how about this sollution 
open FH1, "</users/mhalder/testrun/datafile";

foreach $line (<FH1>){
    
    $line=~s/\s+/:/g;
    ($fileid,$tag)=split (/\:/,$line);

    if (defined $filelist->{$tag}){

         $filelist->{$tag}->{COUNT}++;
         $filelist->{$tag}->{FILES}->[($filelist->{$tag}->{COUNT})-1]=
+$fileid;
     }
    else{
        $filelist->{$tag}->{COUNT}=1;
        $filelist->{$tag}->{FILES}->[($filelist->{$tag}->{COUNT})-1]=$
+fileid;

    }

}

print " **** OUTPUT **** \n\n";

foreach $filetag ( sort keys %$filelist){

    print "\n$filetag: $filelist->{$filetag}->{'COUNT'} FILES\n\n";
     print "LIST OF FILES:\n";
 
     foreach $filename ( @{$filelist->{$filetag}->{FILES}}){
           print " $filename\n";
     }
 
     print;
 
 
}

[download]



in my code "datafile" holds the lines 1300018 a1
1300019 a1
1300100 a2
1300101 a2
1300126 a2
1300127 a2
1300128 a2
1300129 a2
1300130 a3
1300131 a3
1300132 a3
1300133 a3

In reply to Re: question about algorithm by perlplayer
in thread question about algorithm by cxfcxf

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