CACA  M N
C63278AX0   CD20012003021700020000000000 00000101255000CADF0   N      
+          
C63278AX0   CD3001  00020000000000  320050401                         
+          
C63278AX0   CD5001C AP15 2003021920030219 B RBBR                      
+     N    
C63278AX0   CI00012009070720091229200912140000000072800000000051250000
+0000512500
C63278AX0   CI1001A 000     00000000000000   BN 000000000000000000    
+          
C63278AX0   CR1001    00000000            00000000            00000000
+          
C63278AX0   CX0001C63278AX0         016207268              7546198XS01
+62072689  
C63278AX0   CX4001                                                    
+          
C7631MBG4   CA000120041129C7631MBG4   CI 20090105  A                  
+          
C7631MBG4   CA300120090210 081019 USEST                               
+          
C7631MBG4   CB0001000000512500 N5 200901041199808181999010420080104   
+          
C7631MBG4   CB100100000000 N N            00000001000      EUR   00000
+0000000   
C7631MBG4   CB2001A AF N    C N 0000000000000000 0000000000000000  000
+00000     
C7631MBG4   CB300100000000000 00000000000 00000001000000000000000     
+          
C7631MBG4   CDA001PROVINCE OF QUEBEC                                  
+          
C7631MBG4   CD0001PROVINCE OF QUEBEC             FR 5.125%010409      
+          
C7631MBG4   CD1001CANFB X 000000  0        1 4  000010000000EUR00Y    
+ CACA  M N
C7631MBG4   CD20010000000000063911500000 00000000000000   S0 E        
+          
C7631MBG4   CD3001  00063911500000  320041101                         
+          
C7631MBG4   CD5001       0000000000000000                             
+     N    
C7631MBG4   CI000100000000000000000000000000000000      00000000000000
+0000512500
C7631MBG4   CI1001A 000     00000000000000   BN 000000000000000000    
+          
C7631MBG4   CR1001    00000000            00000000            00000000
+          
C7631MBG4   CX0001C7631MBG4                                           
+          
C7631MBG4   CX4001                                                    
+          
D20658C46   CA000120050707D20658C46   C  00000000  A                  
+          
D20658C46   CA300120090625 180129 USEDT                               
+          
D20658C46   CB0001000000325000 N2 201004091200504012006040920090409FX 
+          
D20658C46   CB100100031362AN N            00000001000EUREUREUR   00000
+0000000   
D20658C46   CB2001A AF N    C N 0000000000000000 0000000000000000  000
+00000     
D20658C46   CB300100000001000000000001000000000001000000000000000     
+          
D20658C46   CC4001F S 0000000000000000    0000000000000000    00000000
+00000000  
D20658C46   CDA001FEDERAL REPUBLIC OF GERMANY                         
+          
D20658C46   CD0001FEDERAL REPUBLIC OF GERMANY    NT-146 3.25%10       
+          
D20658C46   CD1001OUTFBGN 000000  0        1 4  000010000000EUR00Y    
+ DEUS  G N
D20658C46   CD20012005033000700000000000 00000100520000EURF0   N      
+          
D20658C46   CD3001  01700000000000  320090601                         
+          
D20658C46   CD5001C AP15 2005040100000000                             
+     N    
D20658C46   CI000100000000000000000000000000000000      00000000000000
+0000325000
D20658C46   CI1001A 000     00000000000000   BN 000000000000000000    
+          
D20658C46   CR1001    00000000            00000000            00000000
+          
D20658C46   CX0001D20658C46         021609714              B06Y4T2DE00
+01141463  
D20658C46   CX4001                                                    
+          
D20658NG7   CA000120051107D20658NG7   C  00000000  A                  
+          
D20658NG7   CA300120090625 180129 USEDT                               
+          
D20658NG7   CB0001000000537500 N2 201001041199910222001010420090104FX 
+          
D20658NG7   CB100100054227ANDN            00000001000EUREUREUR   00000
+0000000   
D20658NG7   CB2001A AF N    C N 0000000000000000 0000000000000000  000
+00000     
D20658NG7   CB300100000001000000000001000000000001000000000000000     
+          
D20658NG7   CC4001F S 0000000000000000    0000000000000000    00000000
+00000000  
D20658NG7   CDA001FEDERAL REPUBLIC OF GERMANY                         
+          
D20658NG7   CD0001FEDERAL REPUBLIC OF GERMANY    EURO BD 5.375%10     
+          
D20658NG7   CD1001OUTFBGD 000000  0        1 4  000010000000EUR00Y    
+ DEDE  G N
D20658NG7   CD20011999102202000000000000 00000099610000EURF0   N      
+          
D20658NG7   CD3001  00202500000000  320051101                         
+          
D20658NG7   CD5001C AP15 1999102200000000                             
+     N    
D20658NG7   CI000100000000000000000000000000000000      00000000000000
+0000537500
D20658NG7   CI1001A 000     00000000000000   BN 000000000000000000    
+          
D20658NG7   CR1001    00000000            00000000            00000000
+          
D20658NG7   CX0001D20658NG7         010339677              5809343DE00
+01135135  
D20658NG7   CX4001                                                    
+          
D20658SY3   CA000120041118D20658SY3   C  00000000  A                  
+          
D20658SY3   CA300120060601 120347 USEDT                               
+          
D20658SY3   CB0001000000500000 N2 201201041200201042003010420110104   
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D20658SY3   CB100100000000 N N            00000001000      EUR   00000
+0000000   
D20658SY3   CB2001A AF N    C N 0000000000000000 0000000000000000  000
+00000     
D20658SY3   CB300100000000000 00000000000 00000001000000000000000     
+          
D20658SY3   CDA001FEDERAL REPUBLIC OF GERMANY                         
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D20658SY3   CD0001FEDERAL REPUBLIC OF GERMANY    EURO BD 5%12         
+          
D20658SY3   CD1001OUTFBGD 000000  0        1 4  000010000000EUR00Y    
+ DEDE  G N
D20658SY3   CD20010000000000000000000000 00000000000000   S0          
+          
D20658SY3   CD3001  00000000000000   00000000                         
+          
D20658SY3   CD5001       0000000000000000                             
+     N    
D20658SY3   CI000100000000000000000000000000000000      00000000000000
+0000500000
D20658SY3   CI1001A 000     00000000000000   BN 000000000000000000    
+          
D20658SY3   CR1001    00000000            00000000            00000000
+          
D20658SY3   CX0001D20658SY3         014105646              7281466DE00
+01135192  
D20658SY3   CX4001                                                    
+          
D20658YB6   CA000120060725D20658YB6   C  00000000  A
[download]

Thanks everyone for your help. I appreciate it as well as learned something.