I have a file with around 3000 lines in it. With this I need to create about 1500 separate files, each containing 2 lines. The lines in outputfile 1 should be line 1 and 2 from the inputfile; the lines in outputfile 2 should be line 3 and 4 from the inputfile and so on... So each line has to be written exactly once (no more, no less) and I have to be sure the order of the lines written is respected. The code I have written to work this way splits up the big file in small files, but it only writes 1 line to each file.

I have tried using File::CountLines to make the loop stop at 2 lines and open a new outputfile, but this only confused myself... the linecounter seemed to be stuck on either 0 or 1, writing the same line to an infinite number of files, or even worse: kept filling the same file in an endless loop, making the file too big to open very quickly. So I quickly threw this option out the window.

If this is the code I need to work on, this is it:

#!perl

use strict;
use warnings; 
use autodie; # die if problem reading or writing a file
use feature qw(say);

my $input = "C:/Some/specific/path/to/file.txt";

open FILEin, $input;
my @input = <FILEin>;
binmode(FILEin);
undef $/;

foreach $input (@input) {
    my $dir = 'C:/Some/specific/folder';
    my @files = <$dir/*>;
    my $countf = @files;
    my $outfile = $dir.'/bladibla_'.$countf.'.txt';
        open FILEout, '>'.$outfile;
        print FILEout $input;
        close FILEout;
        say 'Wrote '.$input.' to '.$outfile;
}
    
close FILEin;
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The other code is an attempt at working the other way around.

I let the first code do what it does to end up with the 3000 files with each containing 1 line. The files contain a counter in the filename which is reliable, meaning: outputfile 1 should contain the contents of inputfile 0 and 1; outputfile 2 should contain the contents of inputfile 2 and 3 and so on...

The problem with the code I have written for this is that it doesn't seem to loop, it writes 1 file and then stops. The written file is correct (contains the contents of the first 2 inputfiles), but it should do this for all files found in the inputfolder. I know there is a problem with my 'for'-loop, but it seems I am not experienced enough to figure out what it should be.

If I better keep working on this code, here it is:

#!perl

use strict;
use warnings; 
use autodie; # die if problem reading or writing a file
use feature qw(say);

my $inbase = 'C:/Some/specific/folder';
my $outbase = 'C:/Some/other/specific/folder';
my $counter = @ARGV;

for my $file ($inbase.'/bladibla_'.$counter.'.txt') {

    my @outfiles = <$outbase/*>;
    my $countf = @outfiles;
    my $outfile = $outbase.'/bladibla_'.$countf.'.txt';
    
    open FILEout, '>'.$outfile;
    
    my $file = ($inbase.'/bladibla_'.$counter.'.txt');
        open FILEin, $file;
        my $contents = <FILEin>;
        binmode(FILEin);
    print FILEout $contents;
    close FILEin;
    
    say 'Wrote '.$contents.' to '.$outfile;
    
    $counter += 1;
    
    my $file2 = ($inbase.'/bladibla_'.$counter.'.txt');
        open FILEin, $file2;
        my $contents2 = <FILEin>;
        binmode(FILEin);
    print FILEout $contents2;
    close FILEin;
    
    say 'Wrote '.$contents2.' to '.$outfile;
    
    close FILEout;
    
    $counter += 1;
}
[download]

I'm sure both codes can be tweaked to do exactly what I need it to do, just pick the one you think needs the least/easiest work.